From: Peter Zijlstra Date: Fri, 20 Nov 2009 21:19:45 +0000 (+0100) Subject: perf: Optimize perf_swevent_ctx_event() X-Git-Tag: Ubuntu-snapdragon-4.4.0-1050.54~23863^2~137 X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=81520183878a8813c71c9372de28bb70913ba549;p=mirror_ubuntu-artful-kernel.git perf: Optimize perf_swevent_ctx_event() Remove a rcu_read_{,un}lock() pair and a few conditionals. We can remove the rcu_read_lock() by increasing the scope of one in the calling function. We can do away with the system_state check if the machine still boots after this patch (seems to be the case). We can do away with the list_empty() check because the bare list_for_each_entry_rcu() reduces to that now that we've removed everything else. Signed-off-by: Peter Zijlstra Cc: Paul Mackerras LKML-Reference: <20091120212508.378188589@chello.nl> Signed-off-by: Ingo Molnar --- diff --git a/kernel/perf_event.c b/kernel/perf_event.c index 8e55b440e28a..cda17acfcaf8 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -3886,15 +3886,10 @@ static void perf_swevent_ctx_event(struct perf_event_context *ctx, { struct perf_event *event; - if (system_state != SYSTEM_RUNNING || list_empty(&ctx->event_list)) - return; - - rcu_read_lock(); list_for_each_entry_rcu(event, &ctx->event_list, event_entry) { if (perf_swevent_match(event, type, event_id, data, regs)) perf_swevent_add(event, nr, nmi, data, regs); } - rcu_read_unlock(); } static int *perf_swevent_recursion_context(struct perf_cpu_context *cpuctx) @@ -3926,9 +3921,9 @@ static void do_perf_sw_event(enum perf_type_id type, u32 event_id, (*recursion)++; barrier(); + rcu_read_lock(); perf_swevent_ctx_event(&cpuctx->ctx, type, event_id, nr, nmi, data, regs); - rcu_read_lock(); /* * doesn't really matter which of the child contexts the * events ends up in.