Date: Thu, 22 Dec 2011 16:23:29 -0800 From: Adrian Chadd <adrian@freebsd.org> To: Steve Kargl <sgk@troutmask.apl.washington.edu> Cc: freebsd-stable@freebsd.org, Andriy Gapon <avg@freebsd.org> Subject: Re: SCHED_ULE should not be the default Message-ID: <CAJ-VmokeyDrKb-yQkzTm8tnOYcRm603hz%2B6nen10F3zFQVmCEQ@mail.gmail.com> In-Reply-To: <20111222194740.GA36796@troutmask.apl.washington.edu> References: <4EE1EAFE.3070408@m5p.com> <CAJ-FndBSOS3hKYqmPnVkoMhPmowBBqy9-%2BeJJEMTdoVjdMTEdw@mail.gmail.com> <20111215215554.GA87606@troutmask.apl.washington.edu> <CAJ-FndD0vFWUnRPxz6CTR5JBaEaY3gh9y7-Dy6Gds69_aRgfpg@mail.gmail.com> <20111222005250.GA23115@troutmask.apl.washington.edu> <20111222103145.GA42457@onelab2.iet.unipi.it> <20111222184531.GA36084@troutmask.apl.washington.edu> <4EF37E7B.4020505@FreeBSD.org> <20111222194740.GA36796@troutmask.apl.washington.edu>
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On 22 December 2011 11:47, Steve Kargl <sgk@troutmask.apl.washington.edu> w= rote: [snip] Thankyou for posting some actual measurements! > There is the additional observation in one of my 2008 > emails (URLs have been posted) that if you have N+1 > cpu-bound jobs with, say, job0 and job1 ping-ponging > on cpu0 (due to ULE's cpu-affinity feature) and if I > kill job2 running on cpu1, then neither job0 nor job1 > will migrate to cpu1. =A0So, one now has N cpu-bound > jobs running on N-1 cpus. .. and this sounds like a pretty serious regression. Have you ever filed a PR for it? > Finally, my initial post in this email thread was to > tell O. Hartman to quit beating his head against > a wall with ULE (in an HPC environment). =A0Switch to > 4BSD. =A0This was based on my 2008 observations and > I've now wasted 2 days gather additional information > which only re-affirms my recommendation. I personally don't think this is time wasted. You've done something that noone else has actually done - provided actual results from real-life testing, rather than a hundred posts of "I remember seeing X, so I don't use ULE." If you can definitely and consistently reproduce that N-1 cpu bound job bug, you're now in a great position to easily test and re-report KTR/schedtrace results to see what impact they have. Please don't underestimate exactly how valuable this is. How often are those two jobs migrating between CPUs? How am I supposed to read "CPU load" ? Why isn't it just sitting at 100% the whole time? Would you mind repeating this with 4BSD (the N+1 jobs) so we can see how the jobs are scheduled/interleaved? Something tells me we'll see it the jobs being scheduled evenly Adrian
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