Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756223AbZKTVbi (ORCPT ); Fri, 20 Nov 2009 16:31:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756049AbZKTVbg (ORCPT ); Fri, 20 Nov 2009 16:31:36 -0500 Received: from bombadil.infradead.org ([18.85.46.34]:34638 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755671AbZKTV22 (ORCPT ); Fri, 20 Nov 2009 16:28:28 -0500 Message-Id: <20091120212508.378188589@chello.nl> References: <20091120211942.676891948@chello.nl> User-Agent: quilt/0.46-1 Date: Fri, 20 Nov 2009 22:19:45 +0100 From: Peter Zijlstra To: Paul Mackerras , Ingo Molnar , Peter Zijlstra Cc: linux-kernel@vger.kernel.org Subject: [PATCH 03/15] perf: optimize perf_swevent_ctx_event() Content-Disposition: inline; filename=perf-sw-counting-state.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1769 Lines: 56 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 @@ -3886,15 +3886,10 @@ static void perf_swevent_ctx_event(struc { 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_t (*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. -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/