Date: Wed, 14 Dec 2011 17:54:15 +0000 From: Tom Evans <tevans.uk@googlemail.com> To: George Mitchell <george+freebsd@m5p.com> Cc: Attilio Rao <attilio@freebsd.org>, freebsd-stable@freebsd.org Subject: Re: SCHED_ULE should not be the default Message-ID: <CAFHbX1%2B5PttyZuNnYot8emTn_AWkABdJCvnpo5rcRxVXj0ypJA@mail.gmail.com> In-Reply-To: <4EE88343.2050302@m5p.com> References: <4EE1EAFE.3070408@m5p.com> <CAJ-FndDniGH8QoT=kUxOQ%2BzdVhWF0Z0NKLU0PGS-Gt=BK6noWw@mail.gmail.com> <4EE2AE64.9060802@m5p.com> <4EE88343.2050302@m5p.com>
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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). 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. 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? 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
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