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List: dm-devel
Subject: Re: [dm-devel] [PATCH] dm-thin: optimize power of two block size
From: Joe Thornber <thornber () redhat ! com>
Date: 2012-06-25 14:09:38
Message-ID: 20120625140938.GB2417 () ubuntu
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On Sun, Jun 24, 2012 at 09:53:22PM -0400, Mikulas Patocka wrote:
> So the conclusion is that is that that divide instruction degrades
> transfer speed, especially on dm-stripe with 4k stripe size (on dm-thin it
> is measurable only with raw read, the difference is smaller because it has
> a minimum chunk size 64k).
>
>
> The question is why do you want to avoid such optimization?
You've conviced me. I just wanted proof, which you've done very
nicely. Thankyou.
> BTW. when unloading the dm-thin device with debugging enabled (the tests
> were done with debugging disabled), I got this message:
> device-mapper: space map checker: free block counts differ, checker
> 131060, sm-disk:130991
> --- so there is supposedly some bug? The kernel is 3.4.3.
That message is ok. I'm going to remove the sm-checker in 3.6. It's
not earning it's keep.
- Joe
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