linux-kernel - Re: [PATCH 0/6 v2] PM / Hibernate: Memory bitmap scalability improvements

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Message-ID: <20140728135933.GA5918@pd.tnic>
Date:	Mon, 28 Jul 2014 15:59:33 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Joerg Roedel <joro@...tes.org>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/6 v2] PM / Hibernate: Memory bitmap scalability
 improvements

On Tue, Jul 22, 2014 at 12:34:44PM +0200, Joerg Roedel wrote:
> So my test was to resume from a swap partition that contained no image.
> Here is the result from the 16GB machine. First with a v3.16-rc6 kernel
> without my changes:
> 
> kv:~/base # time perf record /usr/sbin/resume /dev/sda1
> resume: libgcrypt version: 1.5.3
> [ perf record: Woken up 1 times to write data ]
> [ perf record: Captured and wrote 0.019 MB perf.data (~823 samples) ]
> 
> real    0m0.084s
> user    0m0.012s
> sys     0m0.064s
> 
> Here is the result with my patches on top:
> 
> kv:~/hibernate # time perf record /usr/sbin/resume /dev/sda1
> resume: libgcrypt version: 1.5.3
> [ perf record: Woken up 1 times to write data ]
> [ perf record: Captured and wrote 0.014 MB perf.data (~602 samples) ]
> 
> real    0m0.032s
> user    0m0.003s
> sys     0m0.027s
> 
> So we save around 50ms (or 62% of time) already on this 16GB machine.

So, let's see, with Joerg's patches we

- solve the issue on huge boxes. And yes, we most definitely want to be
able to suspend them too. RAS is one very prominent use case here.

*and*

- we see improvement on smaller boxes, above numbers look good to me.

and all that for an additional 8K for a S/R cycle?! And for some
additional complexity of a radix tree which is self-contained, well
tested and understood?

This looks like certainly like net win to me.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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