From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932895Ab3JOOc5 (ORCPT ); Tue, 15 Oct 2013 10:32:57 -0400 Received: from mail-vb0-f44.google.com ([209.85.212.44]:54077 "EHLO mail-vb0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932272Ab3JOOcz (ORCPT ); Tue, 15 Oct 2013 10:32:55 -0400 Date: Tue, 15 Oct 2013 11:32:45 -0300 From: Arnaldo Carvalho de Melo To: David Ahern Cc: Ingo Molnar , linux-kernel@vger.kernel.org, Frederic Weisbecker , Peter Zijlstra , Jiri Olsa , Namhyung Kim , Mike Galbraith , Stephane Eranian Subject: Re: [PATCH 3/3] perf record: mmap output file Message-ID: <20131015143245.GB9828@ghostprotocols.net> References: <1381289214-24885-1-git-send-email-dsahern@gmail.com> <1381289214-24885-4-git-send-email-dsahern@gmail.com> <20131009055957.GA7664@gmail.com> <525D4B5F.4090005@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <525D4B5F.4090005@gmail.com> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Em Tue, Oct 15, 2013 at 08:04:15AM -0600, David Ahern escreveu: > On 10/8/13 11:59 PM, Ingo Molnar wrote: > > 2) > > Yet another method would be to avoid the copies altogether via the splice > > system-call - see: > > git grep splice kernel/trace/ > > To make splice low-overhead we'd have to introduce a mode to not mmap > > the data part of the perf ring-buffer and splice the data straight > > from the perf fd into a temporary pipe and over from the pipe into > > the target file (or socket). > I looked into splice and it was not clear it would be a good match. > First, perf is setup to pull data from mmap's and there is not a 1:1 > association between mmap's and fd's (fd_in for splice). Second and Jiri and PeterZ probaby will have comments here... ;-) :-) Jiri even have patches, IIRC. - Arnaldo