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authorAnton Blanchard <anton@samba.org>2010-01-18 16:47:07 +1100
committerFrederic Weisbecker <fweisbec@gmail.com>2010-01-28 14:31:20 +0100
commit339ce1a4dc2ca26444c4f65c31b71a5056f3bb0b (patch)
tree84b0f9eeb823d788a79d6d601a01c0433d956132 /arch
parent408f0d18ba6b9bb447f807f621b2c9663c5cf638 (diff)
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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>
Diffstat (limited to 'arch')
-rw-r--r--arch/powerpc/kernel/perf_callchain.c3
-rw-r--r--arch/sh/kernel/perf_callchain.c3
-rw-r--r--arch/x86/kernel/cpu/perf_event.c3
3 files changed, 0 insertions, 9 deletions
diff --git a/arch/powerpc/kernel/perf_callchain.c b/arch/powerpc/kernel/perf_callchain.c
index a3c11ca..95ad9da 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 24ea837..a9dd3ab 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 b1bb8c5..ed1998b 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;