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[77.176.112.195]) by smtp.gmail.com with ESMTPSA id j128-v6sm14644048wmb.43.2018.10.10.04.44.42 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 10 Oct 2018 04:44:43 -0700 (PDT) Date: Wed, 10 Oct 2018 13:44:41 +0200 From: SZEDER =?utf-8?B?R8OhYm9y?= To: Jeff King Cc: Jacob Keller , Jacob Keller , Git mailing list Subject: Re: [PATCH v3] coccicheck: process every source file at once Message-ID: <20181010114441.GD23446@szeder.dev> References: <20181002200710.15721-1-jacob.e.keller@intel.com> <20181005124048.GT23446@localhost> <20181005162517.GB11254@sigill.intra.peff.net> <20181005183904.GV23446@localhost> <20181005190216.GB17482@sigill.intra.peff.net> <20181005195413.GX23446@localhost> <20181009031542.GD6250@sigill.intra.peff.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20181009031542.GD6250@sigill.intra.peff.net> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Mon, Oct 08, 2018 at 11:15:42PM -0400, Jeff King wrote: > On Fri, Oct 05, 2018 at 09:54:13PM +0200, SZEDER Gábor wrote: > > > Runtimes tend to fluctuate quite a bit more on Travis CI compared to > > my machine, but not this much, and it seems to be consistent so far. > > > > After scripting/querying the Travis CI API a bit, I found that from > > the last 100 static analysis build jobs 78 did actully run 'make > > coccicheck' [1], avaraging 470s for the whole build job, with only 4 > > build job exceeding the 10min mark. > > > > I had maybe 6-8 build jobs running this patch over the last 2-3 days, > > I think all of them were over 15min. (I restarted some of them, so I > > don't have separate logs for all of them, hence the uncertainty.) > > So that's really weird and counter-intuitive, since we should be doing > strictly less work. I know that spatch tries to parallelize itself, > though from my tests, 1.0.4 does not. I wonder if the version in Travis > differs in that respect and starts too many threads, and the extra time > is going to contention and context switches. I don't think it does any parallel work. Here is the timing again from my previous email: 960.50user 22.59system 16:23.74elapsed 99%CPU (0avgtext+0avgdata 1606156maxresident)k Notice that 16:23 is 983s, and that it matches the sum of the user and system times. I usually saw this kind of timing with CPU-intensive single-threaded programs, and if there were any parallelization, then I would expect the elapsed time to be at least somewhat smaller than the other two. > Have you tried passing "-j1" to spatch? My 1.0.4 does not even recognize > it. I have just gave it a try, but the v1.0.0 on Travis CI errored out with "unknown option `-j'. https://travis-ci.org/szeder/git/jobs/439532822#L566 > That seems like a pretty unlikely explanation to me, but I am having > trouble coming up with another one. > > I guess the other plausible thing is that the extra memory is forcing us > into some slower path. E.g., a hypervisor may even be swapping, > unbeknownst to the child OS, and it gets accounted in the child OS as > "boy, that memory load was really slow", which becomes used CPU. > > That actually sounds more credible to me. > > -Peff