[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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 21:33:04 +0400
User-agent: Mozilla/5.0 (X11; Linux i686; rv:14.0) Gecko/20120714 Thunderbird/14.0

On 07/31/2012 07:43 PM, Peter Maydell wrote:
On 27 July 2012 20:29, Igor Mitsyanko <address@hidden> wrote:
Rather that repeatedly call SD_GET_CLASS() in a loop, call it once before
a loop starts.
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?

-- PMM

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. Although I ran this test several times, I have little faith in test methodology and results, it obviously showed significant dispersion between measured time of distinct 4K writes (200-300% if I recall correctly). I really have no objection no objection to dropping this patch.

reply via email to

[Prev in Thread] Current Thread [Next in Thread]