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: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -882,8 +882,6 @@ static inline void perf_arch_fetch_caller_regs(struct pt_regs *regs, unsigned lo
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*/
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static inline void perf_fetch_caller_regs(struct pt_regs *regs)
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{
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memset(regs, 0, sizeof(*regs));
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perf_arch_fetch_caller_regs(regs, CALLER_ADDR0);
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}
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@ -316,6 +316,7 @@ perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip,
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BUILD_BUG_ON(ENTRY_SIZE > PERF_MAX_TRACE_SIZE);
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memset(®s, 0, sizeof(regs));
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perf_fetch_caller_regs(®s);
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entry = perf_trace_buf_prepare(ENTRY_SIZE, TRACE_FN, NULL, &rctx);
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