From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756288AbZKTVb5 (ORCPT ); Fri, 20 Nov 2009 16:31:57 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756206AbZKTVbi (ORCPT ); Fri, 20 Nov 2009 16:31:38 -0500 Received: from bombadil.infradead.org ([18.85.46.34]:34635 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755480AbZKTV22 (ORCPT ); Fri, 20 Nov 2009 16:28:28 -0500 Message-Id: <20091120212508.606459548@chello.nl> References: <20091120211942.676891948@chello.nl> User-Agent: quilt/0.46-1 Date: Fri, 20 Nov 2009 22:19:48 +0100 From: Peter Zijlstra To: Paul Mackerras , Ingo Molnar , Peter Zijlstra Cc: linux-kernel@vger.kernel.org Subject: [PATCH 06/15] perf: optimize perf_event_mmap_ctx() Content-Disposition: inline; filename=perf-event-5.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- kernel/perf_event.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-) Index: linux-2.6/kernel/perf_event.c =================================================================== --- linux-2.6.orig/kernel/perf_event.c +++ linux-2.6/kernel/perf_event.c @@ -3493,15 +3493,10 @@ static void perf_event_mmap_ctx(struct p { 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. --