Date: Mon, 12 Dec 2011 17:48:54 +0100 From: Gary Jennejohn <gljennjohn@googlemail.com> To: mdf@FreeBSD.org Cc: "O. Hartmann" <ohartman@mail.zedat.fu-berlin.de>, Current FreeBSD <freebsd-current@freebsd.org>, freebsd-stable@freebsd.org, freebsd-performance@freebsd.org, Vincent Hoffman <vince@unsane.co.uk> Subject: Re: SCHED_ULE should not be the default Message-ID: <20111212174854.4f6ea14c@ernst.jennejohn.org> In-Reply-To: <CAMBSHm8WOCyHxUSQHzPJJVuTVykt1JOVGXRvNOsVfrt_oDjATg@mail.gmail.com> References: <4EE1EAFE.3070408@m5p.com> <4EE22421.9060707@gmail.com> <4EE6060D.5060201@mail.zedat.fu-berlin.de> <4EE619FC.4000601@unsane.co.uk> <20111212163221.33d0b8a2@ernst.jennejohn.org> <CAMBSHm8WOCyHxUSQHzPJJVuTVykt1JOVGXRvNOsVfrt_oDjATg@mail.gmail.com>
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On Mon, 12 Dec 2011 08:04:37 -0800 mdf@FreeBSD.org wrote: > On Mon, Dec 12, 2011 at 7:32 AM, Gary Jennejohn > <gljennjohn@googlemail.com> wrote: > > On Mon, 12 Dec 2011 15:13:00 +0000 > > Vincent Hoffman <vince@unsane.co.uk> wrote: > > > >> > >> -----BEGIN PGP SIGNED MESSAGE----- > >> Hash: SHA1 > >> > >> On 12/12/2011 13:47, O. Hartmann wrote: > >> > > >> >> Not fully right, boinc defaults to run on idprio 31 so this isn't an > >> >> issue. And yes, there are cases where SCHED_ULE shows much better > >> >> performance then SCHED_4BSD. [...] > >> > > >> > Do we have any proof at hand for such cases where SCHED_ULE performs > >> > much better than SCHED_4BSD? Whenever the subject comes up, it is > >> > mentioned, that SCHED_ULE has better performance on boxes with a ncpu > > >> > 2. But in the end I see here contradictionary statements. People > >> > complain about poor performance (especially in scientific environments), > >> > and other give contra not being the case. > >> It all a little old now but some if the stuff in > >> http://people.freebsd.org/~kris/scaling/ > >> covers improvements that were seen. > >> > >> http://jeffr-tech.livejournal.com/5705.html > >> shows a little too, reading though Jeffs blog is worth it as it has some > >> interesting stuff on SHED_ULE. > >> > >> I thought there were some more benchmarks floating round but cant find > >> any with a quick google. > >> > >> > >> Vince > >> > >> > > >> > Within our department, we developed a highly scalable code for planetary > >> > science purposes on imagery. It utilizes present GPUs via OpenCL if > >> > present. Otherwise it grabs as many cores as it can. > >> > By the end of this year I'll get a new desktop box based on Intels new > >> > Sandy Bridge-E architecture with plenty of memory. If the colleague who > >> > developed the code is willing performing some benchmarks on the same > >> > hardware platform, we'll benchmark bot FreeBSD 9.0/10.0 and the most > >> > recent Suse. For FreeBSD I intent also to look for performance with both > >> > different schedulers available. > >> > > > > > These observations are not scientific, but I have a CPU from AMD with > > 6 cores (AMD Phenom(tm) II X6 1090T Processor). > > > > My simple test was ``make buildkernel'' while watching the core usage with > > gkrellm. > > > > With SCHED_4BSD all 6 cores are loaded to 97% during the build phase. > > I've never seen any value above 97% with gkrellm. > > > > With SCHED_ULE I never saw all 6 cores loaded this heavily. Usually > > 2 or more cores were at or below 90%. Not really that significant, but > > still a noticeable difference in apparent scheduling behavior. Whether > > the observed difference is due to some change in data from the kernel to > > gkrellm is beyond me. > > SCHED_ULE is much sloppier about calculating which thread used a > timeslice -- unless the timeslice went 100% to a thread, the fraction > it used may get attributed elsewhere. So top's reporting of thread > usage is not a useful metric. Total buildworld time is, potentially. > I suspect you're right since the buildworld time, a much better test, was pretty much the same with 4BSD and ULE. -- Gary Jennejohn
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