Low perf with smp
ericd at free.fr
Fri Mar 31 07:19:39 UTC 2006
Thanks a lot Lucas.
What's sound so strange to me is that there we so much difference 30sec=>
54 sec simply by activating smp in kernel.
But I will search on this way and see if it don't come from mysql.
I will send you issue.
----- Original Message -----
From: "Lucas Holt" <luke at foolishgames.com>
To: "Eric" <ericd at free.fr>
Cc: <freebsd-smp at freebsd.org>
Sent: Friday, March 31, 2006 2:00 AM
Subject: Re: Low perf with smp
> As i recall, mysql under FreeBSD 4.x used a userland threads library.
> That means its only capable of being scheduled on 1 cpu at a time and
> each thread is part of one process. I don't think SMP will help you much
> in this case. There have been a number of threads on some of the lists
> (hacker@ ?) in the last few months about MySQL performance indicating it
> might have something to do with the timer, etc. It might be worth
> looking into.
> Some people have stated that FreeBSD 5 and 6 are slower with disk io,
> etc. Plus you've got a raid 1 mirror which will slow down writes. 6.1
> also has a reported issue with the 4bsd scheduler performance. Maybe
> thats part of the problem?
> On Mar 30, 2006, at 11:41 AM, Eric wrote:
>> Mail NETvigieHi all,
>> I buy a new DELL PowerEdge 1850 with Bi-Xeon 2.8GHZ/2*2MB Dual Core
>> 800FSB processor, 2Go DDR2 RAM, PERC4di RAID controller with 2 SCSI U320
>> 15.000tpm 36Go hdd on RAID1.
>> I install on it Freebsd 6.0, apache 2.2.0 and mysql 4.1.18 and compare
>> performance with :
>> OLD PowerEDge with only simple Bi-Xeon 3.0 GHZ and freebsd 4.11.
>> The test is simple mysql query done by php script.
>> Result is that test is two time slower with freebsd 6.0 and dual- core
>> than with old server.
>> I try with and without smp and threaded kernel and results are same.
>> I came back to Generic kernel to see if it come from my kernel
>> configuration but result was same.
>> I then though it come from server and try to upgrade an other one and
>> have same result.
>> I then think it come from 6.0 and try with 6.1 beta4 and see same result
>> I then downgrad to 4.11 without smp and then find good perfs.
>> So I just add to 4.11 generic kernel :
>> options SMP # Symmetric MultiProcessor
>> options APIC_IO # Symmetric (APIC) I/O
>> And then perf go back down from 30secondes to 54 sec.
>> I search a lot on internet and try with this : sysctl
>> But result is same.
>> When doing whith smp top it's just as mysql have to wait to have cpu.
>> During 10,20 sec it just go to 2,4% then grow. Without smp it grow very
>> Does anyone know what's go wrong and what do I have to do to have same
>> perf with smp than without?
>> freebsd-smp at freebsd.org mailing list
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> Lucas Holt
> Luke at FoolishGames.com
> FoolishGames.com (Jewel Fan Site)
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> FoolishGames.net (Enemy Territory site)
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