| From: | Arjen van der Meijden <acmmailing(at)tweakers(dot)net> |
|---|---|
| To: | Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov> |
| Cc: | Mark Wong <markwkm(at)gmail(dot)com>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: linux deadline i/o elevator tuning |
| Date: | 2009-04-09 14:42:28 |
| Message-ID: | 49DE0954.8050606@tweakers.net |
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| Lists: | pgsql-performance |
On 9-4-2009 16:09 Kevin Grittner wrote:
> I haven't benchmarked it, but when one of our new machines seemed a
> little sluggish, I found this hadn't been set. Setting this and
> rebooting Linux got us back to our normal level of performance.
Why would you reboot after changing the elevator? For 2.6-kernels, it
can be adjusted on-the-fly for each device separately (echo 'deadline' >
/sys/block/sda/queue/scheduler).
I saw a nice reduction in load and slowness too after adjusting the cfq
to deadline for a machine that was at its maximum I/O-capacity on a
raid-array.
Apart from deadline, 'noop' should also be interesting for RAID and
SSD-owners, as it basically just forwards the I/O-request to the device
and doesn't do much (if any?) scheduling.
Best regards,
Arjen
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