From owner-freebsd-stable@freebsd.org Wed Nov 2 14:23:33 2016 Return-Path: Delivered-To: freebsd-stable@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 2BC5FC2A3F4 for ; Wed, 2 Nov 2016 14:23:33 +0000 (UTC) (envelope-from george+freebsd@m5p.com) Received: from mailhost.m5p.com (mailhost.m5p.com [IPv6:2001:418:3fd::f7]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id A45B116EB for ; Wed, 2 Nov 2016 14:23:32 +0000 (UTC) (envelope-from george+freebsd@m5p.com) Received: from [10.100.0.31] (haymarket.m5p.com [10.100.0.31]) by mailhost.m5p.com (8.15.2/8.15.2) with ESMTP id uA2ENOCL012016; Wed, 2 Nov 2016 10:23:29 -0400 (EDT) (envelope-from george+freebsd@m5p.com) Subject: Re: huge nanosleep variance on 11-stable To: freebsd-stable@freebsd.org References: <6167392c-c37a-6e39-aa22-ca45435d6088@gmail.com> <1c3f4599-8aef-471a-3a39-49d913f1a4e5@gmail.com> From: George Mitchell Cc: rkoberman@gmail.com, jason.harmening@gmail.com Message-ID: Date: Wed, 2 Nov 2016 10:23:24 -0400 User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.4.3 (mailhost.m5p.com [10.100.0.247]); Wed, 02 Nov 2016 10:23:30 -0400 (EDT) X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 02 Nov 2016 14:23:33 -0000 On 11/01/16 23:45, Kevin Oberman wrote: > On Tue, Nov 1, 2016 at 2:36 PM, Jason Harmening > 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