From f6d9dd237da400effb265f3554c64413f8a3e7b4 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 20 Nov 2009 22:19:48 +0100 Subject: [PATCH] perf: Optimize perf_event_mmap_ctx() 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: <20091120212508.606459548@chello.nl> Signed-off-by: Ingo Molnar --- kernel/perf_event.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-) diff --git a/kernel/perf_event.c b/kernel/perf_event.c index 4deefaace90e..68fbf4ff6888 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -3493,15 +3493,10 @@ static void perf_event_mmap_ctx(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_event_mmap_match(event, mmap_event)) perf_event_mmap_output(event, mmap_event); } - rcu_read_unlock(); } static void perf_event_mmap_event(struct perf_mmap_event *mmap_event) @@ -3557,11 +3552,11 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event) mmap_event->event_id.header.size = sizeof(mmap_event->event_id) + size; + rcu_read_lock(); cpuctx = &get_cpu_var(perf_cpu_context); perf_event_mmap_ctx(&cpuctx->ctx, mmap_event); put_cpu_var(perf_cpu_context); - rcu_read_lock(); /* * doesn't really matter which of the child contexts the * events ends up in. -- GitLab