Date: Thu, 8 Jul 2021 08:41:23 +0200 From: Gary Jennejohn <gljennjohn@gmail.com> To: Steve Kargl <sgk@troutmask.apl.washington.edu> Cc: Miroslav Lachman <000.fbsd@quip.cz>, George Mitchell <george+freebsd@m5p.com>, FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Re: Periodic rant about SCHED_ULE Message-ID: <20210708064123.22ae2daf@ernst.home> In-Reply-To: <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> <20210707214919.GA22332@troutmask.apl.washington.edu>
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On Wed, 7 Jul 2021 14:49:19 -0700 Steve Kargl <sgk@troutmask.apl.washington.edu> wrote: > 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 <george+freebsd@m5p.com> 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. > I feel that I have to add that the 40 minute buildworld isn't due to SCHED_4BSD alone, but that I have many features which I don't need disabled in src.conf. I'm pretty sure that a buildworld with every feature enabled would take a lot longer on my system. -- Gary Jennejohn
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