Date: Tue, 13 Jun 2000 08:32:23 +0100 From: "Paul Walsh" <paul@walshsimmons.co.uk> To: <freebsd-database@freebsd.org> Subject: FW: Thread issues on FreeBSD 3.4/4.0 with MySQL Message-ID: <015301bfd509$848b3200$7bd1c8c2@nationnet.com>
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Hi Could anybody comment on the following - we are trying to get a pretty busy MySQL server optimised on FreeBSD4.0 having switched from 3.4 after reading on the MySQL list: "if decide to go with FreeBSD, be sure to install the latest 4.0 release as 3.x releases had quite some problems with thread libraries. " and receiving the comments below from Scott Hess Regards, Paul Walsh WALSH SIMMONS The Old Bank, 247 Chapel St, Manchester, UK T:01618399337 F:01618399336 ISDN:01618346884 www.walshsimmons.co.uk Paul mobile: 07714 523312 -----Original Message----- From: Scott Hess [mailto:scott@avantgo.com] Sent: 01 June 2000 18:38 To: Paul Walsh Cc: mysql@lists.mysql.com Subject: RE: Thread problems on FreeBSD 3.4 Hmm, have you done any tests regarding the maximum transactions per second you can push through the database, as measured by iostat? We found that our database performance did not scale with our disk performance, but we really didn't realize how bad it was until we installed a 6-disk RAID array and only saw perhaps %25 performance improvement. Some simple custom test scripts showed 5x performance improvements for similar access patterns. With multiple MySQL daemons running off of the same tables, we were able to realize about 3x performance compared to running a single one. [NOTE: This is on the RAID array, on a single disk we saw nowhere near that improvement.] The basic problem is that the current FreeBSD pthreads implementation makes disk I/O seek-bound and having multiple spindles doesn't help because it can only do a single seek at a time. I'm aware of nothing in FreeBSD4.x that fixes this, though there is work in 5.x that may address the problem. I've also done some modifications to the pthreads library to temporarily fix the problem, but haven't been able to get the patch to production quality, yet. Later, scott On Thu, 1 Jun 2000, Paul Walsh wrote: > We have just installed FreeBSD 4/MySQL 3.22.32 and it is a lot better - > there is more free memory too. > > Scott Hess [mailto:scott@avantgo.com] wrote: >> On Thu, 25 May 2000, Paul Walsh wrote: >> > Are there thread problems / issues on FreeBSD with busy MYSQL >> > servers? >> > >> > Any pointers to documentation/fixes/optimisations for this? >> >> FreeBSD's threading library is implemented such that you cannot have >> multiple pending disk I/O requests. This can limit MYSQL's >> performance, especially on fast hardware (aka RAID arrays). You can >> run multiple MYSQL instances on different ports against the same data >> files to partially address this. _____________________________________________________________________ This message has been checked for all known viruses by Star Internet delivered through the MessageLabs Virus Control Centre. For further information visit http://www.star.net.uk/stats.asp To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-database" in the body of the message
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