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Re: [dm-devel] dm-cache warming




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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