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Commit ec5e099d authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by David S. Miller
Browse files

perf: optimize perf_fetch_caller_regs 



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: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent b33b0a1b

include/linux/perf_event.h

+0 −2
Original line number Diff line number Diff line
@@ -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);

}

kernel/trace/trace_event_perf.c

+1 −0
Original line number Diff line number Diff line
@@ -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);