Date: Fri, 17 Jun 2005 10:50:17 -0400 From: JM <jmartin37@speakeasy.net> To: David Sze <dsze@alumni.uwaterloo.ca> Cc: freebsd-stable@freebsd.org Subject: Re: FreeBSD MySQL still WAY slower than Linux Message-ID: <42B2E329.6000002@speakeasy.net> In-Reply-To: <6.2.1.2.2.20050617103807.058c6fa8@mail.distrust.net> References: <6.2.1.2.2.20050617103807.058c6fa8@mail.distrust.net>
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David Sze wrote: > At 05:15 PM 16/06/2005 +0100, Steve Roome wrote this to All: > >> Thank you all for your suggestions on this thread, here's a brief >> breakdown of most of the ideas from people: >> >> Billy Newsom: COMPILER, DISK, MYSQLVERSION >> Daniel Eischen: +/-HTT, Thread scopes >> Greg Lehey: MALLOC >> Guy Helmer: PREEMPTIVE, vfs.read_max >> Jon Dama: David Xu's Thrds, Ptmalloc, cpu affinity, sched+hwcacheing >> Kris Kennaway: +/-HTT >> Robert Watson: Thread scopes, LIBTHR/Linuxthr on 5 and 6?, LOCKING, >> HTT, SMP/UP >> Thomas Hurst: FreeBSD-current, Don't overload mysql! >> Vladimir Chukharev: COMPILEOPTS, TABLETYPES >> Xin Li: PROFILE, HTT insignificant >> >> The bad news is that I've not managed to get very far at all lately as >> MySQL has been crashing too much to even stop and test stuff >> elsewhere. >> >> The good news though, is that the Mysql folks have agreed to setup >> tests to profile mysql on identical hardware running FreeBSD and Linux >> with an aim to find out exactly where the problem really is. They >> reckon they'll spend at least two weeks trying to find out why Linux >> is so much faster - if they do this right I'd be surprised if we can't >> improve things quite a lot. >> >> Also, it'd be good if any of you who still have an interest in this >> could add any ideas or suggestions that may help *them* with their >> testing. If so, just get in touch with me asap before they get too >> stuck into anything that might prove fruitless. >> >> Here's hoping we can get MySQL running as well on FreeBSD as it ought >> to. > > > > I just spent a couple days comparing MySQL 4.1 performance on: > > FreeBSD/amd64 5.4-RELEASE (libpthread, system and process scope) > FreeBSD/amd64 6.0-CURRENT (libpthread, libthr, system and process scope) > CentOS/amd64 4.0 (i.e. RHEL4.0) > > I couldn't get libthr to work on FreeBSD/amd64 5.4-RELEASE, mysqld > would immediately coredump and the stacktrace looked like it was > corrupted (i.e. hundreds of stack frames, all of which were ???). > > This was the hardware: > > Dell PowerEdge 2850 > Dual Xeon 3.6GHz EMT64, HTT disabled > 4GB RAM > amr RAID controller w/256MB battery backed cache > 5 x 73GB 15K RPM SCSI disks configured as one RAID5 w/64KB stripe > > I was seeing the same sort of super-smack numbers that everyone's been > reporting, i.e. that Linux box was twice as fast as FreeBSD. > > It turns out that the problem was the same thing everyone usually > points the finger at, but no one actually mentioned this time: Linux > mounts its partitions async by default. I don't have the exact numbers > in front of me right now, but these were the ballpark figures (I'm not > going to separate out results for all of the different threading > libraries for FreeBSD because the deltas weren't huge): > > super-smack select-key > 5.4-RELEASE ~20,000 queries/second > 6.0-CURRENT ~24,000 queries/second > CentOS w/async ~36,000 queries/second > CentOS w/sync ~26,000 queries/second > > super-smack update-select > 5.4-RELEASE ~4,000 queries/second > 6.0-CURRENT ~4,500 queries/second > CentOS w/async ~7,500 queries/second > CentOS w/sync ~750 queries/second > > That last CentOS number is not a typo, it was an order of magnitude > slower. I didn't try other file systems on CentOS, just the default > ext3. It's possible that reiserfs or xfs might not be as affected by > switching from async to sync. > > So my production server is now happily running mysql 4.1 on > 6.0-CURRENT :). that explains quite a bit. but why use FreeBSD when you can just turn on async on your partitions and get faster queries?
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