Commit-ID: f6d9dd237da400effb265f3554c64413f8a3e7b4 Gitweb: http://git.kernel.org/tip/f6d9dd237da400effb265f3554c64413f8a3e7b4 Author: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> AuthorDate: Fri, 20 Nov 2009 22:19:48 +0100 Committer: Ingo Molnar <mingo@xxxxxxx> CommitDate: Sat, 21 Nov 2009 14:11:37 +0100 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 <a.p.zijlstra@xxxxxxxxx> Cc: Paul Mackerras <paulus@xxxxxxxxx> LKML-Reference: <20091120212508.606459548@xxxxxxxxx> Signed-off-by: Ingo Molnar <mingo@xxxxxxx> --- kernel/perf_event.c | 7 +------ 1 files changed, 1 insertions(+), 6 deletions(-) diff --git a/kernel/perf_event.c b/kernel/perf_event.c index 4deefaa..68fbf4f 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 @@ got_name: 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. -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html