On Mon, Apr 04, 2016 at 09:52:47PM -0700, Alexei Starovoitov wrote: > 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_alloc
Its not actually allocated; but because its a static uninitialized variable we get .bss like behaviour and the initial value is copied to all CPUs when the per-cpu allocator thingy bootstraps SMP IIRC. > 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 Indeed. > move it into > perf_ftrace_function_call that calls it with stack allocated pt_regs. Hmm, is there a reason that's still on-stack instead of using the per-cpu thing, Steve? > Signed-off-by: Alexei Starovoitov <a...@kernel.org> In any case, Acked-by: Peter Zijlstra (Intel) <pet...@infradead.org>
