From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752340AbaILUow (ORCPT ); Fri, 12 Sep 2014 16:44:52 -0400 Received: from mail.kernel.org ([198.145.19.201]:39971 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751998AbaILUov (ORCPT ); Fri, 12 Sep 2014 16:44:51 -0400 Date: Fri, 12 Sep 2014 17:44:44 -0300 From: Arnaldo Carvalho de Melo To: David Ahern Cc: Pawel Moll , Richard Cochran , Steven Rostedt , Ingo Molnar , Peter Zijlstra , Paul Mackerras , John Stultz , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org Subject: Re: [RFC 2/2] perf: Marker software event and ioctl Message-ID: <20140912204444.GA11199@kernel.org> References: <1410522513-1045-1-git-send-email-pawel.moll@arm.com> <1410522513-1045-3-git-send-email-pawel.moll@arm.com> <54132F63.1010401@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <54132F63.1010401@gmail.com> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Em Fri, Sep 12, 2014 at 10:37:39AM -0700, David Ahern escreveu: > On 9/12/14, 4:48 AM, Pawel Moll wrote: > >This patch adds a PERF_COUNT_SW_MARKER event type, which > >can be requested by user and a PERF_EVENT_IOC_MARKER > >ioctl command which will inject an event of said type into > >the perf buffer. The ioctl can take a zero-terminated > >string argument, similar to tracing_marker in ftrace, > >which will be kept in the "raw" field of the sample. > > > >The main use case for this is synchronisation of > >performance data generated in user space with the perf > >stream coming from the kernel. For example, the marker > >can be inserted by a JIT engine after it generated > >portion of the code, but before the code is executed > >for the first time, allowing the post-processor to > >pick the correct debugging information. Other example > >is a system profiling tool taking data from other > >sources than just perf, which generates a marker > >at the beginning at at the end of the session > >(also possibly periodically during the session) to > >synchronise kernel timestamps with clock values > >obtained in userspace (gtod or raw_monotonic). > > Seems really similar to what I proposed in the past: > > https://lkml.org/lkml/2011/2/27/159 > > Which was rejected. I took a look at that thread, but just barely, emphasis on that. Injecting something from userspace, a la ftrace, seems to be something, as tglx mentioned, "buried" in that patchset. - Arnaldo