From nobody Wed Jul 07 21:49:19 2021 X-Original-To: freebsd-hackers@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 6D63A122238A for ; Wed, 7 Jul 2021 21:49:28 +0000 (UTC) (envelope-from sgk@troutmask.apl.washington.edu) Received: from troutmask.apl.washington.edu (troutmask.apl.washington.edu [128.95.76.21]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (2048 bits) client-digest SHA256) (Client CN "troutmask", Issuer "troutmask" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 4GKtP41SChz3jdN for ; Wed, 7 Jul 2021 21:49:27 +0000 (UTC) (envelope-from sgk@troutmask.apl.washington.edu) Received: from troutmask.apl.washington.edu (localhost [127.0.0.1]) by troutmask.apl.washington.edu (8.16.1/8.16.1) with ESMTPS id 167LnKqm022389 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Wed, 7 Jul 2021 14:49:20 -0700 (PDT) (envelope-from sgk@troutmask.apl.washington.edu) Received: (from sgk@localhost) by troutmask.apl.washington.edu (8.16.1/8.16.1/Submit) id 167LnJms022388; Wed, 7 Jul 2021 14:49:19 -0700 (PDT) (envelope-from sgk) Date: Wed, 7 Jul 2021 14:49:19 -0700 From: Steve Kargl To: Miroslav Lachman <000.fbsd@quip.cz> Cc: gljennjohn@gmail.com, George Mitchell , FreeBSD Hackers Subject: Re: Periodic rant about SCHED_ULE Message-ID: <20210707214919.GA22332@troutmask.apl.washington.edu> References: <13445948-7804-20b4-4ae6-aaac14d11e87@m5p.com> <20210707181835.75601d54@ernst.home> <054b4735-7740-617d-6c61-c5b48ef1d85a@quip.cz> List-Id: Technical discussions relating to FreeBSD List-Archive: https://lists.freebsd.org/archives/freebsd-hackers List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-hackers@freebsd.org MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <054b4735-7740-617d-6c61-c5b48ef1d85a@quip.cz> X-Rspamd-Queue-Id: 4GKtP41SChz3jdN X-Spamd-Bar: ---- Authentication-Results: mx1.freebsd.org; none X-Spamd-Result: default: False [-4.00 / 15.00]; TAGGED_RCPT(0.00)[freebsd]; REPLY(-4.00)[] X-ThisMailContainsUnwantedMimeParts: N On Wed, Jul 07, 2021 at 10:56:55PM +0200, Miroslav Lachman wrote: > On 07/07/2021 20:18, Gary Jennejohn wrote: > > On Wed, 7 Jul 2021 13:47:47 -0400 > > George Mitchell wrote: > > [..] > > > > I've been ranting about this for years now, and I've had my say -- but > > > no one has ever answered my question about what workload SCHED_ULE is > > > best for, though numerous people have claimed that it's better than > > > SCHED_4BSD for -- some rumored workload or other. -- George > > > > > > > IIRC there was talk about making the scheduler loadable in the early > > days. But that was years ago and I may be misrembering. > > > > I have a Ryzen 5 1600 with 6 cores, so older tech and "only" 3200MHz. > > > > I can do a clean buildworld on FreeBSD-14 using only 10 of the 12 SMTs > > in about 40 minutes using SCHED_4BSD. While still browsing the > > interwebs or watching a film etc. with no noticeable lags in > > performance. > > > > So, for my normal desktop usage SCHED_4BSD is the only way to go. > > I had some performance problems with VirtualBox as hypervisor on somewhat > older Intel Xeon with 4 cores 8 threads. So I tested 4BSD and ULE - > SCHED_4BSD had slightly better results than SCHED_ULE. > I am also curious why ULE is the default. Where are some real world > performance results for comparing the two FreeBSD schedulers. > I made those measurements more than a decade ago, and reported my findings in either freebsd-hackers or freebsd-current mailing list. Write a classic boss-worker MPI numerical simulation, where the workers are compute bound. Start the MPI simulation requesting NCPU+1 images with NCPU being the number of available cpus. Each worker will be assigned to a cpu. Then this leads to a worker and the boss image sharing a cpu. Due to cpu affinity, these two then ping-pong on that cpu. I haven't repeated these measurement in a long time. -- Steve