<html><head><style type='text/css'>p { margin: 0; }</style></head><body><div style='font-family: Arial; font-size: 12pt; color: #000000'>I'm very familiar with nice, but its the taskset command I was referring to, which takes affect at the scheduler:<br><br>http://www.cyberciti.biz/tips/setting-processor-affinity-certain-task-or-process.html<br><br><br>Regards,<br>Scott<br><br><hr id="zwchr"><b>From: </b>"Bob Kline" <bob.kline@gmail.com><br><b>To: </b>"Mailing List for LUG in greater Grand Rapids, MI area." <grlug@grlug.org><br><b>Sent: </b>Thursday, September 22, 2011 12:33:05 PM<br><b>Subject: </b>Re: [GRLUG] FYI - old mysql and new gear<br><br>You can alter the "affinity," whatever<div>that exactly means, but the scheduler</div><div>apparently does not permit assigning</div><div>a CPU to a task, useful as that sometimes</div><div>seems like it would be. In fact, one's control</div>
<div>over how CPU's are assigned seems </div><div>rather limited.</div><div><br></div><div>"Nice" - man nice - has long existed,</div><div>starting in Unix, to allow one to alter</div><div>process priority. If I remember </div>
<div>correctly - if not, that's what man pages</div><div>are for.... - a positive integer, up to 19,</div><div>lowers priority, contrary to one's intuition,</div><div>and can be done by an ordinary user.</div><div>
I believe you have to be root to increase</div><div>priority, a.k.a. "niceness."</div><div><br></div><div>Here again, the scheduler has the last</div><div>word, but it's worth a try.</div><div><br></div><div>
-- Bob</div><div><br></div><div><br><div class="gmail_quote">On Mon, Sep 19, 2011 at 4:45 PM, Michael Mol <span dir="ltr"><<a href="mailto:mikemol@gmail.com" target="_blank">mikemol@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
On Mon, Sep 19, 2011 at 4:36 PM, <<a href="mailto:scott.tanner@comcast.net" target="_blank">scott.tanner@comcast.net</a>> wrote:<br>
> Just thought I'd share an interesting discovery with the group. This may be<br>
> common knowledge to others, but it was a bit of a surprise to me. We're in<br>
> the process of upgrading the servers which run our primary MySQL DB's<br>
> (version 5.1):<br>
><br>
> Old Server New Server<br>
> ---------------------------------------------------------<br>
> Sun X4200 Silicon Mechanics R516<br>
> 4 x 2.4GHz 12 x 3.2GHz (+ HT = 24 threads)<br>
> 16GB Ram 144GB Ram<br>
> 12 disks - SCSI 24 disks - SAS & SSD<br>
><br>
><br>
> After getting the new servers setup and our databases copied over, I ran<br>
> sysbench to get some performance benchmarks of the new servers. Surprise -<br>
> performance was nearly identical or slightly worse. I disabled HT, still no<br>
> real improvement. After a bit of searching on the web, I found the older<br>
> versions of MySQL had issues with multi-threading beyond 8 threads. I setup<br>
> an init script to hot-remove CPU's via sysfs, and voila - performance<br>
> increased substantially. There are patches from Yahoo, Google, and Percona<br>
> to correct this issue on the older MySQL versions, and the newer versions<br>
> are supposedly better at handling 32+ threads.<br>
<br>
Very interesting.<br>
<br>
A thought...Rather than removing your extra cores, perhaps there's<br>
some way to set CPU affinity, so MySQL is only allowed to use eight of<br>
them? That way, the other processes on your system can stay out of the<br>
way of your database server, and spend cycles on other cores.<br>
<br>
If you get affinities working, you might also consider running<br>
multiple instances of mysqld, putting different databases on different<br>
sets of cores.<br>
<br>
<br>
--<br>
:wq<br>
<br>
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