Re: [PATCH] perf: Fix inconsistency between IP and callchainsampling
From: Frederic Weisbecker
Date: Thu Jan 21 2010 - 08:20:28 EST
On Mon, Jan 18, 2010 at 04:47:07PM +1100, Anton Blanchard wrote:
> 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.
> Signed-off-by: Anton Blanchard <anton@xxxxxxxxx>
I'm queuing it. Thanks.
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