From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933311Ab3FRT1w (ORCPT ); Tue, 18 Jun 2013 15:27:52 -0400 Received: from mx1.redhat.com ([209.132.183.28]:19689 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932391Ab3FRT1v (ORCPT ); Tue, 18 Jun 2013 15:27:51 -0400 Date: Tue, 18 Jun 2013 21:22:18 +0200 From: Oleg Nesterov To: Steven Rostedt , Peter Zijlstra Cc: Frederic Weisbecker , Ingo Molnar , Masami Hiramatsu , Srikar Dronamraju , "zhangwei(Jovi)" , linux-kernel@vger.kernel.org Subject: [PATCH 3/3] tracing/perf: Avoid perf_trace_buf_*() in perf_trace_##call() when possible Message-ID: <20130618192218.GA19476@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130618192147.GA19443@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org perf_trace_buf_prepare() + perf_trace_buf_submit(task => NULL) make no sense if hlist_empty(head). Change perf_trace_##call() to check ->perf_events beforehand and do nothing if it is empty. However, we can only do this if __task == NULL, so we also add the __builtin_constant_p(__task) check. Signed-off-by: Oleg Nesterov --- include/trace/ftrace.h | 7 ++++++- 1 files changed, 6 insertions(+), 1 deletions(-) diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h index 8886877..04455b8 100644 --- a/include/trace/ftrace.h +++ b/include/trace/ftrace.h @@ -663,6 +663,12 @@ perf_trace_##call(void *__data, proto) \ int rctx; \ \ __data_size = ftrace_get_offsets_##call(&__data_offsets, args); \ + \ + head = this_cpu_ptr(event_call->perf_events); \ + if (__builtin_constant_p(!__task) && !__task && \ + hlist_empty(head)) \ + return; \ + \ __entry_size = ALIGN(__data_size + sizeof(*entry) + sizeof(u32),\ sizeof(u64)); \ __entry_size -= sizeof(u32); \ @@ -677,7 +683,6 @@ perf_trace_##call(void *__data, proto) \ \ { assign; } \ \ - head = this_cpu_ptr(event_call->perf_events); \ perf_trace_buf_submit(entry, __entry_size, rctx, __addr, \ __count, &__regs, head, __task); \ } -- 1.5.5.1