Message-ID: <4FA797C1.7040603@googlemail.com>
Date: Mon, 07 May 2012 11:37:05 +0200
From: Martin Grotzke <martin.grotzke@googlemail.com>
User-Agent: Mozilla/5.0 (X11; Linux x86_64;
	rv:12.0) Gecko/20120424 Thunderbird/12.0
MIME-Version: 1.0
To: Albe Laurenz <laurenz.albe@wien.gv.at>
CC: pgsql-performance@postgresql.org
Subject: Re: Several optimization options (config/hardware)
References: <4FA13444.4050501@googlemail.com>
	<D960CB61B694CF459DCFB4B0128514C207D4FCC1@exadv11.host.magwien.gv.at>
	<4FA281C4.6040104@googlemail.com>
	<D960CB61B694CF459DCFB4B0128514C207D5012C@exadv11.host.magwien.gv.at>
In-Reply-To: 
 <D960CB61B694CF459DCFB4B0128514C207D5012C@exadv11.host.magwien.gv.at>
Content-Type: multipart/signed; micalg=pgp-sha1;
	protocol="application/pgp-signature";
	boundary="------------enigE93C6AC1919751FCC5242981"

This is an OpenPGP/MIME signed message (RFC 2440 and 3156)
--------------enigE93C6AC1919751FCC5242981
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable

On 05/04/2012 09:57 AM, Albe Laurenz wrote:
> Martin Grotzke wrote:
>>> You could try different kernel I/O elevators and see if that
>>> improves something.
>>>=20
>>> I have made good experiences with elevator=3Ddeadline and
>>> elevator=3Dnoop.
>=20
>> Ok, great info.
>>=20
>> I'm not sure at which device to look honestly to check the current=20
>> configuration.
>>=20
>> mount/fstab shows the device /dev/mapper/VG01-www for the relevant=20
>> partition. When I check iostat high utilization is reported for
>> the devices dm-4 and sda (showing nearly the same numbers for util
>> always),
>> so I suspect that dm-4 is mapped on sda.
>=20
> Use the option -N of "iostat" to see long device names. You can use
> "lvm" to figure out the mapping.
iostat with -N shows VG01-www for dm-4. For lvm/lvdisplay/dmsetup I get
"Permission denied" as I have no root/sudo permissions. I need to check
this with our hosting provider (hopefully we have a call today).


>> This is the current config: $ cat /sys/block/sda/queue/scheduler=20
>> noop anticipatory deadline [cfq] $ cat
>> /sys/block/dm-4/queue/scheduler none
>=20
> Do you mean literal "none" or do you mean that the file is empty?
"none" was the output of `cat /sys/block/dm-4/queue/scheduler`.


>> Which of them should be changed? I'll discuss this also with our
>> hosting provider next week, he'll know what has to be done.
>=20
> I'd just add "elevator=3Ddeadline" to the kernel line in
> /etc/grub.conf and reboot.  At least if it is a dedicated database
> machine.
>=20
> But of course you want to change it on the fly first to test - not=20
> knowing the answer to your question, I would change it in both
> devices if I can.
Ok, makes sense.

Cheers,
Martin


--------------enigE93C6AC1919751FCC5242981
Content-Type: application/pgp-signature; name="signature.asc"
Content-Description: OpenPGP digital signature
Content-Disposition: attachment; filename="signature.asc"

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.12 (GNU/Linux)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/

iEYEARECAAYFAk+nl8IACgkQ7FvOl7Te+pYekgCfVG28/rpXAStcV+R4XR2e7wSq
swgAoLG1tKffUknjKkr5DBuV7dFr++X4
=GE33
-----END PGP SIGNATURE-----

--------------enigE93C6AC1919751FCC5242981--