[GRLUG] FYI - old mysql and new gear

[Bob Kline]

Where are you suggesting "nice"
takes place?

    -- Bob


On Thu, Sep 22, 2011 at 2:20 PM, <scott.tanner at comcast.net> wrote:

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