From owner-soc-status@FreeBSD.ORG Tue Mar 18 19:39:35 2014 Return-Path: Delivered-To: soc-status@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 00C66FC2; Tue, 18 Mar 2014 19:39:34 +0000 (UTC) Received: from mail-yh0-x22f.google.com (mail-yh0-x22f.google.com [IPv6:2607:f8b0:4002:c01::22f]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id 7AA592F4; Tue, 18 Mar 2014 19:39:34 +0000 (UTC) Received: by mail-yh0-f47.google.com with SMTP id 29so7437650yhl.6 for ; Tue, 18 Mar 2014 12:39:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=84/H+hdlNplehbqYVJX/4g5xOmPyzw6k718WXcLODco=; b=cOEVHHh6scLEC18cfRdCQiTTv5L7P3G+gfgC462GdmHJuJwq3Z1LJ2w2g30eBzB5yo M8EJUfA6+GVpq/Kk6ODVvhPdEwEa9RtQJGDdiRvEmhv01YZDkfyi2A0KQ9yNQZClCY62 5jrphafGVqZeDhFoVYm5H2loKiovrRv67gZYRIJi1Sfvqz0oN9Rqgr48ZGjVVE31QOu9 VuJi0FRvbWXubK+pq1/pubRQeN6qonwwe3yTZarw5hAiNhK74kb3cJIM53pbkmpuei4e Njv1NFmNTC50tV93EuPBzC6Tv6yhX4h997wkAk2OXnFcLztCHOe1hSJFYe6lkIbjHoai MWRQ== MIME-Version: 1.0 X-Received: by 10.236.177.100 with SMTP id c64mr36560870yhm.30.1395171573780; Tue, 18 Mar 2014 12:39:33 -0700 (PDT) Received: by 10.170.66.204 with HTTP; Tue, 18 Mar 2014 12:39:33 -0700 (PDT) In-Reply-To: <201403181426.19929.jhb@freebsd.org> References: <20140314070218.GA37327@FreeBSD.org> <201403181426.19929.jhb@freebsd.org> Date: Tue, 18 Mar 2014 15:39:33 -0400 Message-ID: Subject: Re: FreeBSD GSOC proposal in 2014 From: yan cui To: John Baldwin Content-Type: text/plain; charset=ISO-8859-1 X-Content-Filtered-By: Mailman/MimeDel 2.1.17 Cc: freebsd-hackers@freebsd.org, freebsd-current@freebsd.org, soc-status@freebsd.org X-BeenThere: soc-status@freebsd.org X-Mailman-Version: 2.1.17 Precedence: list List-Id: Summer of Code Status Reports and Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 18 Mar 2014 19:39:35 -0000 Really? Maybe I can download his code from previous GSoC. Actually, before applying for this idea, I did not scan the projects in previous years and just pick up one which I like. Are there any possibilities to improve on this part (or this idea should not be considered any more)? Yan 2014-03-18 14:26 GMT-04:00 John Baldwin : > On Friday, March 14, 2014 3:02:18 am Wojciech A. Koszek wrote: > > On Thu, Mar 13, 2014 at 09:56:35PM -0400, yan cui wrote: > > > Hi all, > > > > > > I write this mail to make my question clear. I know witness can be > used > > > to detect wrong lock order in the kernel. However, can it be used to do > > > lock profiling (what I mean is to report the information such as which > > > locks are most contended and print some related statistics such as > calling > > > graph, etc)? > > > In other words, is it enough to finish the task by porting witness to > the > > > pthread library? > > > > > > > Yan, > > > > To my knowledge WITNESS is the only tool for lock order verification. > > > > For lock profiling in the FreeBSD kernel there's a KTR subsystem. KTR > > mechanism is basically like syslog() in the user-space, but for the > kernel. > > KTR subsystem will receive messages from KTR API that is placed in the > > FreeBSD kernel. Messages get stored on the list of some sort. List can be > > exported to a file. File you can later analyze. > > > > Jeff wrote a Python app which can be used for pre-processing the KTR logs > > from scheduler and protting them visually. Link: > > > > http://svnweb.freebsd.org/base/head/tools/sched/schedgraph.py > > > > Instead of porting witness to pthreads, maybe we could evaluate expanding > > WITNESS to cover kern_umtx? This could prove to be more universal. > > > > Wojciech > > There is a dedicated lock profiler (LOCK_PROFILING) in the kernel. A > previous GSoC student from an earlier year has already re-implemented both > LOCK_PROFILING and WITNESS for pthreads. > > -- > John Baldwin > -- Think big; Dream impossible; Make it happen.