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

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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>
This commit is contained in:
Frederic Weisbecker 2009-07-01 21:02:09 +02:00 committed by Ingo Molnar
parent 5da5025858
commit 0406ca6d8e
4 changed files with 30 additions and 8 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
arch/x86/include/asm/stacktrace.h
View file

@ -3,6 +3,8 @@
extern int kstack_depth_to_print;
int x86_is_stack_id(int id, char *name);
/* Generic stack tracer with callbacks */
struct stacktrace_ops {

8
arch/x86/kernel/cpu/perf_counter.c
View file

@ -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);
}

6
arch/x86/kernel/dumpstack_32.c
View file

@ -19,6 +19,12 @@
#include "dumpstack.h"
/* Just a stub for now */
int x86_is_stack_id(int id, char *name)
{
return 0;
}
void dump_trace(struct task_struct *task, struct pt_regs *regs,
unsigned long *stack, unsigned long bp,
const struct stacktrace_ops *ops, void *data)

22
arch/x86/kernel/dumpstack_64.c
View file

@ -19,10 +19,8 @@
#include "dumpstack.h"
static unsigned long *in_exception_stack(unsigned cpu, unsigned long stack,
unsigned *usedp, char **idp)
{
static char ids[][8] = {
static char x86_stack_ids[][8] = {
[DEBUG_STACK - 1] = "#DB",
[NMI_STACK - 1] = "NMI",
[DOUBLEFAULT_STACK - 1] = "#DF",
@ -33,6 +31,15 @@ static unsigned long *in_exception_stack(unsigned cpu, unsigned long stack,
N_EXCEPTION_STACKS + DEBUG_STKSZ / EXCEPTION_STKSZ - 2] = "#DB[?]"
#endif
};
int x86_is_stack_id(int id, char *name)
{
return x86_stack_ids[id - 1] == name;
}
static unsigned long *in_exception_stack(unsigned cpu, unsigned long stack,
unsigned *usedp, char **idp)
{
unsigned k;
/*
@ -61,7 +68,7 @@ static unsigned long *in_exception_stack(unsigned cpu, unsigned long stack,
if (*usedp & (1U << k))
break;
*usedp |= 1U << k;
*idp = ids[k];
*idp = x86_stack_ids[k];
return (unsigned long *)end;
}
/*
@ -81,12 +88,13 @@ static unsigned long *in_exception_stack(unsigned cpu, unsigned long stack,
do {
++j;
end -= EXCEPTION_STKSZ;
ids[j][4] = '1' + (j - N_EXCEPTION_STACKS);
x86_stack_ids[j][4] = '1' +
(j - N_EXCEPTION_STACKS);
} while (stack < end - EXCEPTION_STKSZ);
if (*usedp & (1U << j))
break;
*usedp |= 1U << j;
*idp = ids[j];
*idp = x86_stack_ids[j];
return (unsigned long *)end;
}
#endif