[dm-devel] dm-cache warming
Heinz Mauelshagen
heinzm at redhat.com
Mon Jul 29 10:16:11 UTC 2013
Hi,
dm-cache is a hot-spot cache. Ie. you need multiple accesses to the same
block to get it promoted into the cache (depending on the policy plugin
btw).
If your patterns is one-time-only access type, it ain't warm the cache.
Heinz
On 07/26/2013 05:24 PM, Dave Pitts wrote:
> Hello:
>
> I've been trying to do some performance testing for a client and can't
> seem to get the dm-cache warmed. The values displayed in the "dmsetup
> status" command seem too low. I've been trying to use the "raw"
> devices setup for the cache and NOT use a file system or database.
> I've tried sequential writes/reads to the devices (ie. dd ) and
> dividing up the space to be tested and do I/O over a number of
> segments to try to break any sequential I/O tests. Any ideas as to
> what I may doing wrong? Do I need to randomize the I/O?
>
> System: RHEL 7.0 Alpha3, 3.9.7 kernel
>
> Thanks in advance..
>
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