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

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Date:	Tue, 29 Jul 2014 23:22:39 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Joerg Roedel <joro@...tes.org>, 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 Monday, July 28, 2014 03:59:33 PM Borislav Petkov wrote:
> 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.

Yes, it does.

I've queued up the Joergs patches for 3.17, thanks!

Rafael

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