Date: Thu, 15 Dec 2011 03:05:12 +0100 From: Oliver Pinter <oliver.pntr@gmail.com> To: "O. Hartmann" <ohartman@zedat.fu-berlin.de> Cc: Tom Evans <tevans.uk@googlemail.com>, Attilio Rao <attilio@freebsd.org>, George Mitchell <george+freebsd@m5p.com>, freebsd-stable@freebsd.org Subject: Re: SCHED_ULE should not be the default Message-ID: <CAPjTQNEJDE17TLH-mDrG_-_Qa9R5N3mSeXSYYWtqz_DFidzYQw@mail.gmail.com> In-Reply-To: <4EE933C6.4020209@zedat.fu-berlin.de> References: <4EE1EAFE.3070408@m5p.com> <CAJ-FndDniGH8QoT=kUxOQ%2BzdVhWF0Z0NKLU0PGS-Gt=BK6noWw@mail.gmail.com> <4EE2AE64.9060802@m5p.com> <4EE88343.2050302@m5p.com> <CAFHbX1%2B5PttyZuNnYot8emTn_AWkABdJCvnpo5rcRxVXj0ypJA@mail.gmail.com> <4EE933C6.4020209@zedat.fu-berlin.de>
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On 12/15/11, O. Hartmann <ohartman@zedat.fu-berlin.de> wrote: > On 12/14/11 18:54, Tom Evans wrote: >> On Wed, Dec 14, 2011 at 11:06 AM, George Mitchell >> <george+freebsd@m5p.com> wrote: >>> >>> Dear Secret Masters of FreeBSD: Can we have a decision on whether to >>> change back to SCHED_4BSD while SCHED_ULE gets properly fixed? >>> >> >> Please do not do this. This thread has shown that ULE performs poorly >> in very specific scenarios where the server is loaded with NCPU+1 CPU >> bound processes, and brought forward more complaints about >> interactivity in X (I've never noticed this, and use a FreeBSD desktop >> daily). > > I would highly appreciate a decission against SCHED_ULE as the default > scheduler! SCHED_4BSD is considered a more mature entity and obviously > it seems that SCHED_ULE needs some refinements to achieve a better level > of quality. > >> >> On the other hand, we have very many benchmarks showing how poorly >> 4BSD scales on things like postgresql. We get much more load out of >> our 8.1 ULE DB and web servers than we do out of our 7.0 ones. It's >> easy to look at what you do and say "well, what suits my environment >> is clearly the best default", but I think there are probably more >> users typically running IO bound processes than CPU bound processes. > > You compare SCHED_ULE on FBSD 8.1 with SCHED_4BSD on FBSD 7.0? Shouldn't > you compare SCHED_ULE and SCHED_4BSD on the very same platform? > > Development of SCHED_ULE has been focused very much on DB like > PostgreSQL, no wonder the performance benefit. But this is also a very > specific scneario where SCHED_ULE shows a real benefit compared to > SCHED_4BSD. > >> >> I believe the correct thing to do is to put some extra documentation >> into the handbook about scheduler choice, noting the potential issues >> with loading NCPU+1 CPU bound processes. Perhaps making it easier to >> switch scheduler would also help? > > Many people more experst in the issue than myself revealed some issues > in the code of both SCHED_ULE and even SCHED_4BSD. It would be a pitty > if all the discussions get flushed away like a "toilette-busisness" as > it has been done all the way in the past. > > > Well, I'd like to see a kind of "standardized" benchmark. Like on > openbenchmark.org or at phoronix.com. I know that Phoronix' way of > performing benchmarks is questionable and do not reveal much of the > issues, but it is better than nothing. I'm always surprised by the worse > performance of FreeBSD when it comes to threaded I/O. The differences > between Linux and FreeBSD of the same development maturity are > tremendous and scaring! > > It is a long time since I saw a SPEC benchmark on a FreeBSD driven HPC > box. Most benchmark around for testing hardware are performed with Linux > and Linux seems to make the race in nearly every scenario. It would be > highly appreciable and interesting to see how Linux and FreeBSD would > perform in SPEC on the same hardware platform. This is only an idea. > Without a suitable benchmark with a codebase understood the discussion > is in many aspects pointless -both ways. > > >> >> Cheers >> >> Tom >> >> References: >> >> http://people.freebsd.org/~kris/scaling/mysql-freebsd.png >> http://suckit.blog.hu/2009/10/05/freebsd_8_is_it_worth_to_upgrade >> _______________________________________________ > > Hi! Can you try with this settings: op@opn ~> sysctl kern.sched. kern.sched.cpusetsize: 8 kern.sched.preemption: 0 kern.sched.name: ULE kern.sched.slice: 13 kern.sched.interact: 30 kern.sched.preempt_thresh: 224 kern.sched.static_boost: 152 kern.sched.idlespins: 10000 kern.sched.idlespinthresh: 16 kern.sched.affinity: 1 kern.sched.balance: 1 kern.sched.balance_interval: 133 kern.sched.steal_htt: 1 kern.sched.steal_idle: 1 kern.sched.steal_thresh: 1 kern.sched.topology_spec: <groups> <group level="1" cache-level="0"> <cpu count="2" mask="3">0, 1</cpu> <children> <group level="2" cache-level="2"> <cpu count="2" mask="3">0, 1</cpu> </group> </children> </group> </groups> Most of them from 7-STABLE settings, and with this, "works for me". This an laptop with core2 duo cpu (with enabled powerd), and my kernel config is here: http://oliverp.teteny.bme.hu/freebsd/kernel_conf
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