Date: Mon, 09 Oct 2006 22:28:51 +0200 From: "O. Hartmann" <ohartman@mail.uni-mainz.de> To: Ceri Davies <ceri@submonkey.net>, Maxim Konovalov <maxim@macomnet.ru>, maho@freebsd.org, freebsd-amd64@freebsd.org, freebsd-bugs@freebsd.org Subject: Re: kern/85820: 1.5 times slower performance with SCHED_ULE than SCHED_4BSD Message-ID: <452AB103.8030305@mail.uni-mainz.de> In-Reply-To: <20061008180120.GX21333@submonkey.net> References: <200610081720.k98HKkQx058984@freefall.freebsd.org> <20061008215308.W89071@mp2.macomnet.net> <20061008180120.GX21333@submonkey.net>
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Ceri Davies wrote: > On Sun, Oct 08, 2006 at 09:54:53PM +0400, Maxim Konovalov wrote: > >> On Sun, 8 Oct 2006, 17:20-0000, Ceri Davies wrote: >> >> >>> Synopsis: 1.5 times slower performance with SCHED_ULE than SCHED_4BSD >>> >>> State-Changed-From-To: open->closed >>> State-Changed-By: ceri >>> State-Changed-When: Sun Oct 8 17:19:36 UTC 2006 >>> State-Changed-Why: >>> ULE is no longer the default scheduler, and no longer has a maintainer. >>> This is an interesting test case though. >>> >> I think better mark ULE bugs as suspended. I have plans to take them >> over. >> > > I don't intend to sweep them all. I just didn't see a problem statement > in this PR, and figured that it was due to the fact that ULE was default > at the time the PR was raised. > > Feel free to reopen it if you disagree. > > Ceri > Well, maybe I'm the only 'stupid' in this round, so be patient with me. I never realized, that SCHED_ULE has been discarded from being the default scheduler in FreeBSD 6.X, as I can remember, SCHED_ULE has been promoted to be the default scheduler due to its improvements to SMP. Yesterday I read about some bugs, but I read this in this list and therefore I do not exactly know whether these problems are AMD64 related or also be an issue on i386. Well, let me tell you some remarkeable experiences I made since yesterday. Besides my lab's work I uitilize a FreeBSD 6.2-PRE/AMD64 box with a single core Athlon64 3500+ at 2,2 GHz. This box got really slow when walking through 6.1-STABLE up to now and I tried to figure out why. At my lab's desk I use an i386 based box running a P4 at 3,0 GHz with HT capabilities, enabled both in BIOS and in the system, so this box is configured as a SMP machine. On this box, also using SCHED_ULE, I did never realize the significant performance drop as seen on AMD64. After reading about the scheduler problems, I first changed SCHED_ULE to SCHED_4BSD on my AMD64 box and realized a quite impressive performance boost (something strange and not quantified, because I see this only when working with Firefox, Thunderbird and disk access, which seem to be smoother and quite faster than before). On the lab's box, I changed also scheduler back to SCHED_4BSD, but I did not realize this massive peroformance impact as I did on the AMD64 box. Either this problem is highly related to UP kernel configs and/or UP systems as well or it is only related to the 64Bit FreeBSD or only to AMD CPUs, I do not know but would like to know more about that. Well, 'feeling' a performance impact in both directions isn't a very qualifying statement, so I would like to aks you whether you have some suitable benchmarks I can perform on both boxes to confirm my observations and give some numbers. In the first days of FreeBSD 5.0 I remember myself having seen an impressive performance boost using SCHED_ULE on a dual P3/933 Mhz box acting as a file- and databaseserver, but this advantage has obviously gone over the past. Well, Im not very close to the development issue, I'm only a FreeBSD user for scientific purposes and therefore I would appreciate any public informations on this subject. I guess many others around here still being 'stuck' on a faulty SCHED_ULE, not knowing this scheduler is about to be doomed and slowing down a box. Those guys also may act like me - installing once a system and then migrating from one minor release to the next via cvsupdate/buildworld (due to driver/hardware/support issues) and still keeping a kernel config from days, when SCHED_ULE was said to be the new ultimative scheduler even for SMP and UP boxes. Well, I may be wrong, but it would be much more convenient having those important informations being released more public , this will keep guys like me from sending stupid PRs about slowed down boxes suspecting other hardware or bugs elsewhere in the OS. Thnaks in advance, Oliverhome | help
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