Date: Fri, 22 Feb 2008 09:35:45 -0500 From: benjamin thielsen <bthielsen@safarivideonetworks.com> To: freebsd-performance@freebsd.org Subject: Re: performance degradation in 6.2 when adding a second quad core chip Message-ID: <2E9A88C1-067C-4C9C-A062-42203F47BF1C@safarivideonetworks.com> In-Reply-To: <47BE0016.6020407@FreeBSD.org> References: <C884D1B7-6D00-4D50-A1D5-FA04F533F757@safarivideonetworks.com> <47BE0016.6020407@FreeBSD.org>
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On Feb 21, 2008, at 17.49, Kris Kennaway wrote: > benjamin thielsen wrote: >> hi folks- >> we've been experiencing some interesting behavior on single quad >> core computers as compared to dual quad core computers. > > Yes, this can happen when you run into concurrency bottlenecks in > the application or in the kernel. > >> it appears that adding a second processor to the system (leaving it >> otherwise untouched) actually decreases performance. we've got a >> small rudimentary test process, built in house, that does >> postgresql queries (selects) via http requests (apache2/php5). > > 7.0 will perform much better than 6.x on SMP workloads in general, > however TCP I/O is not yet at the point where it can make efficient > use of many processors (there has been a lot of work on TCP in 7.0, > but it is not yet at the stage where a performance payoff will be > seen with more than about 4 CPUs). This is one of the projects that > we will be working on this year, so you can expect future releases > to have improved concurrent TCP performance. > > There may be other issues, so if you like you can enable > LOCK_PROFILING and obtain a trace when your workload is running (see > the manpage). You should also try the ULE scheduler on 7.0. i apologize - i neglected to mention that we are using ule on 7.0. what do you guys generally endorse/recommend for local(non-network) load/performance testing? -ben
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