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* markers: fix sparse integer as NULL pointer warningHarvey Harrison2008-07-25
| | | | | | | | | kernel/trace/trace_sysprof.c:164:20: warning: Using plain integer as NULL pointer Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* cpumask: Replace cpumask_of_cpu with cpumask_of_cpu_ptrMike Travis2008-07-18
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | * This patch replaces the dangerous lvalue version of cpumask_of_cpu with new cpumask_of_cpu_ptr macros. These are patterned after the node_to_cpumask_ptr macros. In general terms, if there is a cpumask_of_cpu_map[] then a pointer to the cpumask_of_cpu_map[cpu] entry is used. The cpumask_of_cpu_map is provided when there is a large NR_CPUS count, reducing greatly the amount of code generated and stack space used for cpumask_of_cpu(). The pointer to the cpumask_t value is needed for calling set_cpus_allowed_ptr() to reduce the amount of stack space needed to pass the cpumask_t value. If there isn't a cpumask_of_cpu_map[], then a temporary variable is declared and filled in with value from cpumask_of_cpu(cpu) as well as a pointer variable pointing to this temporary variable. Afterwards, the pointer is used to reference the cpumask value. The compiler will optimize out the extra dereference through the pointer as well as the stack space used for the pointer, resulting in identical code. A good example of the orthogonal usages is in net/sunrpc/svc.c: case SVC_POOL_PERCPU: { unsigned int cpu = m->pool_to[pidx]; cpumask_of_cpu_ptr(cpumask, cpu); *oldmask = current->cpus_allowed; set_cpus_allowed_ptr(current, cpumask); return 1; } case SVC_POOL_PERNODE: { unsigned int node = m->pool_to[pidx]; node_to_cpumask_ptr(nodecpumask, node); *oldmask = current->cpus_allowed; set_cpus_allowed_ptr(current, nodecpumask); return 1; } Signed-off-by: Mike Travis <travis@sgi.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* Merge branch 'tracing/ftrace' into auto-ftrace-nextIngo Molnar2008-07-14
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| * ftrace: build fix for ftraced_suspendIngo Molnar2008-07-11
| | | | | | | | | | | | | | | | | | | | fix: kernel/trace/ftrace.c:1615: error: 'ftraced_suspend' undeclared (first use in this function) kernel/trace/ftrace.c:1615: error: (Each undeclared identifier is reported only once kernel/trace/ftrace.c:1615: error: for each function it appears in.) Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * ftrace: separate out the function enabled variableSteven Rostedt2008-07-11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently the function tracer uses the global tracer_enabled variable that is used to keep track if the tracer is enabled or not. The function tracing startup needs to be separated out, otherwise the internal happenings of the tracer startup is also recorded. This patch creates a ftrace_function_enabled variable to all the starting of the function traces to happen after everything has been started. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Cc: Steven Rostedt <srostedt@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * ftrace: add ftrace_kill_atomicSteven Rostedt2008-07-11
| | | | | | | | | | | | | | | | | | | | | | | | | | It has been suggested that I add a way to disable the function tracer on an oops. This code adds a ftrace_kill_atomic. It is not meant to be used in normal situations. It will disable the ftrace tracer, but will not perform the nice shutdown that requires scheduling. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Cc: Steven Rostedt <srostedt@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * ftrace: use current CPU for function startupSteven Rostedt2008-07-11
| | | | | | | | | | | | | | | | | | | | | | | | | | This is more of a clean up. Currently the function tracer initializes the tracer with which ever CPU was last used for tracing. This value isn't realy useful for function tracing, but at least it should be something other than a random number. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Cc: Steven Rostedt <srostedt@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * ftrace: start wakeup tracing after setting function tracerSteven Rostedt2008-07-11
| | | | | | | | | | | | | | | | | | | | | | Enabling the wakeup tracer before enabling the function tracing causes some strange results due to the dynamic enabling of the functions. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Cc: Steven Rostedt <srostedt@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * ftrace: check proper config for preempt typeSteven Rostedt2008-07-11
| | | | | | | | | | | | | | | | | | | | There is no CONFIG_PREEMPT_DESKTOP. Use the proper entry CONFIG_PREEMPT. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Cc: Steven Rostedt <srostedt@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * ftrace: define function trace nopSteven Rostedt2008-07-11
| | | | | | | | | | | | | | | | | | | | | | When CONFIG_FTRACE is not enabled, the tracing_start_functon_trace and tracing_stop_function_trace should be nops. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Cc: Steven Rostedt <srostedt@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * ftrace: move sched_switch enable after markersSteven Rostedt2008-07-11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | We have two markers now that are enabled on sched_switch. One that records the context switching and the other that records task wake ups. Currently we enable the tracing first and then set the markers. This causes some confusing traces: # tracer: sched_switch # # TASK-PID CPU# TIMESTAMP FUNCTION # | | | | | trace-cmd-3973 [00] 115.834817: 3973:120:R + 3: 0:S trace-cmd-3973 [01] 115.834910: 3973:120:R + 6: 0:S trace-cmd-3973 [02] 115.834910: 3973:120:R + 9: 0:S trace-cmd-3973 [03] 115.834910: 3973:120:R + 12: 0:S trace-cmd-3973 [02] 115.834910: 3973:120:R + 9: 0:S <idle>-0 [02] 115.834910: 0:140:R ==> 3973:120:R Here we see that trace-cmd with PID 3973 wakes up task 9 but the next line shows the idle task doing a context switch to task 3973. Enabling the tracing to _after_ the markers are set creates a much saner output: # tracer: sched_switch # # TASK-PID CPU# TIMESTAMP FUNCTION # | | | | | <idle>-0 [02] 7922.634225: 0:140:R ==> 4790:120:R trace-cmd-4789 [03] 7922.634225: 0:140:R + 4790:120:R Signed-off-by: Steven Rostedt <srostedt@redhat.com> Cc: Steven Rostedt <srostedt@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | Merge branch 'tracing/sysprof' into auto-ftrace-nextIngo Molnar2008-07-10
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| * | sysprof: make it depend on X86Thomas Gleixner2008-05-24
| | | | | | | | | | | | Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * | ftrace/sysprof: don't trace the user stack if we are a kernel thread.Soeren Sandmann2008-05-23
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Check that current->mm is non-NULL before attempting to trace the user stack. Also take depth of the kernel stack into account when comparing against sample_max_depth. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * | sysprof: update copyrightsIngo Molnar2008-05-23
| | | | | | | | | | | | | | | Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * | sysprof: kernel traceSoeren Sandmann Pedersen2008-05-23
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | add kernel backtracing to the sysprof tracer. change the format of the data, so that type=0 means beginning of stack trace, 1 means kernel address, 2 means user address, and 3 means end of trace. EIP addresses are no longer distinguished from return addresses, mostly because sysprof userspace doesn't make use of it. It may be worthwhile adding this back in though, just in case it becomes interesting. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * | ftrace: make it more available in the KconfigThomas Gleixner2008-05-23
| | | | | | | | | | | | Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * | ftrace: fix __trace_special()Thomas Gleixner2008-05-23
| | | | | | | | | | | | Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * | ftrace: remove notraceThomas Gleixner2008-05-23
| | | | | | | | | | | | | | | | | | Remove the notrace annotations. The build logic takes care of that. Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * | ftrace: sysprof updatesIngo Molnar2008-05-23
| | | | | | | | | | | | | | | | | | | | | make the sample period configurable. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * | ftrace: sysprof fixIngo Molnar2008-05-23
| | | | | | | | | | | | | | | Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * | ftrace: make sysprof dependent on x86 for nowIngo Molnar2008-05-23
| | | | | | | | | | | | | | | | | | | | | | | | that's the only tested platform for now. If there's interest we can make it generic easily. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * | ftrace: sysprof plugin improvementIngo Molnar2008-05-23
| | | | | | | | | | | | | | | | | | | | | add sample maximum depth. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * | ftrace: sysprof-plugin, add self-testsIngo Molnar2008-05-23
| | | | | | | | | | | | | | | Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * | ftrace: extend sysprof plugin some moreIngo Molnar2008-05-23
| | | | | | | | | | | | | | | Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * | ftrace: extend sysprof pluginIngo Molnar2008-05-23
| | | | | | | | | | | | | | | | | | | | | add per CPU hrtimers. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * | ftrace: add sysprof pluginIngo Molnar2008-05-23
| | | | | | | | | | | | | | | | | | | | | very first baby version. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* | | Merge branch 'tracing/mmiotrace' into auto-ftrace-nextIngo Molnar2008-07-10
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| * | x86 mmiotrace: use resource_size_t for phys addressesPekka Paalanen2008-05-24
| | | | | | | | | | | | | | | Signed-off-by: Pekka Paalanen <pq@iki.fi> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * | mmiotrace: do not print bogus pid for maps eitherPekka Paalanen2008-05-24
| | | | | | | | | | | | | | | Signed-off-by: Pekka Paalanen <pq@iki.fi> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * | mmiotrace: print overrun countsPekka Paalanen2008-05-24
| | | | | | | | | | | | | | | Signed-off-by: Pekka Paalanen <pq@iki.fi> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * | mmiotrace: print header using the read hook.Pekka Paalanen2008-05-24
| | | | | | | | | | | | | | | | | | | | | Now the header is printed only for `trace_pipe' file. Signed-off-by: Pekka Paalanen <pq@iki.fi> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * | x86 mmiotrace: Do not print bogus pidPekka Paalanen2008-05-24
| | | | | | | | | | | | | | | | | | | | | | | | | | | Non-zero pid indicates the MMIO access originated in user space. We do not catch that kind of accesses yet, so always print zero for now. Signed-off-by: Pekka Paalanen <pq@iki.fi> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * | mmiotrace: ftrace fixIngo Molnar2008-05-24
| | | | | | | | | | | | | | | Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * | ftrace: mmiotrace update, #2Pekka Paalanen2008-05-24
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | another weekend, another patch. This should apply on top of my previous patch from March 23rd. Summary of changes: - Print PCI device list in output header - work around recursive probe hits on SMP - refactor dis/arm_kmmio_fault_page() and add check for page levels - remove un/reference_kmmio(), the die notifier hook is registered permanently into the list - explicitly check for single stepping in die notifier callback I have tested this version on my UP Athlon64 desktop with Nouveau, and SMP Core 2 Duo laptop with the proprietary nvidia driver. Both systems are 64-bit. One previously unknown bug crept into daylight: the ftrace framework's output routines print the first entry last after buffer has wrapped around. The most important regressions compared to non-ftrace mmiotrace at this time are: - failure of trace_pipe file - illegal lines in output file - unaware of losing data due to buffer full Personally I'd like to see these three solved before submitting to mainline. Other issues may come up once we know when we lose events. Signed-off-by: Pekka Paalanen <pq@iki.fi> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * | ftrace: mmiotrace, updatesPekka Paalanen2008-05-24
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | here is a patch that makes mmiotrace work almost well within the tracing framework. The patch applies on top of my previous patch. I have my own output formatting in place now. Summary of changes: - fix the NULL dereference that was due to not calling tracing_reset() - add print_line() callback into struct tracer - implement print_line() for mmiotrace, producing up-to-spec text - add my output header, but that is not really called in the right place - rewrote the main structs in mmiotrace - added two new trace entry types: TRACE_MMIO_RW and TRACE_MMIO_MAP - made some functions in trace.c non-static - check current==NULL in tracing_generic_entry_update() - fix(?) comparison in trace_seq_printf() Things seem to work fine except a few issues. Markers (text lines injected into mmiotrace log) are missing, I did not feel hacking them in before we have variable length entries. My output header is printed only for 'trace' file, but not 'trace_pipe'. For some reason, despite my quick fix, iter->trace is NULL in print_trace_line() when called from 'trace_pipe' file, which means I don't get proper output formatting. I only tried by loading nouveau.ko, which just detects the card, and that is traced fine. I didn't try further. Map, two reads and unmap. Works perfectly. I am missing the information about overflows, I'd prefer to have a counter for lost events. I didn't try, but I guess currently there is no way of knowning when it overflows? So, not too far from being fully operational, it seems :-) And looking at the diffstat, there also is some 700-900 lines of user space code that just became obsolete. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * | ftrace: add mmiotrace pluginPekka Paalanen2008-05-24
| |/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | On Sat, 22 Mar 2008 13:07:47 +0100 Ingo Molnar <mingo@elte.hu> wrote: > > > i'd suggest the following: pull x86.git and sched-devel.git into a > > > single tree [the two will combine without rejects]. Then try to add a > > > kernel/tracing/trace_mmiotrace.c ftrace plugin. The trace_sysprof.c > > > plugin might be a good example. > > > > I did this and now I have mmiotrace enabled/disabled via the tracing > > framework (what do we call this, since ftrace is one of the tracers?). > > cool! could you send the patches for that? (even if they are not fully > functional yet) Patch attached in the end. Nice to see how much code disappeared. I tried to mark all the features I had to break with XXX-comments. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* | ftrace: prevent ftrace modifications while being kprobe'd, v2Abhishek Sagar2008-07-03
| | | | | | | | | | | | | | | | add two missing chunks for ftrace+kprobe. Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | ftrace: avoid modifying kprobe'd recordsAbhishek Sagar2008-06-23
| | | | | | | | | | | | | | | | | | | | | | Avoid modifying the mcount call-site if there is a kprobe installed on it. These records are not marked as failed however. This allowed the filter rules on them to remain up-to-date. Whenever the kprobe on the corresponding record is removed, the record gets updated as normal. Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | ftrace: freeze kprobe'd recordsAbhishek Sagar2008-06-23
| | | | | | | | | | | | | | | | | | | | | | | | | | | | Let records identified as being kprobe'd be marked as "frozen". The trouble with records which have a kprobe installed on their mcount call-site is that they don't get updated. So if such a function which is currently being traced gets its tracing disabled due to a new filter rule (or because it was added to the notrace list) then it won't be updated and continue being traced. This patch allows scanning of all frozen records during tracing to check if they should be traced. Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | ftrace: store mcount address in rec->ipAbhishek Sagar2008-06-23
| | | | | | | | | | | | | | | | | | | | | | | | Record the address of the mcount call-site. Currently all archs except sparc64 record the address of the instruction following the mcount call-site. Some general cleanups are entailed. Storing mcount addresses in rec->ip enables looking them up in the kprobe hash table later on to check if they're kprobe'd. Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com> Cc: davem@davemloft.net Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | namespacecheck: fixesIngo Molnar2008-06-16
| | | | | | | | Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | ftrace: fix "notrace" filtering priorityAbhishek Sagar2008-06-14
| | | | | | | | | | | | | | | | | | | | | | | | | | This is a fix to give notrace filter rules priority over "set_ftrace_filter" rules. This fix ensures that functions which are set to be filtered and are concurrently marked as "notrace" don't get recorded. As of now, if a record is marked as FTRACE_FL_FILTER and is enabled, then the notrace flag is not checked. Tested on x86-32. Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | ftrace: fix printoutJiri Slaby2008-06-12
| | | | | | | | | | | | | | | | | | Do not print loglevel before "entries of %ld bytes". Move it to the previous pr_info. Signed-off-by: Jiri Slaby <jirislaby@gmail.com> Cc: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | ftrace: disable tracing when current_tracer is set to "none"Ankita Garg2008-06-10
| | | | | | | | | | | | | | | | | | | | | | | | Found that inspite of setting the current_tracer to "none", trace from the previous trace type continued to be collected. The patch below fixes this and causes the trace to be disabled when the "none" type is selected. Compile and boot tested the patch for functionality. Signed-off-by: Ankita Garg <ankita@in.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | ftrace: prevent freeing of all failed updatesAbhishek Sagar2008-06-10
| | | | | | | | | | | | | | | | | | | | Steven Rostedt wrote: > If we unload a module and reload it, will it ever get converted again? The intent was always to filter core kernel functions to prevent their freeing. Here's a fix which should allow re-recording of module call-sites. Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | ftrace: add debugfs entry 'failures'Abhishek Sagar2008-06-10
| | | | | | | | | | | | | | | | | | | | Identify functions which had their mcount call-site updates failed. This can help us track functions which ftrace shouldn't fiddle with, and are thus not being traced. If there is no race with any external agent which is modifying the mcount call-site, then this file displays no entries (normal case). Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | ftrace: remove ftrace_ip_converted()Abhishek Sagar2008-06-10
| | | | | | | | | | | | | | Remove the unneeded function ftrace_ip_converted(). Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | ftrace: prevent freeing of all failed updatesAbhishek Sagar2008-06-10
| | | | | | | | | | | | | | | | | | | | | | | | Prevent freeing of records which cause problems and correspond to function from core kernel text. A new flag, FTRACE_FL_CONVERTED is used to mark a record as "converted". All other records are patched lazily to NOPs. Failed records now also remain on frace_hash table. Each invocation of ftrace_record_ip now checks whether the traced function has ever been recorded (including past failures) and doesn't re-record it again. Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | ftrace: user update and disable dynamic ftrace daemonSteven Rostedt2008-06-02
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | In dynamic ftrace, the mcount function starts off pointing to a stub function that just returns. On start up, the call to the stub is modified to point to a "record_ip" function. The job of the record_ip function is to add the function to a pre-allocated hash list. If the function is already there, it simply is ignored, otherwise it is added to the list. Later, a ftraced daemon wakes up and calls kstop_machine if any functions have been recorded, and changes the calls to the recorded functions to a simple nop. If no functions were recorded, the daemon goes back to sleep. The daemon wakes up once a second to see if it needs to update any newly recorded functions into nops. Usually it does not, but if a lot of code has been executed for the first time in the kernel, the ftraced daemon will call kstop_machine to update those into nops. The problem currently is that there's no way to stop the daemon from doing this, and it can cause unneeded latencies (800us which for some is bothersome). This patch adds a new file /debugfs/tracing/ftraced_enabled. If the daemon is active, reading this will return "enabled\n" and "disabled\n" when the daemon is not running. To disable the daemon, the user can echo "0" or "disable" into this file, and "1" or "enable" to re-enable the daemon. Since the daemon is used to convert the functions into nops to increase the performance of the system, I also added that anytime something is written into the ftraced_enabled file, kstop_machine will run if there are new functions that have been detected that need to be converted. This way the user can disable the daemon but still be able to control the conversion of the mcount calls to nops by simply, "echo 0 > /debugfs/tracing/ftraced_enabled" when they need to do more conversions. To see the number of converted functions: "cat /debugfs/tracing/dyn_ftrace_total_info" Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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