Date: Wed, 2 Nov 2016 10:23:24 -0400 From: George Mitchell <george+freebsd@m5p.com> To: freebsd-stable@freebsd.org Cc: rkoberman@gmail.com, jason.harmening@gmail.com Subject: Re: huge nanosleep variance on 11-stable Message-ID: <c156c04a-fd79-a1e8-1336-3fb1ed5b5b79@m5p.com> In-Reply-To: <CAN6yY1vKr_PAHp3bL-iiHndPxq58kz_qFqmjbEcK1CbmhywVZg@mail.gmail.com> References: <c88341e2-4c52-ed3c-a469-6446da4415f4@gmail.com> <6167392c-c37a-6e39-aa22-ca45435d6088@gmail.com> <1c3f4599-8aef-471a-3a39-49d913f1a4e5@gmail.com> <CAN6yY1vKr_PAHp3bL-iiHndPxq58kz_qFqmjbEcK1CbmhywVZg@mail.gmail.com>
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On 11/01/16 23:45, Kevin Oberman wrote: > On Tue, Nov 1, 2016 at 2:36 PM, Jason Harmening <jason.harmening@gmail.com> > wrote: > >> Sorry, that should be ~*30ms* to get 30fps, though the variance is still >> up to 500ms for me either way. >> >> On 11/01/16 14:29, Jason Harmening wrote: >>> repro code is at http://pastebin.com/B68N4AFY if anyone's interested. >>> >>> On 11/01/16 13:58, Jason Harmening wrote: >>>> Hi everyone, >>>> >>>> I recently upgraded my main amd64 server from 10.3-stable (r302011) to >>>> 11.0-stable (r308099). It went smoothly except for one big issue: >>>> certain applications (but not the system as a whole) respond very >>>> sluggishly, and video playback of any kind is extremely choppy. >>>> >>>> [...] > I eliminated the annoyance by change scheduler from ULE to 4BSD. That was > it, but I have not seen the issue since. I'd be very interested in whether > the scheduler is somehow impacting timing functions or it's s different > issue. I've felt that there was something off in ULE for some time, but it > was not until these annoying hiccups convinced me to try going back to > 4BSD. > > Tip o' the hat to Doug B. for his suggestions that ULE may have issues that > impacted interactivity. > [...] Not to beat a dead horse, but I've been a non-fan of SCHED_ULE since it was first introduced, and I don't like it even today. I run the distributed.net client on my machines, but even without that, ULE screws interactive behavior. With distributed.net running and ULE, a make buildworld/make buildkernel takes 10 2/3 hours on 10.3-RELEASE on a 6-CPU machine versus 2 1/2 hours on the same machine with 4BSD and distributed.net running. I'm told that SCHED_ULE is the greatest thing since sliced bread for some compute load or other (details are scarce), but I (fortunately) don't often have to run heavy server type loads; and for everyday use (even without distributed.net running), SCHED_4BSD is my choice by far. It's too bad I can't run freebsd_update with it, though. I promise to shut up about this now. -- George
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