linux-kernel - Re: swapping when there's a free memory

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Message-ID: <20100425071349.GA1275@ucw.cz>
Date:	Sun, 25 Apr 2010 09:13:49 +0200
From:	Pavel Machek <pavel@....cz>
To:	Mikulas Patocka <mikulas@...ax.karlin.mff.cuni.cz>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...r.kernel.org
Subject: Re: swapping when there's a free memory

Hi!

> I captured this output of vmstat. The machine was freeing cache and 
> swapping out pages even when there was a plenty of free memory.
> 
> The machine is sparc64 with 1GB RAM with 2.6.34-rc4. This abnormal 
> swapping happened during running spadfsck --- a fsck program for a custom 
> filesystem that caches most reads in its internal cache --- so it reads 
> buffers and allocates memory at the same time.
> 
> Note that sparc64 doesn't have any low/high memory zones, so it couldn't 
> be explained by filling one zone and needing to allocate pages in it.

Fragmented memory + high-order allocation?

> This abnormal behavior doesn't happen everytime, it happend about twice 
> for many spadfsck attempts.

...yep, that would be random.
								Pavel


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