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perf: optimize perf_fetch_caller_regs

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avoid memset in perf_fetch_caller_regs, since it's the critical path of all tracepoints.
It's called from perf_sw_event_sched, perf_event_task_sched_in and all of perf_trace_##call
with this_cpu_ptr(&__perf_regs[..]) which are zero initialized by perpcu init logic and
subsequent call to perf_arch_fetch_caller_regs initializes the same fields on all archs,
so we can safely drop memset from all of the above cases and move it into
perf_ftrace_function_call that calls it with stack allocated pt_regs.

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Alexei Starovoitov 2016-04-06 18:43:22 -07:00 committed by David S. Miller
parent b33b0a1bf6
commit ec5e099d6e
2 changed files with 1 additions and 2 deletions
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2
include/linux/perf_event.h
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@ -882,8 +882,6 @@ static inline void perf_arch_fetch_caller_regs(struct pt_regs *regs, unsigned lo
*/
static inline void perf_fetch_caller_regs(struct pt_regs *regs)
{
memset(regs, 0, sizeof(*regs));
perf_arch_fetch_caller_regs(regs, CALLER_ADDR0);
}

1
kernel/trace/trace_event_perf.c
View File

@ -316,6 +316,7 @@ perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip,
BUILD_BUG_ON(ENTRY_SIZE > PERF_MAX_TRACE_SIZE);
memset(&regs, 0, sizeof(regs));
perf_fetch_caller_regs(&regs);
entry = perf_trace_buf_prepare(ENTRY_SIZE, TRACE_FN, NULL, &rctx);