linux-kernel - Re: [PATCH v10]: Hibernation: fix the number of pages used for hibernate/thaw buffering

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Message-ID: <4F8AC31B.8010304@debian.org>
Date:	Sun, 15 Apr 2012 14:46:19 +0200
From:	Per Olofsson <pelle@...ian.org>
To:	Bojan Smojver <bojan@...ursive.com>
CC:	"Rafael J. Wysocki" <rjw@...k.pl>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v10]: Hibernation: fix the number of pages used for hibernate/thaw
 buffering

2012-04-12 23:30, Bojan Smojver skrev:
> I was thinking more like this:
> ----------------------
> unsigned long read_pages = 0;
> 
> [...]
> 
> if (low_free_pages() > snapshot_get_image_size())
>        read_pages = (low_free_pages() - snapshot_get_image_size()) / 2;
> read_pages = clamp_val(read_pages, LZO_MIN_RD_PAGES, LZO_MAX_RD_PAGES);
> ----------------------
> 
> Where LZO_MIN_RD_PAGES and LZO_MAX_RD_PAGES are set to 1024 and 8192,
> respectively (this was picked empirically).
> 
> Because we don't really know how many highmem pages are in the image
> (this is figured out by prepare_image() function, half way through
> reading the image - so way after this calculation is done), we assume
> the worst case scenario. And that is that there are no highmem pages in
> the image.
> 
> Given that we cannot use pages from highmem for buffers anyway, the
> above should be careful enough. Of course, there is still some
> possibility of running out of pages, but the kernel is usually in a
> pretty good shape memory-wise on image load, so we should be able to
> squeeze a few MBs out of it, at least.

OK, I see your point now.

Yet another reason to switch to 64-bit then I guess :-)

-- 
Pelle
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