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[46.139.12.213]) by smtp.gmail.com with ESMTPSA id v2-v6sm1037398wme.36.2018.09.14.02.33.46 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 14 Sep 2018 02:33:46 -0700 (PDT) Date: Fri, 14 Sep 2018 11:33:44 +0200 From: Ingo Molnar To: Namhyung Kim Cc: Alexey Budankov , Jiri Olsa , Arnaldo Carvalho de Melo , lkml , Alexander Shishkin , Peter Zijlstra , Andi Kleen , kernel-team@lge.com Subject: Re: [RFCv2 00/48] perf tools: Add threads to record command Message-ID: <20180914093344.GA96351@gmail.com> References: <20180913125450.21342-1-jolsa@kernel.org> <20180914022910.GA15146@sejong> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180914022910.GA15146@sejong> 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 * Namhyung Kim wrote: > > > The perf.data stays as a single file. > > I'm not sure we really need to keep it as a single file. As it's a > kind of big changes, we might consider breaking compatibility and use > a directory structure. Agreed - and to make use of the highly scalable Linux VFS implementation we should attempt to use per CPU file resources as well. Any cross-CPU contention should stick out like a sore thumb. > > There is usage of Posix threading API but there is no > > its implementation in the patch series, to avoid dependency > > on externally coded designs in the core of the tool. > > Do you mean it needs to implement its own threading? I don't think > that's what Ingo wanted to. Yeah, I didn't mean that: every libc hoping to work on Linux implements a pthread API, plus the pthread APIs we are using are really just narrow wrappers on top of system calls that were written with libc pthread APIs in mind. So it's not a problem to rely on pthreads.h. (And if we have trouble with any particular pthread detail we can single out specific functionality and not use it or use our own implementation.) The AIO library is another matter: it's a family of interfaces with complex libc specific design choices that cannot be influenced. I.e. my suggestion was to keep using pthreads APIs like we do today, but not use the libc AIO library. Not because there's any problem with glibc AIO: but because basic event flow is a core competency of perf that we want to implement ourselves. Is this clearer? Thanks, Ingo