linux-kernel - Re: [PATCH] PM / Hibernate: Improve performance of LZO/plain hibernation, checksum image

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Date:	Thu, 29 Dec 2011 11:20:12 +0800
From:	Barry Song <21cnbao@...il.com>
To:	Bojan Smojver <bojan@...ursive.com>
Cc:	rjw@...k.pl, linux-pm@...ts.linux-foundation.org,
	LKML <linux-kernel@...r.kernel.org>,
	DL-SHA-WorkGroupLinux <workgroup.linux@....com>
Subject: Re: [PATCH] PM / Hibernate: Improve performance of LZO/plain
 hibernation, checksum image

2011/12/29 Bojan Smojver <bojan@...ursive.com>:
> On Thu, 2011-12-29 at 10:37 +0800, Barry Song wrote:
>> i mean we can load image and decompress them in different threads when
>> we reboot from hibernation. after i read codes more carefully, that
>> has actually been done by lzo_decompress_threadfn().
>
> Correct. Both hibernation and thaw are multi-threaded.
>
>> here the problem is we didn't seem to get any faster after applying
>> your compression patch when doing hibernation on SD/NAND.
>> we are trying to figure out the reason.
>
> This may depend on many factors:
>
> - how much CPU power you have
> - how many CPUs you have
> - how much I/O can your disk do
>
> Remember, there is one thread that does CRC32 as well and other threads
> will have to sync with that thread.
>
> Anyhow, it would be interesting to know where the bottleneck is on your
> particular system. If you system has lots of CPU power and fast I/O, the
> patch indeed may not do anything at all.
>
> PS. I did my testing on a ThinkPad T510 laptop. It has a Core i5 M520
> 2.4 GHz mobile CPU (this appears to the system as 4 CPUs - it's two
> physical cores with hyper-threading enabled). The disk is classic
> platter based disk (Seagate ST9500420AS). There is 8 GB of RAM on this
> system.

well. our guys are still debugging.
the platform is ARM cortex-a9 single-core 1Ghz SoC and we save image
to a SD card or NAND.
a phenomenon we saw is that multi-BIOs is not merged into a request by
block level elevator. so the SD/NANDdisk driver handles many small
request one page by one page.

>
> --
> Bojan
>
-barry
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