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[46.139.12.213]) by smtp.gmail.com with ESMTPSA id 14-v6sm2271698wmp.32.2018.09.14.05.45.48 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 14 Sep 2018 05:45:48 -0700 (PDT) Date: Fri, 14 Sep 2018 14:45:46 +0200 From: Ingo Molnar To: Jiri Olsa Cc: Peter Zijlstra , Namhyung Kim , Alexey Budankov , Jiri Olsa , Arnaldo Carvalho de Melo , lkml , Alexander Shishkin , Andi Kleen , kernel-team@lge.com Subject: Re: [RFCv2 00/48] perf tools: Add threads to record command Message-ID: <20180914124546.GB98534@gmail.com> References: <20180913125450.21342-1-jolsa@kernel.org> <20180914022910.GA15146@sejong> <20180914082307.GF24224@krava> <20180914094022.GB96351@gmail.com> <20180914111528.GH24124@hirez.programming.kicks-ass.net> <20180914114725.GB17042@krava> <20180914120129.GJ24124@hirez.programming.kicks-ass.net> <20180914121307.GA98534@gmail.com> <20180914121940.GA9737@krava> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180914121940.GA9737@krava> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Jiri Olsa wrote: > On Fri, Sep 14, 2018 at 02:13:07PM +0200, Ingo Molnar wrote: > > > > * Peter Zijlstra wrote: > > > > > On Fri, Sep 14, 2018 at 01:47:25PM +0200, Jiri Olsa wrote: > > > > On Fri, Sep 14, 2018 at 01:15:28PM +0200, Peter Zijlstra wrote: > > > > > On Fri, Sep 14, 2018 at 11:40:22AM +0200, Ingo Molnar wrote: > > > > > > In fact keeping the files separate has scalability advantages for 'perf report' and similar > > > > > > parsing tools: they could read all the streams in a per-CPU fashion already, from the very > > > > > > beginning. > > > > > > > > > > Also writing to different files from different CPUs is good for record, > > > > > less contention on the inode state (which include pagecache). > > > > > > > > maybe I should explain a little bit more on this > > > > > > > > we write to different (per-cpu) files during the record, > > > > and at the end of the session, we take them and store > > > > them inside perf.data > > > > > > How long does it take to combine that? If we generated a lot of data, > > > that could take a fair amount of time, no? > > yep.. fair amount ;-) wasn't that bad in my tests, > but could be evil on some really big server Also, adding any sort of 'global' processing to the end of a session sucks as a workflow principle: perf record should ideally be as lightweight as ftrace. It should trace and that's it - the processing should be done at the report phase. Shuffling hundreds of megs or gigs around at the end of the session is really bad. > > Agreed - plus at the report stage it would be advantageous to be able to *read* per-cpu files > > as well. > > > > If we do things smartly them report will create similar NUMA affinity as the record session > > used. > > ok, separate files it is Thanks!! Ingo