From: Anthony Liguori <aliguori@us.ibm.com>
To: Igor Mitsyanko <i.mitsyanko@samsung.com>,
Peter Maydell <peter.maydell@linaro.org>
Cc: kwolf@redhat.com, benoit.canet@gmail.com,
wdongxu@linux.vnet.ibm.com, stefanha@linux.vnet.ibm.com,
e.voevodin@samsung.com, qemu-devel@nongnu.org, armbru@redhat.com,
andrew.zaborowski@intel.com, kyungmin.park@samsung.com,
pbonzini@redhat.com
Subject: Re: [Qemu-devel] [PATCH V4 10/12] SD card users: optimize access to SDClass methods
Date: Tue, 31 Jul 2012 13:15:13 -0500 [thread overview]
Message-ID: <87wr1jyez2.fsf@codemonkey.ws> (raw)
In-Reply-To: <501816D0.9040207@samsung.com>
Igor Mitsyanko <i.mitsyanko@samsung.com> writes:
> On 07/31/2012 07:43 PM, Peter Maydell wrote:
>> On 27 July 2012 20:29, Igor Mitsyanko <i.mitsyanko@samsung.com> 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.
How many loop iterations that? 300us is a huge amount of time, unless
you were looping on every byte, I have a hard time understanding that
delta.
Regards,
Anthony Liguori
> 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.
next prev parent reply other threads:[~2012-07-31 18:15 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-27 19:29 [Qemu-devel] [PATCH V4 00/12] SD save/load support, SD qomification and bug fixes Igor Mitsyanko
2012-07-27 19:29 ` [Qemu-devel] [PATCH V4 01/12] hw/sd.c: convert wp_groups in SDState to bitfield Igor Mitsyanko
2012-07-31 14:25 ` Peter Maydell
2012-07-27 19:29 ` [Qemu-devel] [PATCH V4 02/12] hw/sd.c: make sd_wp_addr() accept 64 bit address argument Igor Mitsyanko
2012-07-31 14:25 ` Peter Maydell
2012-07-27 19:29 ` [Qemu-devel] [PATCH V4 03/12] hw/sd.c: introduce wrapper for conversion address to wp group Igor Mitsyanko
2012-07-31 14:27 ` Peter Maydell
2012-07-27 19:29 ` [Qemu-devel] [PATCH V4 04/12] hw/sd.c: favour SD card type (SDSC or SDHC) when performing erase Igor Mitsyanko
2012-07-31 9:29 ` Markus Armbruster
2012-07-31 10:19 ` Igor Mitsyanko
2012-07-31 14:34 ` Peter Maydell
2012-07-31 15:13 ` Igor Mitsyanko
2012-07-27 19:29 ` [Qemu-devel] [PATCH V4 05/12] hw/sd.c: convert binary variables to bool Igor Mitsyanko
2012-07-27 19:29 ` [Qemu-devel] [PATCH V4 06/12] hw/sd.c: make sd_dataready() return bool Igor Mitsyanko
2012-07-27 19:29 ` [Qemu-devel] [PATCH V4 07/12] hw/sd.c: make sd_wp_addr() " Igor Mitsyanko
2012-07-31 14:39 ` Peter Maydell
2012-07-27 19:29 ` [Qemu-devel] [PATCH V4 08/12] hw/sd.c: add SD card save/load support Igor Mitsyanko
2012-07-31 9:33 ` Markus Armbruster
2012-07-31 10:27 ` Igor Mitsyanko
2012-07-31 14:56 ` Peter Maydell
2012-07-31 18:18 ` Igor Mitsyanko
2012-08-08 15:56 ` Peter Maydell
2012-07-27 19:29 ` [Qemu-devel] [PATCH V4 09/12] hw/sd.c: convert SD state to QOM object Igor Mitsyanko
2012-07-31 9:45 ` Markus Armbruster
2012-07-31 9:59 ` Peter Maydell
2012-07-31 14:48 ` Igor Mitsyanko
2012-07-31 15:29 ` Markus Armbruster
2012-07-31 16:17 ` Peter Maydell
2012-07-31 17:09 ` Igor Mitsyanko
2012-07-27 19:29 ` [Qemu-devel] [PATCH V4 10/12] SD card users: optimize access to SDClass methods Igor Mitsyanko
2012-07-31 15:43 ` Peter Maydell
2012-07-31 17:33 ` Igor Mitsyanko
2012-07-31 17:47 ` Peter Maydell
2012-07-31 18:03 ` Igor Mitsyanko
2012-07-31 18:15 ` Anthony Liguori [this message]
2012-07-31 18:33 ` Igor Mitsyanko
2012-07-27 19:29 ` [Qemu-devel] [PATCH V4 11/12] SD card: introduce "spi" property for SD card objects Igor Mitsyanko
2012-07-31 9:54 ` Markus Armbruster
2012-07-31 12:19 ` Andreas Färber
2012-07-31 12:53 ` Paolo Bonzini
2012-07-27 19:29 ` [Qemu-devel] [PATCH V4 12/12] hw/sd.c: introduce SD card "drive" property Igor Mitsyanko
2012-08-10 15:06 ` [Qemu-devel] [PATCH V4 00/12] SD save/load support, SD qomification and bug fixes Peter Maydell
2012-08-10 16:23 ` Igor Mitsyanko
2012-10-25 15:47 ` Peter Maydell
2012-10-25 18:46 ` Igor Mitsyanko
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