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Re: [Qemu-devel] [PATCH V4 10/12] SD card users: optimize access to SDCl

From: Igor Mitsyanko
Subject: Re: [Qemu-devel] [PATCH V4 10/12] SD card users: optimize access to SDClass methods
Date: Tue, 31 Jul 2012 22:03:29 +0400
User-agent: Mozilla/5.0 (X11; Linux i686; rv:14.0) Gecko/20120714 Thunderbird/14.0

On 07/31/2012 09:47 PM, Peter Maydell wrote:
On 31 July 2012 18:33, Igor Mitsyanko <address@hidden> wrote:
On 07/31/2012 07:43 PM, Peter Maydell wrote:
Anthony claims that SD_GET_CLASS should be cheap enough that we don't
need to hoist it out of loops like this. Do you have profiling data
or similar that caused you to write this patch?
Well, I've tested it by measuring an execution time of a 4Kb write to SD
card, results showed that arithmetic mean of time for one 4k write was less
by ~300us in sequence with SD_GET_CLASS extracted from the loop.
How much is that as a % of the total time for the write ?

-- PMM

total write time was ~3.5-4.0 ms I think, so its ~0.08%

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