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| author | Anton Blanchard <anton@samba.org> | 2010-01-18 16:47:07 +1100 |
|---|---|---|
| committer | Frederic Weisbecker <fweisbec@gmail.com> | 2010-01-28 14:31:20 +0100 |
| commit | 339ce1a4dc2ca26444c4f65c31b71a5056f3bb0b (patch) | |
| tree | 84b0f9eeb823d788a79d6d601a01c0433d956132 | |
| parent | 408f0d18ba6b9bb447f807f621b2c9663c5cf638 (diff) | |
| download | lwn-339ce1a4dc2ca26444c4f65c31b71a5056f3bb0b.tar.gz lwn-339ce1a4dc2ca26444c4f65c31b71a5056f3bb0b.zip | |
perf: Fix inconsistency between IP and callchain sampling
When running perf across all cpus with backtracing (-a -g), sometimes we
get samples without associated backtraces:
23.44% init [kernel] [k] restore
11.46% init eeba0c [k] 0x00000000eeba0c
6.77% swapper [kernel] [k] .perf_ctx_adjust_freq
5.73% init [kernel] [k] .__trace_hcall_entry
4.69% perf libc-2.9.so [.] 0x0000000006bb8c
|
|--11.11%-- 0xfffa941bbbc
It turns out the backtrace code has a check for the idle task and the IP
sampling does not. This creates problems when profiling an interrupt
heavy workload (in my case 10Gbit ethernet) since we get no backtraces
for interrupts received while idle (ie most of the workload).
Right now x86 and sh check that current is not NULL, which should never
happen so remove that too.
Idle task's exclusion must be performed from the core code, on top
of perf_event_attr:exclude_idle.
Signed-off-by: Anton Blanchard <anton@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mundt <lethal@linux-sh.org>
LKML-Reference: <20100118054707.GT12666@kryten>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
| -rw-r--r-- | arch/powerpc/kernel/perf_callchain.c | 3 | ||||
| -rw-r--r-- | arch/sh/kernel/perf_callchain.c | 3 | ||||
| -rw-r--r-- | arch/x86/kernel/cpu/perf_event.c | 3 |
3 files changed, 0 insertions, 9 deletions
diff --git a/arch/powerpc/kernel/perf_callchain.c b/arch/powerpc/kernel/perf_callchain.c index a3c11cac3d71..95ad9dad298e 100644 --- a/arch/powerpc/kernel/perf_callchain.c +++ b/arch/powerpc/kernel/perf_callchain.c @@ -495,9 +495,6 @@ struct perf_callchain_entry *perf_callchain(struct pt_regs *regs) entry->nr = 0; - if (current->pid == 0) /* idle task? */ - return entry; - if (!user_mode(regs)) { perf_callchain_kernel(regs, entry); if (current->mm) diff --git a/arch/sh/kernel/perf_callchain.c b/arch/sh/kernel/perf_callchain.c index 24ea837eac5b..a9dd3abde28e 100644 --- a/arch/sh/kernel/perf_callchain.c +++ b/arch/sh/kernel/perf_callchain.c @@ -68,9 +68,6 @@ perf_do_callchain(struct pt_regs *regs, struct perf_callchain_entry *entry) is_user = user_mode(regs); - if (!current || current->pid == 0) - return; - if (is_user && current->state != TASK_RUNNING) return; diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c index b1bb8c550526..ed1998b28a7c 100644 --- a/arch/x86/kernel/cpu/perf_event.c +++ b/arch/x86/kernel/cpu/perf_event.c @@ -2425,9 +2425,6 @@ perf_do_callchain(struct pt_regs *regs, struct perf_callchain_entry *entry) is_user = user_mode(regs); - if (!current || current->pid == 0) - return; - if (is_user && current->state != TASK_RUNNING) return; |