Re: dm-cache warming

[Heinz Mauelshagen <heinzm@redhat.com>]

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..
>