perf_counter: Ignore the nmi call frames in the x86-64 backtraces

About every callchains recorded with perf record are filled up
including the internal perfcounter nmi frame:

 perf_callchain
 perf_counter_overflow
 intel_pmu_handle_irq
 perf_counter_nmi_handler
 notifier_call_chain
 atomic_notifier_call_chain
 notify_die
 do_nmi
 nmi

We want ignore this frame as it's not interesting for
instrumentation. To solve this, we simply ignore every frames
from nmi context.

New example of "perf report -s sym -c" after this patch:

9.59%  [k] search_by_key
             4.88%
                search_by_key
                reiserfs_read_locked_inode
                reiserfs_iget
                reiserfs_lookup
                do_lookup
                __link_path_walk
                path_walk
                do_path_lookup
                user_path_at
                vfs_fstatat
                vfs_lstat
                sys_newlstat
                system_call_fastpath
                __lxstat
                0x406fb1

             3.19%
                search_by_key
                search_by_entry_key
                reiserfs_find_entry
                reiserfs_lookup
                do_lookup
                __link_path_walk
                path_walk
                do_path_lookup
                user_path_at
                vfs_fstatat
                vfs_lstat
                sys_newlstat
                system_call_fastpath
                __lxstat
                0x406fb1
[...]

For now this patch only solves the problem in x86-64.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Anton Blanchard <anton@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <1246474930-6088-1-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 7 insertions, 1 deletions

diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c
index d4cf4ce19aac..36c3dc7b8991 100644
--- a/arch/x86/kernel/cpu/perf_counter.c
+++ b/arch/x86/kernel/cpu/perf_counter.c
@@ -1561,6 +1561,7 @@ void callchain_store(struct perf_callchain_entry *entry, u64 ip)
 
 static DEFINE_PER_CPU(struct perf_callchain_entry, irq_entry);
 static DEFINE_PER_CPU(struct perf_callchain_entry, nmi_entry);
+static DEFINE_PER_CPU(int, in_nmi_frame);
 
 
 static void
@@ -1576,7 +1577,9 @@ static void backtrace_warning(void *data, char *msg)
 
 static int backtrace_stack(void *data, char *name)
 {
-        /* Process all stacks: */
+        per_cpu(in_nmi_frame, smp_processor_id()) =
+                        x86_is_stack_id(NMI_STACK, name);
+
         return 0;
 }
 
@@ -1584,6 +1587,9 @@ static void backtrace_address(void *data, unsigned long addr, int reliable)
 {
         struct perf_callchain_entry *entry = data;
 
+        if (per_cpu(in_nmi_frame, smp_processor_id()))
+                return;
+
         if (reliable)
                 callchain_store(entry, addr);
 }