Merge commit 'linus/master' into tracing/kprobes

Conflicts:
	kernel/trace/Makefile
	kernel/trace/trace.h
	kernel/trace/trace_event_types.h
	kernel/trace/trace_export.c

Merge reason:
	Sync with latest significant tracing core changes.

7 files changed, 1288 insertions, 32 deletions

diff --git a/Documentation/trace/events-kmem.txt b/Documentation/trace/events-kmem.txt
new file mode 100644
index 000000000000..6ef2a8652e17
--- /dev/null
+++ b/Documentation/trace/events-kmem.txt
@@ -0,0 +1,107 @@
+                        Subsystem Trace Points: kmem
+
+The tracing system kmem captures events related to object and page allocation
+within the kernel. Broadly speaking there are four major subheadings.
+
+  o Slab allocation of small objects of unknown type (kmalloc)
+  o Slab allocation of small objects of known type
+  o Page allocation
+  o Per-CPU Allocator Activity
+  o External Fragmentation
+
+This document will describe what each of the tracepoints are and why they
+might be useful.
+
+1. Slab allocation of small objects of unknown type
+===================================================
+kmalloc         call_site=%lx ptr=%p bytes_req=%zu bytes_alloc=%zu gfp_flags=%s
+kmalloc_node    call_site=%lx ptr=%p bytes_req=%zu bytes_alloc=%zu gfp_flags=%s node=%d
+kfree           call_site=%lx ptr=%p
+
+Heavy activity for these events may indicate that a specific cache is
+justified, particularly if kmalloc slab pages are getting significantly
+internal fragmented as a result of the allocation pattern. By correlating
+kmalloc with kfree, it may be possible to identify memory leaks and where
+the allocation sites were.
+
+
+2. Slab allocation of small objects of known type
+=================================================
+kmem_cache_alloc        call_site=%lx ptr=%p bytes_req=%zu bytes_alloc=%zu gfp_flags=%s
+kmem_cache_alloc_node   call_site=%lx ptr=%p bytes_req=%zu bytes_alloc=%zu gfp_flags=%s node=%d
+kmem_cache_free         call_site=%lx ptr=%p
+
+These events are similar in usage to the kmalloc-related events except that
+it is likely easier to pin the event down to a specific cache. At the time
+of writing, no information is available on what slab is being allocated from,
+but the call_site can usually be used to extrapolate that information
+
+3. Page allocation
+==================
+mm_page_alloc             page=%p pfn=%lu order=%d migratetype=%d gfp_flags=%s
+mm_page_alloc_zone_locked page=%p pfn=%lu order=%u migratetype=%d cpu=%d percpu_refill=%d
+mm_page_free_direct       page=%p pfn=%lu order=%d
+mm_pagevec_free           page=%p pfn=%lu order=%d cold=%d
+
+These four events deal with page allocation and freeing. mm_page_alloc is
+a simple indicator of page allocator activity. Pages may be allocated from
+the per-CPU allocator (high performance) or the buddy allocator.
+
+If pages are allocated directly from the buddy allocator, the
+mm_page_alloc_zone_locked event is triggered. This event is important as high
+amounts of activity imply high activity on the zone->lock. Taking this lock
+impairs performance by disabling interrupts, dirtying cache lines between
+CPUs and serialising many CPUs.
+
+When a page is freed directly by the caller, the mm_page_free_direct event
+is triggered. Significant amounts of activity here could indicate that the
+callers should be batching their activities.
+
+When pages are freed using a pagevec, the mm_pagevec_free is
+triggered. Broadly speaking, pages are taken off the LRU lock in bulk and
+freed in batch with a pagevec. Significant amounts of activity here could
+indicate that the system is under memory pressure and can also indicate
+contention on the zone->lru_lock.
+
+4. Per-CPU Allocator Activity
+=============================
+mm_page_alloc_zone_locked       page=%p pfn=%lu order=%u migratetype=%d cpu=%d percpu_refill=%d
+mm_page_pcpu_drain              page=%p pfn=%lu order=%d cpu=%d migratetype=%d
+
+In front of the page allocator is a per-cpu page allocator. It exists only
+for order-0 pages, reduces contention on the zone->lock and reduces the
+amount of writing on struct page.
+
+When a per-CPU list is empty or pages of the wrong type are allocated,
+the zone->lock will be taken once and the per-CPU list refilled. The event
+triggered is mm_page_alloc_zone_locked for each page allocated with the
+event indicating whether it is for a percpu_refill or not.
+
+When the per-CPU list is too full, a number of pages are freed, each one
+which triggers a mm_page_pcpu_drain event.
+
+The individual nature of the events are so that pages can be tracked
+between allocation and freeing. A number of drain or refill pages that occur
+consecutively imply the zone->lock being taken once. Large amounts of PCP
+refills and drains could imply an imbalance between CPUs where too much work
+is being concentrated in one place. It could also indicate that the per-CPU
+lists should be a larger size. Finally, large amounts of refills on one CPU
+and drains on another could be a factor in causing large amounts of cache
+line bounces due to writes between CPUs and worth investigating if pages
+can be allocated and freed on the same CPU through some algorithm change.
+
+5. External Fragmentation
+=========================
+mm_page_alloc_extfrag           page=%p pfn=%lu alloc_order=%d fallback_order=%d pageblock_order=%d alloc_migratetype=%d fallback_migratetype=%d fragmenting=%d change_ownership=%d
+
+External fragmentation affects whether a high-order allocation will be
+successful or not. For some types of hardware, this is important although
+it is avoided where possible. If the system is using huge pages and needs
+to be able to resize the pool over the lifetime of the system, this value
+is important.
+
+Large numbers of this event implies that memory is fragmenting and
+high-order allocations will start failing at some time in the future. One
+means of reducing the occurange of this event is to increase the size of
+min_free_kbytes in increments of 3*pageblock_size*nr_online_nodes where
+pageblock_size is usually the size of the default hugepage size.
diff --git a/Documentation/trace/events.txt b/Documentation/trace/events.txt
index 2bcc8d4dea29..02ac6ed38b2d 100644
--- a/Documentation/trace/events.txt
+++ b/Documentation/trace/events.txt
@@ -1,7 +1,7 @@
                              Event Tracing
 
                 Documentation written by Theodore Ts'o
-                        Updated by Li Zefan
+                Updated by Li Zefan and Tom Zanussi
 
 1. Introduction
 ===============
@@ -22,12 +22,12 @@ tracing information should be printed.
 ---------------------------------
 
 The events which are available for tracing can be found in the file
-/debug/tracing/available_events.
+/sys/kernel/debug/tracing/available_events.
 
 To enable a particular event, such as 'sched_wakeup', simply echo it
-to /debug/tracing/set_event. For example:
+to /sys/kernel/debug/tracing/set_event. For example:
 
-        # echo sched_wakeup >> /debug/tracing/set_event
+        # echo sched_wakeup >> /sys/kernel/debug/tracing/set_event
 
 [ Note: '>>' is necessary, otherwise it will firstly disable
   all the events. ]
@@ -35,15 +35,15 @@ to /debug/tracing/set_event. For example:
 To disable an event, echo the event name to the set_event file prefixed
 with an exclamation point:
 
-        # echo '!sched_wakeup' >> /debug/tracing/set_event
+        # echo '!sched_wakeup' >> /sys/kernel/debug/tracing/set_event
 
 To disable all events, echo an empty line to the set_event file:
 
-        # echo > /debug/tracing/set_event
+        # echo > /sys/kernel/debug/tracing/set_event
 
 To enable all events, echo '*:*' or '*:' to the set_event file:
 
-        # echo *:* > /debug/tracing/set_event
+        # echo *:* > /sys/kernel/debug/tracing/set_event
 
 The events are organized into subsystems, such as ext4, irq, sched,
 etc., and a full event name looks like this: <subsystem>:<event>.  The
@@ -52,29 +52,29 @@ file.  All of the events in a subsystem can be specified via the syntax
 "<subsystem>:*"; for example, to enable all irq events, you can use the
 command:
 
-        # echo 'irq:*' > /debug/tracing/set_event
+        # echo 'irq:*' > /sys/kernel/debug/tracing/set_event
 
 2.2 Via the 'enable' toggle
 ---------------------------
 
-The events available are also listed in /debug/tracing/events/ hierarchy
+The events available are also listed in /sys/kernel/debug/tracing/events/ hierarchy
 of directories.
 
 To enable event 'sched_wakeup':
 
-        # echo 1 > /debug/tracing/events/sched/sched_wakeup/enable
+        # echo 1 > /sys/kernel/debug/tracing/events/sched/sched_wakeup/enable
 
 To disable it:
 
-        # echo 0 > /debug/tracing/events/sched/sched_wakeup/enable
+        # echo 0 > /sys/kernel/debug/tracing/events/sched/sched_wakeup/enable
 
 To enable all events in sched subsystem:
 
-        # echo 1 > /debug/tracing/events/sched/enable
+        # echo 1 > /sys/kernel/debug/tracing/events/sched/enable
 
-To eanble all events:
+To enable all events:
 
-        # echo 1 > /debug/tracing/events/enable
+        # echo 1 > /sys/kernel/debug/tracing/events/enable
 
 When reading one of these enable files, there are four results:
 
@@ -97,3 +97,185 @@ The format of this boot option is the same as described in section 2.1.
 
 See The example provided in samples/trace_events
 
+4. Event formats
+================
+
+Each trace event has a 'format' file associated with it that contains
+a description of each field in a logged event.  This information can
+be used to parse the binary trace stream, and is also the place to
+find the field names that can be used in event filters (see section 5).
+
+It also displays the format string that will be used to print the
+event in text mode, along with the event name and ID used for
+profiling.
+
+Every event has a set of 'common' fields associated with it; these are
+the fields prefixed with 'common_'.  The other fields vary between
+events and correspond to the fields defined in the TRACE_EVENT
+definition for that event.
+
+Each field in the format has the form:
+
+     field:field-type field-name; offset:N; size:N;
+
+where offset is the offset of the field in the trace record and size
+is the size of the data item, in bytes.
+
+For example, here's the information displayed for the 'sched_wakeup'
+event:
+
+# cat /debug/tracing/events/sched/sched_wakeup/format
+
+name: sched_wakeup
+ID: 60
+format:
+        field:unsigned short common_type;       offset:0;       size:2;
+        field:unsigned char common_flags;       offset:2;       size:1;
+        field:unsigned char common_preempt_count;       offset:3;       size:1;
+        field:int common_pid;   offset:4;       size:4;
+        field:int common_tgid;  offset:8;       size:4;
+
+        field:char comm[TASK_COMM_LEN]; offset:12;      size:16;
+        field:pid_t pid;        offset:28;      size:4;
+        field:int prio; offset:32;      size:4;
+        field:int success;      offset:36;      size:4;
+        field:int cpu;  offset:40;      size:4;
+
+print fmt: "task %s:%d [%d] success=%d [%03d]", REC->comm, REC->pid,
+           REC->prio, REC->success, REC->cpu
+
+This event contains 10 fields, the first 5 common and the remaining 5
+event-specific.  All the fields for this event are numeric, except for
+'comm' which is a string, a distinction important for event filtering.
+
+5. Event filtering
+==================
+
+Trace events can be filtered in the kernel by associating boolean
+'filter expressions' with them.  As soon as an event is logged into
+the trace buffer, its fields are checked against the filter expression
+associated with that event type.  An event with field values that
+'match' the filter will appear in the trace output, and an event whose
+values don't match will be discarded.  An event with no filter
+associated with it matches everything, and is the default when no
+filter has been set for an event.
+
+5.1 Expression syntax
+---------------------
+
+A filter expression consists of one or more 'predicates' that can be
+combined using the logical operators '&&' and '||'.  A predicate is
+simply a clause that compares the value of a field contained within a
+logged event with a constant value and returns either 0 or 1 depending
+on whether the field value matched (1) or didn't match (0):
+
+          field-name relational-operator value
+
+Parentheses can be used to provide arbitrary logical groupings and
+double-quotes can be used to prevent the shell from interpreting
+operators as shell metacharacters.
+
+The field-names available for use in filters can be found in the
+'format' files for trace events (see section 4).
+
+The relational-operators depend on the type of the field being tested:
+
+The operators available for numeric fields are:
+
+==, !=, <, <=, >, >=
+
+And for string fields they are:
+
+==, !=
+
+Currently, only exact string matches are supported.
+
+Currently, the maximum number of predicates in a filter is 16.
+
+5.2 Setting filters
+-------------------
+
+A filter for an individual event is set by writing a filter expression
+to the 'filter' file for the given event.
+
+For example:
+
+# cd /debug/tracing/events/sched/sched_wakeup
+# echo "common_preempt_count > 4" > filter
+
+A slightly more involved example:
+
+# cd /debug/tracing/events/sched/sched_signal_send
+# echo "((sig >= 10 && sig < 15) || sig == 17) && comm != bash" > filter
+
+If there is an error in the expression, you'll get an 'Invalid
+argument' error when setting it, and the erroneous string along with
+an error message can be seen by looking at the filter e.g.:
+
+# cd /debug/tracing/events/sched/sched_signal_send
+# echo "((sig >= 10 && sig < 15) || dsig == 17) && comm != bash" > filter
+-bash: echo: write error: Invalid argument
+# cat filter
+((sig >= 10 && sig < 15) || dsig == 17) && comm != bash
+^
+parse_error: Field not found
+
+Currently the caret ('^') for an error always appears at the beginning of
+the filter string; the error message should still be useful though
+even without more accurate position info.
+
+5.3 Clearing filters
+--------------------
+
+To clear the filter for an event, write a '0' to the event's filter
+file.
+
+To clear the filters for all events in a subsystem, write a '0' to the
+subsystem's filter file.
+
+5.3 Subsystem filters
+---------------------
+
+For convenience, filters for every event in a subsystem can be set or
+cleared as a group by writing a filter expression into the filter file
+at the root of the subsytem.  Note however, that if a filter for any
+event within the subsystem lacks a field specified in the subsystem
+filter, or if the filter can't be applied for any other reason, the
+filter for that event will retain its previous setting.  This can
+result in an unintended mixture of filters which could lead to
+confusing (to the user who might think different filters are in
+effect) trace output.  Only filters that reference just the common
+fields can be guaranteed to propagate successfully to all events.
+
+Here are a few subsystem filter examples that also illustrate the
+above points:
+
+Clear the filters on all events in the sched subsytem:
+
+# cd /sys/kernel/debug/tracing/events/sched
+# echo 0 > filter
+# cat sched_switch/filter
+none
+# cat sched_wakeup/filter
+none
+
+Set a filter using only common fields for all events in the sched
+subsytem (all events end up with the same filter):
+
+# cd /sys/kernel/debug/tracing/events/sched
+# echo common_pid == 0 > filter
+# cat sched_switch/filter
+common_pid == 0
+# cat sched_wakeup/filter
+common_pid == 0
+
+Attempt to set a filter using a non-common field for all events in the
+sched subsytem (all events but those that have a prev_pid field retain
+their old filters):
+
+# cd /sys/kernel/debug/tracing/events/sched
+# echo prev_pid == 0 > filter
+# cat sched_switch/filter
+prev_pid == 0
+# cat sched_wakeup/filter
+common_pid == 0
diff --git a/Documentation/trace/ftrace-design.txt b/Documentation/trace/ftrace-design.txt
new file mode 100644
index 000000000000..7003e10f10f5
--- /dev/null
+++ b/Documentation/trace/ftrace-design.txt
@@ -0,0 +1,233 @@
+                function tracer guts
+                ====================
+
+Introduction
+------------
+
+Here we will cover the architecture pieces that the common function tracing
+code relies on for proper functioning.  Things are broken down into increasing
+complexity so that you can start simple and at least get basic functionality.
+
+Note that this focuses on architecture implementation details only.  If you
+want more explanation of a feature in terms of common code, review the common
+ftrace.txt file.
+
+
+Prerequisites
+-------------
+
+Ftrace relies on these features being implemented:
+ STACKTRACE_SUPPORT - implement save_stack_trace()
+ TRACE_IRQFLAGS_SUPPORT - implement include/asm/irqflags.h
+
+
+HAVE_FUNCTION_TRACER
+--------------------
+
+You will need to implement the mcount and the ftrace_stub functions.
+
+The exact mcount symbol name will depend on your toolchain.  Some call it
+"mcount", "_mcount", or even "__mcount".  You can probably figure it out by
+running something like:
+        $ echo 'main(){}' | gcc -x c -S -o - - -pg | grep mcount
+                call    mcount
+We'll make the assumption below that the symbol is "mcount" just to keep things
+nice and simple in the examples.
+
+Keep in mind that the ABI that is in effect inside of the mcount function is
+*highly* architecture/toolchain specific.  We cannot help you in this regard,
+sorry.  Dig up some old documentation and/or find someone more familiar than
+you to bang ideas off of.  Typically, register usage (argument/scratch/etc...)
+is a major issue at this point, especially in relation to the location of the
+mcount call (before/after function prologue).  You might also want to look at
+how glibc has implemented the mcount function for your architecture.  It might
+be (semi-)relevant.
+
+The mcount function should check the function pointer ftrace_trace_function
+to see if it is set to ftrace_stub.  If it is, there is nothing for you to do,
+so return immediately.  If it isn't, then call that function in the same way
+the mcount function normally calls __mcount_internal -- the first argument is
+the "frompc" while the second argument is the "selfpc" (adjusted to remove the
+size of the mcount call that is embedded in the function).
+
+For example, if the function foo() calls bar(), when the bar() function calls
+mcount(), the arguments mcount() will pass to the tracer are:
+        "frompc" - the address bar() will use to return to foo()
+        "selfpc" - the address bar() (with _mcount() size adjustment)
+
+Also keep in mind that this mcount function will be called *a lot*, so
+optimizing for the default case of no tracer will help the smooth running of
+your system when tracing is disabled.  So the start of the mcount function is
+typically the bare min with checking things before returning.  That also means
+the code flow should usually kept linear (i.e. no branching in the nop case).
+This is of course an optimization and not a hard requirement.
+
+Here is some pseudo code that should help (these functions should actually be
+implemented in assembly):
+
+void ftrace_stub(void)
+{
+        return;
+}
+
+void mcount(void)
+{
+        /* save any bare state needed in order to do initial checking */
+
+        extern void (*ftrace_trace_function)(unsigned long, unsigned long);
+        if (ftrace_trace_function != ftrace_stub)
+                goto do_trace;
+
+        /* restore any bare state */
+
+        return;
+
+do_trace:
+
+        /* save all state needed by the ABI (see paragraph above) */
+
+        unsigned long frompc = ...;
+        unsigned long selfpc = <return address> - MCOUNT_INSN_SIZE;
+        ftrace_trace_function(frompc, selfpc);
+
+        /* restore all state needed by the ABI */
+}
+
+Don't forget to export mcount for modules !
+extern void mcount(void);
+EXPORT_SYMBOL(mcount);
+
+
+HAVE_FUNCTION_TRACE_MCOUNT_TEST
+-------------------------------
+
+This is an optional optimization for the normal case when tracing is turned off
+in the system.  If you do not enable this Kconfig option, the common ftrace
+code will take care of doing the checking for you.
+
+To support this feature, you only need to check the function_trace_stop
+variable in the mcount function.  If it is non-zero, there is no tracing to be
+done at all, so you can return.
+
+This additional pseudo code would simply be:
+void mcount(void)
+{
+        /* save any bare state needed in order to do initial checking */
+
++       if (function_trace_stop)
++               return;
+
+        extern void (*ftrace_trace_function)(unsigned long, unsigned long);
+        if (ftrace_trace_function != ftrace_stub)
+...
+
+
+HAVE_FUNCTION_GRAPH_TRACER
+--------------------------
+
+Deep breath ... time to do some real work.  Here you will need to update the
+mcount function to check ftrace graph function pointers, as well as implement
+some functions to save (hijack) and restore the return address.
+
+The mcount function should check the function pointers ftrace_graph_return
+(compare to ftrace_stub) and ftrace_graph_entry (compare to
+ftrace_graph_entry_stub).  If either of those are not set to the relevant stub
+function, call the arch-specific function ftrace_graph_caller which in turn
+calls the arch-specific function prepare_ftrace_return.  Neither of these
+function names are strictly required, but you should use them anyways to stay
+consistent across the architecture ports -- easier to compare & contrast
+things.
+
+The arguments to prepare_ftrace_return are slightly different than what are
+passed to ftrace_trace_function.  The second argument "selfpc" is the same,
+but the first argument should be a pointer to the "frompc".  Typically this is
+located on the stack.  This allows the function to hijack the return address
+temporarily to have it point to the arch-specific function return_to_handler.
+That function will simply call the common ftrace_return_to_handler function and
+that will return the original return address with which, you can return to the
+original call site.
+
+Here is the updated mcount pseudo code:
+void mcount(void)
+{
+...
+        if (ftrace_trace_function != ftrace_stub)
+                goto do_trace;
+
++#ifdef CONFIG_FUNCTION_GRAPH_TRACER
++       extern void (*ftrace_graph_return)(...);
++       extern void (*ftrace_graph_entry)(...);
++       if (ftrace_graph_return != ftrace_stub ||
++           ftrace_graph_entry != ftrace_graph_entry_stub)
++               ftrace_graph_caller();
++#endif
+
+        /* restore any bare state */
+...
+
+Here is the pseudo code for the new ftrace_graph_caller assembly function:
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+void ftrace_graph_caller(void)
+{
+        /* save all state needed by the ABI */
+
+        unsigned long *frompc = &...;
+        unsigned long selfpc = <return address> - MCOUNT_INSN_SIZE;
+        prepare_ftrace_return(frompc, selfpc);
+
+        /* restore all state needed by the ABI */
+}
+#endif
+
+For information on how to implement prepare_ftrace_return(), simply look at
+the x86 version.  The only architecture-specific piece in it is the setup of
+the fault recovery table (the asm(...) code).  The rest should be the same
+across architectures.
+
+Here is the pseudo code for the new return_to_handler assembly function.  Note
+that the ABI that applies here is different from what applies to the mcount
+code.  Since you are returning from a function (after the epilogue), you might
+be able to skimp on things saved/restored (usually just registers used to pass
+return values).
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+void return_to_handler(void)
+{
+        /* save all state needed by the ABI (see paragraph above) */
+
+        void (*original_return_point)(void) = ftrace_return_to_handler();
+
+        /* restore all state needed by the ABI */
+
+        /* this is usually either a return or a jump */
+        original_return_point();
+}
+#endif
+
+
+HAVE_FTRACE_NMI_ENTER
+---------------------
+
+If you can't trace NMI functions, then skip this option.
+
+<details to be filled>
+
+
+HAVE_FTRACE_SYSCALLS
+---------------------
+
+<details to be filled>
+
+
+HAVE_FTRACE_MCOUNT_RECORD
+-------------------------
+
+See scripts/recordmcount.pl for more info.
+
+<details to be filled>
+
+
+HAVE_DYNAMIC_FTRACE
+---------------------
+
+<details to be filled>
diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index 355d0f1f8c50..957b22fde2df 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -26,6 +26,12 @@ disabled, and more (ftrace allows for tracer plugins, which
 means that the list of tracers can always grow).
 
 
+Implementation Details
+----------------------
+
+See ftrace-design.txt for details for arch porters and such.
+
+
 The File System
 ---------------
 
@@ -127,7 +133,7 @@ of ftrace. Here is a list of some of the key files:
         than requested, the rest of the page will be used,
         making the actual allocation bigger than requested.
         ( Note, the size may not be a multiple of the page size
-          due to buffer managment overhead. )
+          due to buffer management overhead. )
 
         This can only be updated when the current_tracer
         is set to "nop".
diff --git a/Documentation/trace/postprocess/trace-pagealloc-postprocess.pl b/Documentation/trace/postprocess/trace-pagealloc-postprocess.pl
new file mode 100644
index 000000000000..7df50e8cf4d9
--- /dev/null
+++ b/Documentation/trace/postprocess/trace-pagealloc-postprocess.pl
@@ -0,0 +1,418 @@
+#!/usr/bin/perl
+# This is a POC (proof of concept or piece of crap, take your pick) for reading the
+# text representation of trace output related to page allocation. It makes an attempt
+# to extract some high-level information on what is going on. The accuracy of the parser
+# may vary considerably
+#
+# Example usage: trace-pagealloc-postprocess.pl < /sys/kernel/debug/tracing/trace_pipe
+# other options
+#   --prepend-parent    Report on the parent proc and PID
+#   --read-procstat     If the trace lacks process info, get it from /proc
+#   --ignore-pid        Aggregate processes of the same name together
+#
+# Copyright (c) IBM Corporation 2009
+# Author: Mel Gorman <mel@csn.ul.ie>
+use strict;
+use Getopt::Long;
+
+# Tracepoint events
+use constant MM_PAGE_ALLOC              => 1;
+use constant MM_PAGE_FREE_DIRECT        => 2;
+use constant MM_PAGEVEC_FREE            => 3;
+use constant MM_PAGE_PCPU_DRAIN         => 4;
+use constant MM_PAGE_ALLOC_ZONE_LOCKED  => 5;
+use constant MM_PAGE_ALLOC_EXTFRAG      => 6;
+use constant EVENT_UNKNOWN              => 7;
+
+# Constants used to track state
+use constant STATE_PCPU_PAGES_DRAINED   => 8;
+use constant STATE_PCPU_PAGES_REFILLED  => 9;
+
+# High-level events extrapolated from tracepoints
+use constant HIGH_PCPU_DRAINS           => 10;
+use constant HIGH_PCPU_REFILLS          => 11;
+use constant HIGH_EXT_FRAGMENT          => 12;
+use constant HIGH_EXT_FRAGMENT_SEVERE   => 13;
+use constant HIGH_EXT_FRAGMENT_MODERATE => 14;
+use constant HIGH_EXT_FRAGMENT_CHANGED  => 15;
+
+my %perprocesspid;
+my %perprocess;
+my $opt_ignorepid;
+my $opt_read_procstat;
+my $opt_prepend_parent;
+
+# Catch sigint and exit on request
+my $sigint_report = 0;
+my $sigint_exit = 0;
+my $sigint_pending = 0;
+my $sigint_received = 0;
+sub sigint_handler {
+        my $current_time = time;
+        if ($current_time - 2 > $sigint_received) {
+                print "SIGINT received, report pending. Hit ctrl-c again to exit\n";
+                $sigint_report = 1;
+        } else {
+                if (!$sigint_exit) {
+                        print "Second SIGINT received quickly, exiting\n";
+                }
+                $sigint_exit++;
+        }
+
+        if ($sigint_exit > 3) {
+                print "Many SIGINTs received, exiting now without report\n";
+                exit;
+        }
+
+        $sigint_received = $current_time;
+        $sigint_pending = 1;
+}
+$SIG{INT} = "sigint_handler";
+
+# Parse command line options
+GetOptions(
+        'ignore-pid'     =>     \$opt_ignorepid,
+        'read-procstat'  =>     \$opt_read_procstat,
+        'prepend-parent' =>     \$opt_prepend_parent,
+);
+
+# Defaults for dynamically discovered regex's
+my $regex_fragdetails_default = 'page=([0-9a-f]*) pfn=([0-9]*) alloc_order=([-0-9]*) fallback_order=([-0-9]*) pageblock_order=([-0-9]*) alloc_migratetype=([-0-9]*) fallback_migratetype=([-0-9]*) fragmenting=([-0-9]) change_ownership=([-0-9])';
+
+# Dyanically discovered regex
+my $regex_fragdetails;
+
+# Static regex used. Specified like this for readability and for use with /o
+#                      (process_pid)     (cpus      )   ( time  )   (tpoint    ) (details)
+my $regex_traceevent = '\s*([a-zA-Z0-9-]*)\s*(\[[0-9]*\])\s*([0-9.]*):\s*([a-zA-Z_]*):\s*(.*)';
+my $regex_statname = '[-0-9]*\s\((.*)\).*';
+my $regex_statppid = '[-0-9]*\s\(.*\)\s[A-Za-z]\s([0-9]*).*';
+
+sub generate_traceevent_regex {
+        my $event = shift;
+        my $default = shift;
+        my $regex;
+
+        # Read the event format or use the default
+        if (!open (FORMAT, "/sys/kernel/debug/tracing/events/$event/format")) {
+                $regex = $default;
+        } else {
+                my $line;
+                while (!eof(FORMAT)) {
+                        $line = <FORMAT>;
+                        if ($line =~ /^print fmt:\s"(.*)",.*/) {
+                                $regex = $1;
+                                $regex =~ s/%p/\([0-9a-f]*\)/g;
+                                $regex =~ s/%d/\([-0-9]*\)/g;
+                                $regex =~ s/%lu/\([0-9]*\)/g;
+                        }
+                }
+        }
+
+        # Verify fields are in the right order
+        my $tuple;
+        foreach $tuple (split /\s/, $regex) {
+                my ($key, $value) = split(/=/, $tuple);
+                my $expected = shift;
+                if ($key ne $expected) {
+                        print("WARNING: Format not as expected '$key' != '$expected'");
+                        $regex =~ s/$key=\((.*)\)/$key=$1/;
+                }
+        }
+
+        if (defined shift) {
+                die("Fewer fields than expected in format");
+        }
+
+        return $regex;
+}
+$regex_fragdetails = generate_traceevent_regex("kmem/mm_page_alloc_extfrag",
+                        $regex_fragdetails_default,
+                        "page", "pfn",
+                        "alloc_order", "fallback_order", "pageblock_order",
+                        "alloc_migratetype", "fallback_migratetype",
+                        "fragmenting", "change_ownership");
+
+sub read_statline($) {
+        my $pid = $_[0];
+        my $statline;
+
+        if (open(STAT, "/proc/$pid/stat")) {
+                $statline = <STAT>;
+                close(STAT);
+        }
+
+        if ($statline eq '') {
+                $statline = "-1 (UNKNOWN_PROCESS_NAME) R 0";
+        }
+
+        return $statline;
+}
+
+sub guess_process_pid($$) {
+        my $pid = $_[0];
+        my $statline = $_[1];
+
+        if ($pid == 0) {
+                return "swapper-0";
+        }
+
+        if ($statline !~ /$regex_statname/o) {
+                die("Failed to math stat line for process name :: $statline");
+        }
+        return "$1-$pid";
+}
+
+sub parent_info($$) {
+        my $pid = $_[0];
+        my $statline = $_[1];
+        my $ppid;
+
+        if ($pid == 0) {
+                return "NOPARENT-0";
+        }
+
+        if ($statline !~ /$regex_statppid/o) {
+                die("Failed to match stat line process ppid:: $statline");
+        }
+
+        # Read the ppid stat line
+        $ppid = $1;
+        return guess_process_pid($ppid, read_statline($ppid));
+}
+
+sub process_events {
+        my $traceevent;
+        my $process_pid;
+        my $cpus;
+        my $timestamp;
+        my $tracepoint;
+        my $details;
+        my $statline;
+
+        # Read each line of the event log
+EVENT_PROCESS:
+        while ($traceevent = <STDIN>) {
+                if ($traceevent =~ /$regex_traceevent/o) {
+                        $process_pid = $1;
+                        $tracepoint = $4;
+
+                        if ($opt_read_procstat || $opt_prepend_parent) {
+                                $process_pid =~ /(.*)-([0-9]*)$/;
+                                my $process = $1;
+                                my $pid = $2;
+
+                                $statline = read_statline($pid);
+
+                                if ($opt_read_procstat && $process eq '') {
+                                        $process_pid = guess_process_pid($pid, $statline);
+                                }
+
+                                if ($opt_prepend_parent) {
+                                        $process_pid = parent_info($pid, $statline) . " :: $process_pid";
+                                }
+                        }
+
+                        # Unnecessary in this script. Uncomment if required
+                        # $cpus = $2;
+                        # $timestamp = $3;
+                } else {
+                        next;
+                }
+
+                # Perl Switch() sucks majorly
+                if ($tracepoint eq "mm_page_alloc") {
+                        $perprocesspid{$process_pid}->{MM_PAGE_ALLOC}++;
+                } elsif ($tracepoint eq "mm_page_free_direct") {
+                        $perprocesspid{$process_pid}->{MM_PAGE_FREE_DIRECT}++;
+                } elsif ($tracepoint eq "mm_pagevec_free") {
+                        $perprocesspid{$process_pid}->{MM_PAGEVEC_FREE}++;
+                } elsif ($tracepoint eq "mm_page_pcpu_drain") {
+                        $perprocesspid{$process_pid}->{MM_PAGE_PCPU_DRAIN}++;
+                        $perprocesspid{$process_pid}->{STATE_PCPU_PAGES_DRAINED}++;
+                } elsif ($tracepoint eq "mm_page_alloc_zone_locked") {
+                        $perprocesspid{$process_pid}->{MM_PAGE_ALLOC_ZONE_LOCKED}++;
+                        $perprocesspid{$process_pid}->{STATE_PCPU_PAGES_REFILLED}++;
+                } elsif ($tracepoint eq "mm_page_alloc_extfrag") {
+
+                        # Extract the details of the event now
+                        $details = $5;
+
+                        my ($page, $pfn);
+                        my ($alloc_order, $fallback_order, $pageblock_order);
+                        my ($alloc_migratetype, $fallback_migratetype);
+                        my ($fragmenting, $change_ownership);
+
+                        if ($details !~ /$regex_fragdetails/o) {
+                                print "WARNING: Failed to parse mm_page_alloc_extfrag as expected\n";
+                                next;
+                        }
+
+                        $perprocesspid{$process_pid}->{MM_PAGE_ALLOC_EXTFRAG}++;
+                        $page = $1;
+                        $pfn = $2;
+                        $alloc_order = $3;
+                        $fallback_order = $4;
+                        $pageblock_order = $5;
+                        $alloc_migratetype = $6;
+                        $fallback_migratetype = $7;
+                        $fragmenting = $8;
+                        $change_ownership = $9;
+
+                        if ($fragmenting) {
+                                $perprocesspid{$process_pid}->{HIGH_EXT_FRAG}++;
+                                if ($fallback_order <= 3) {
+                                        $perprocesspid{$process_pid}->{HIGH_EXT_FRAGMENT_SEVERE}++;
+                                } else {
+                                        $perprocesspid{$process_pid}->{HIGH_EXT_FRAGMENT_MODERATE}++;
+                                }
+                        }
+                        if ($change_ownership) {
+                                $perprocesspid{$process_pid}->{HIGH_EXT_FRAGMENT_CHANGED}++;
+                        }
+                } else {
+                        $perprocesspid{$process_pid}->{EVENT_UNKNOWN}++;
+                }
+
+                # Catch a full pcpu drain event
+                if ($perprocesspid{$process_pid}->{STATE_PCPU_PAGES_DRAINED} &&
+                                $tracepoint ne "mm_page_pcpu_drain") {
+
+                        $perprocesspid{$process_pid}->{HIGH_PCPU_DRAINS}++;
+                        $perprocesspid{$process_pid}->{STATE_PCPU_PAGES_DRAINED} = 0;
+                }
+
+                # Catch a full pcpu refill event
+                if ($perprocesspid{$process_pid}->{STATE_PCPU_PAGES_REFILLED} &&
+                                $tracepoint ne "mm_page_alloc_zone_locked") {
+                        $perprocesspid{$process_pid}->{HIGH_PCPU_REFILLS}++;
+                        $perprocesspid{$process_pid}->{STATE_PCPU_PAGES_REFILLED} = 0;
+                }
+
+                if ($sigint_pending) {
+                        last EVENT_PROCESS;
+                }
+        }
+}
+
+sub dump_stats {
+        my $hashref = shift;
+        my %stats = %$hashref;
+
+        # Dump per-process stats
+        my $process_pid;
+        my $max_strlen = 0;
+
+        # Get the maximum process name
+        foreach $process_pid (keys %perprocesspid) {
+                my $len = length($process_pid);
+                if ($len > $max_strlen) {
+                        $max_strlen = $len;
+                }
+        }
+        $max_strlen += 2;
+
+        printf("\n");
+        printf("%-" . $max_strlen . "s %8s %10s   %8s %8s   %8s %8s %8s   %8s %8s %8s %8s %8s %8s\n",
+                "Process", "Pages",  "Pages",      "Pages", "Pages", "PCPU",  "PCPU",   "PCPU",    "Fragment",  "Fragment", "MigType", "Fragment", "Fragment", "Unknown");
+        printf("%-" . $max_strlen . "s %8s %10s   %8s %8s   %8s %8s %8s   %8s %8s %8s %8s %8s %8s\n",
+                "details", "allocd", "allocd",     "freed", "freed", "pages", "drains", "refills", "Fallback", "Causing",   "Changed", "Severe", "Moderate", "");
+
+        printf("%-" . $max_strlen . "s %8s %10s   %8s %8s   %8s %8s %8s   %8s %8s %8s %8s %8s %8s\n",
+                "",        "",       "under lock", "direct", "pagevec", "drain", "", "", "", "", "", "", "", "");
+
+        foreach $process_pid (keys %stats) {
+                # Dump final aggregates
+                if ($stats{$process_pid}->{STATE_PCPU_PAGES_DRAINED}) {
+                        $stats{$process_pid}->{HIGH_PCPU_DRAINS}++;
+                        $stats{$process_pid}->{STATE_PCPU_PAGES_DRAINED} = 0;
+                }
+                if ($stats{$process_pid}->{STATE_PCPU_PAGES_REFILLED}) {
+                        $stats{$process_pid}->{HIGH_PCPU_REFILLS}++;
+                        $stats{$process_pid}->{STATE_PCPU_PAGES_REFILLED} = 0;
+                }
+
+                printf("%-" . $max_strlen . "s %8d %10d   %8d %8d   %8d %8d %8d   %8d %8d %8d %8d %8d %8d\n",
+                        $process_pid,
+                        $stats{$process_pid}->{MM_PAGE_ALLOC},
+                        $stats{$process_pid}->{MM_PAGE_ALLOC_ZONE_LOCKED},
+                        $stats{$process_pid}->{MM_PAGE_FREE_DIRECT},
+                        $stats{$process_pid}->{MM_PAGEVEC_FREE},
+                        $stats{$process_pid}->{MM_PAGE_PCPU_DRAIN},
+                        $stats{$process_pid}->{HIGH_PCPU_DRAINS},
+                        $stats{$process_pid}->{HIGH_PCPU_REFILLS},
+                        $stats{$process_pid}->{MM_PAGE_ALLOC_EXTFRAG},
+                        $stats{$process_pid}->{HIGH_EXT_FRAG},
+                        $stats{$process_pid}->{HIGH_EXT_FRAGMENT_CHANGED},
+                        $stats{$process_pid}->{HIGH_EXT_FRAGMENT_SEVERE},
+                        $stats{$process_pid}->{HIGH_EXT_FRAGMENT_MODERATE},
+                        $stats{$process_pid}->{EVENT_UNKNOWN});
+        }
+}
+
+sub aggregate_perprocesspid() {
+        my $process_pid;
+        my $process;
+        undef %perprocess;
+
+        foreach $process_pid (keys %perprocesspid) {
+                $process = $process_pid;
+                $process =~ s/-([0-9])*$//;
+                if ($process eq '') {
+                        $process = "NO_PROCESS_NAME";
+                }
+
+                $perprocess{$process}->{MM_PAGE_ALLOC} += $perprocesspid{$process_pid}->{MM_PAGE_ALLOC};
+                $perprocess{$process}->{MM_PAGE_ALLOC_ZONE_LOCKED} += $perprocesspid{$process_pid}->{MM_PAGE_ALLOC_ZONE_LOCKED};
+                $perprocess{$process}->{MM_PAGE_FREE_DIRECT} += $perprocesspid{$process_pid}->{MM_PAGE_FREE_DIRECT};
+                $perprocess{$process}->{MM_PAGEVEC_FREE} += $perprocesspid{$process_pid}->{MM_PAGEVEC_FREE};
+                $perprocess{$process}->{MM_PAGE_PCPU_DRAIN} += $perprocesspid{$process_pid}->{MM_PAGE_PCPU_DRAIN};
+                $perprocess{$process}->{HIGH_PCPU_DRAINS} += $perprocesspid{$process_pid}->{HIGH_PCPU_DRAINS};
+                $perprocess{$process}->{HIGH_PCPU_REFILLS} += $perprocesspid{$process_pid}->{HIGH_PCPU_REFILLS};
+                $perprocess{$process}->{MM_PAGE_ALLOC_EXTFRAG} += $perprocesspid{$process_pid}->{MM_PAGE_ALLOC_EXTFRAG};
+                $perprocess{$process}->{HIGH_EXT_FRAG} += $perprocesspid{$process_pid}->{HIGH_EXT_FRAG};
+                $perprocess{$process}->{HIGH_EXT_FRAGMENT_CHANGED} += $perprocesspid{$process_pid}->{HIGH_EXT_FRAGMENT_CHANGED};
+                $perprocess{$process}->{HIGH_EXT_FRAGMENT_SEVERE} += $perprocesspid{$process_pid}->{HIGH_EXT_FRAGMENT_SEVERE};
+                $perprocess{$process}->{HIGH_EXT_FRAGMENT_MODERATE} += $perprocesspid{$process_pid}->{HIGH_EXT_FRAGMENT_MODERATE};
+                $perprocess{$process}->{EVENT_UNKNOWN} += $perprocesspid{$process_pid}->{EVENT_UNKNOWN};
+        }
+}
+
+sub report() {
+        if (!$opt_ignorepid) {
+                dump_stats(\%perprocesspid);
+        } else {
+                aggregate_perprocesspid();
+                dump_stats(\%perprocess);
+        }
+}
+
+# Process events or signals until neither is available
+sub signal_loop() {
+        my $sigint_processed;
+        do {
+                $sigint_processed = 0;
+                process_events();
+
+                # Handle pending signals if any
+                if ($sigint_pending) {
+                        my $current_time = time;
+
+                        if ($sigint_exit) {
+                                print "Received exit signal\n";
+                                $sigint_pending = 0;
+                        }
+                        if ($sigint_report) {
+                                if ($current_time >= $sigint_received + 2) {
+                                        report();
+                                        $sigint_report = 0;
+                                        $sigint_pending = 0;
+                                        $sigint_processed = 1;
+                                }
+                        }
+                }
+        } while ($sigint_pending || $sigint_processed);
+}
+
+signal_loop();
+report();
diff --git a/Documentation/trace/power.txt b/Documentation/trace/power.txt
deleted file mode 100644
index cd805e16dc27..000000000000
--- a/Documentation/trace/power.txt
+++ /dev/null
@@ -1,17 +0,0 @@
-The power tracer collects detailed information about C-state and P-state
-transitions, instead of just looking at the high-level "average"
-information.
-
-There is a helper script found in scrips/tracing/power.pl in the kernel
-sources which can be used to parse this information and create a
-Scalable Vector Graphics (SVG) picture from the trace data.
-
-To use this tracer:
-
-        echo 0 > /sys/kernel/debug/tracing/tracing_enabled
-        echo power > /sys/kernel/debug/tracing/current_tracer
-        echo 1 > /sys/kernel/debug/tracing/tracing_enabled
-        sleep 1
-        echo 0 > /sys/kernel/debug/tracing/tracing_enabled
-        cat /sys/kernel/debug/tracing/trace | \
-                perl scripts/tracing/power.pl > out.sv
diff --git a/Documentation/trace/tracepoint-analysis.txt b/Documentation/trace/tracepoint-analysis.txt
new file mode 100644
index 000000000000..5eb4e487e667
--- /dev/null
+++ b/Documentation/trace/tracepoint-analysis.txt
@@ -0,0 +1,327 @@
+                Notes on Analysing Behaviour Using Events and Tracepoints
+
+                        Documentation written by Mel Gorman
+                PCL information heavily based on email from Ingo Molnar
+
+1. Introduction
+===============
+
+Tracepoints (see Documentation/trace/tracepoints.txt) can be used without
+creating custom kernel modules to register probe functions using the event
+tracing infrastructure.
+
+Simplistically, tracepoints will represent an important event that when can
+be taken in conjunction with other tracepoints to build a "Big Picture" of
+what is going on within the system. There are a large number of methods for
+gathering and interpreting these events. Lacking any current Best Practises,
+this document describes some of the methods that can be used.
+
+This document assumes that debugfs is mounted on /sys/kernel/debug and that
+the appropriate tracing options have been configured into the kernel. It is
+assumed that the PCL tool tools/perf has been installed and is in your path.
+
+2. Listing Available Events
+===========================
+
+2.1 Standard Utilities
+----------------------
+
+All possible events are visible from /sys/kernel/debug/tracing/events. Simply
+calling
+
+  $ find /sys/kernel/debug/tracing/events -type d
+
+will give a fair indication of the number of events available.
+
+2.2 PCL
+-------
+
+Discovery and enumeration of all counters and events, including tracepoints
+are available with the perf tool. Getting a list of available events is a
+simple case of
+
+  $ perf list 2>&1 | grep Tracepoint
+  ext4:ext4_free_inode                     [Tracepoint event]
+  ext4:ext4_request_inode                  [Tracepoint event]
+  ext4:ext4_allocate_inode                 [Tracepoint event]
+  ext4:ext4_write_begin                    [Tracepoint event]
+  ext4:ext4_ordered_write_end              [Tracepoint event]
+  [ .... remaining output snipped .... ]
+
+
+2. Enabling Events
+==================
+
+2.1 System-Wide Event Enabling
+------------------------------
+
+See Documentation/trace/events.txt for a proper description on how events
+can be enabled system-wide. A short example of enabling all events related
+to page allocation would look something like
+
+  $ for i in `find /sys/kernel/debug/tracing/events -name "enable" | grep mm_`; do echo 1 > $i; done
+
+2.2 System-Wide Event Enabling with SystemTap
+---------------------------------------------
+
+In SystemTap, tracepoints are accessible using the kernel.trace() function
+call. The following is an example that reports every 5 seconds what processes
+were allocating the pages.
+
+  global page_allocs
+
+  probe kernel.trace("mm_page_alloc") {
+        page_allocs[execname()]++
+  }
+
+  function print_count() {
+        printf ("%-25s %-s\n", "#Pages Allocated", "Process Name")
+        foreach (proc in page_allocs-)
+                printf("%-25d %s\n", page_allocs[proc], proc)
+        printf ("\n")
+        delete page_allocs
+  }
+
+  probe timer.s(5) {
+          print_count()
+  }
+
+2.3 System-Wide Event Enabling with PCL
+---------------------------------------
+
+By specifying the -a switch and analysing sleep, the system-wide events
+for a duration of time can be examined.
+
+ $ perf stat -a \
+        -e kmem:mm_page_alloc -e kmem:mm_page_free_direct \
+        -e kmem:mm_pagevec_free \
+        sleep 10
+ Performance counter stats for 'sleep 10':
+
+           9630  kmem:mm_page_alloc
+           2143  kmem:mm_page_free_direct
+           7424  kmem:mm_pagevec_free
+
+   10.002577764  seconds time elapsed
+
+Similarly, one could execute a shell and exit it as desired to get a report
+at that point.
+
+2.4 Local Event Enabling
+------------------------
+
+Documentation/trace/ftrace.txt describes how to enable events on a per-thread
+basis using set_ftrace_pid.
+
+2.5 Local Event Enablement with PCL
+-----------------------------------
+
+Events can be activate and tracked for the duration of a process on a local
+basis using PCL such as follows.
+
+  $ perf stat -e kmem:mm_page_alloc -e kmem:mm_page_free_direct \
+                 -e kmem:mm_pagevec_free ./hackbench 10
+  Time: 0.909
+
+    Performance counter stats for './hackbench 10':
+
+          17803  kmem:mm_page_alloc
+          12398  kmem:mm_page_free_direct
+           4827  kmem:mm_pagevec_free
+
+    0.973913387  seconds time elapsed
+
+3. Event Filtering
+==================
+
+Documentation/trace/ftrace.txt covers in-depth how to filter events in
+ftrace.  Obviously using grep and awk of trace_pipe is an option as well
+as any script reading trace_pipe.
+
+4. Analysing Event Variances with PCL
+=====================================
+
+Any workload can exhibit variances between runs and it can be important
+to know what the standard deviation in. By and large, this is left to the
+performance analyst to do it by hand. In the event that the discrete event
+occurrences are useful to the performance analyst, then perf can be used.
+
+  $ perf stat --repeat 5 -e kmem:mm_page_alloc -e kmem:mm_page_free_direct
+                        -e kmem:mm_pagevec_free ./hackbench 10
+  Time: 0.890
+  Time: 0.895
+  Time: 0.915
+  Time: 1.001
+  Time: 0.899
+
+   Performance counter stats for './hackbench 10' (5 runs):
+
+          16630  kmem:mm_page_alloc         ( +-   3.542% )
+          11486  kmem:mm_page_free_direct   ( +-   4.771% )
+           4730  kmem:mm_pagevec_free       ( +-   2.325% )
+
+    0.982653002  seconds time elapsed   ( +-   1.448% )
+
+In the event that some higher-level event is required that depends on some
+aggregation of discrete events, then a script would need to be developed.
+
+Using --repeat, it is also possible to view how events are fluctuating over
+time on a system wide basis using -a and sleep.
+
+  $ perf stat -e kmem:mm_page_alloc -e kmem:mm_page_free_direct \
+                -e kmem:mm_pagevec_free \
+                -a --repeat 10 \
+                sleep 1
+  Performance counter stats for 'sleep 1' (10 runs):
+
+           1066  kmem:mm_page_alloc         ( +-  26.148% )
+            182  kmem:mm_page_free_direct   ( +-   5.464% )
+            890  kmem:mm_pagevec_free       ( +-  30.079% )
+
+    1.002251757  seconds time elapsed   ( +-   0.005% )
+
+5. Higher-Level Analysis with Helper Scripts
+============================================
+
+When events are enabled the events that are triggering can be read from
+/sys/kernel/debug/tracing/trace_pipe in human-readable format although binary
+options exist as well. By post-processing the output, further information can
+be gathered on-line as appropriate. Examples of post-processing might include
+
+  o Reading information from /proc for the PID that triggered the event
+  o Deriving a higher-level event from a series of lower-level events.
+  o Calculate latencies between two events
+
+Documentation/trace/postprocess/trace-pagealloc-postprocess.pl is an example
+script that can read trace_pipe from STDIN or a copy of a trace. When used
+on-line, it can be interrupted once to generate a report without existing
+and twice to exit.
+
+Simplistically, the script just reads STDIN and counts up events but it
+also can do more such as
+
+  o Derive high-level events from many low-level events. If a number of pages
+    are freed to the main allocator from the per-CPU lists, it recognises
+    that as one per-CPU drain even though there is no specific tracepoint
+    for that event
+  o It can aggregate based on PID or individual process number
+  o In the event memory is getting externally fragmented, it reports
+    on whether the fragmentation event was severe or moderate.
+  o When receiving an event about a PID, it can record who the parent was so
+    that if large numbers of events are coming from very short-lived
+    processes, the parent process responsible for creating all the helpers
+    can be identified
+
+6. Lower-Level Analysis with PCL
+================================
+
+There may also be a requirement to identify what functions with a program
+were generating events within the kernel. To begin this sort of analysis, the
+data must be recorded. At the time of writing, this required root
+
+  $ perf record -c 1 \
+        -e kmem:mm_page_alloc -e kmem:mm_page_free_direct \
+        -e kmem:mm_pagevec_free \
+        ./hackbench 10
+  Time: 0.894
+  [ perf record: Captured and wrote 0.733 MB perf.data (~32010 samples) ]
+
+Note the use of '-c 1' to set the event period to sample. The default sample
+period is quite high to minimise overhead but the information collected can be
+very coarse as a result.
+
+This record outputted a file called perf.data which can be analysed using
+perf report.
+
+  $ perf report
+  # Samples: 30922
+  #
+  # Overhead    Command                     Shared Object
+  # ........  .........  ................................
+  #
+      87.27%  hackbench  [vdso]
+       6.85%  hackbench  /lib/i686/cmov/libc-2.9.so
+       2.62%  hackbench  /lib/ld-2.9.so
+       1.52%       perf  [vdso]
+       1.22%  hackbench  ./hackbench
+       0.48%  hackbench  [kernel]
+       0.02%       perf  /lib/i686/cmov/libc-2.9.so
+       0.01%       perf  /usr/bin/perf
+       0.01%       perf  /lib/ld-2.9.so
+       0.00%  hackbench  /lib/i686/cmov/libpthread-2.9.so
+  #
+  # (For more details, try: perf report --sort comm,dso,symbol)
+  #
+
+According to this, the vast majority of events occured triggered on events
+within the VDSO. With simple binaries, this will often be the case so lets
+take a slightly different example. In the course of writing this, it was
+noticed that X was generating an insane amount of page allocations so lets look
+at it
+
+  $ perf record -c 1 -f \
+                -e kmem:mm_page_alloc -e kmem:mm_page_free_direct \
+                -e kmem:mm_pagevec_free \
+                -p `pidof X`
+
+This was interrupted after a few seconds and
+
+  $ perf report
+  # Samples: 27666
+  #
+  # Overhead  Command                            Shared Object
+  # ........  .......  .......................................
+  #
+      51.95%     Xorg  [vdso]
+      47.95%     Xorg  /opt/gfx-test/lib/libpixman-1.so.0.13.1
+       0.09%     Xorg  /lib/i686/cmov/libc-2.9.so
+       0.01%     Xorg  [kernel]
+  #
+  # (For more details, try: perf report --sort comm,dso,symbol)
+  #
+
+So, almost half of the events are occuring in a library. To get an idea which
+symbol.
+
+  $ perf report --sort comm,dso,symbol
+  # Samples: 27666
+  #
+  # Overhead  Command                            Shared Object  Symbol
+  # ........  .......  .......................................  ......
+  #
+      51.95%     Xorg  [vdso]                                   [.] 0x000000ffffe424
+      47.93%     Xorg  /opt/gfx-test/lib/libpixman-1.so.0.13.1  [.] pixmanFillsse2
+       0.09%     Xorg  /lib/i686/cmov/libc-2.9.so               [.] _int_malloc
+       0.01%     Xorg  /opt/gfx-test/lib/libpixman-1.so.0.13.1  [.] pixman_region32_copy_f
+       0.01%     Xorg  [kernel]                                 [k] read_hpet
+       0.01%     Xorg  /opt/gfx-test/lib/libpixman-1.so.0.13.1  [.] get_fast_path
+       0.00%     Xorg  [kernel]                                 [k] ftrace_trace_userstack
+
+To see where within the function pixmanFillsse2 things are going wrong
+
+  $ perf annotate pixmanFillsse2
+  [ ... ]
+    0.00 :         34eeb:       0f 18 08                prefetcht0 (%eax)
+         :      }
+         :
+         :      extern __inline void __attribute__((__gnu_inline__, __always_inline__, _
+         :      _mm_store_si128 (__m128i *__P, __m128i __B) :      {
+         :        *__P = __B;
+   12.40 :         34eee:       66 0f 7f 80 40 ff ff    movdqa %xmm0,-0xc0(%eax)
+    0.00 :         34ef5:       ff
+   12.40 :         34ef6:       66 0f 7f 80 50 ff ff    movdqa %xmm0,-0xb0(%eax)
+    0.00 :         34efd:       ff
+   12.39 :         34efe:       66 0f 7f 80 60 ff ff    movdqa %xmm0,-0xa0(%eax)
+    0.00 :         34f05:       ff
+   12.67 :         34f06:       66 0f 7f 80 70 ff ff    movdqa %xmm0,-0x90(%eax)
+    0.00 :         34f0d:       ff
+   12.58 :         34f0e:       66 0f 7f 40 80          movdqa %xmm0,-0x80(%eax)
+   12.31 :         34f13:       66 0f 7f 40 90          movdqa %xmm0,-0x70(%eax)
+   12.40 :         34f18:       66 0f 7f 40 a0          movdqa %xmm0,-0x60(%eax)
+   12.31 :         34f1d:       66 0f 7f 40 b0          movdqa %xmm0,-0x50(%eax)
+
+At a glance, it looks like the time is being spent copying pixmaps to
+the card.  Further investigation would be needed to determine why pixmaps
+are being copied around so much but a starting point would be to take an
+ancient build of libpixmap out of the library path where it was totally
+forgotten about from months ago!