linux-kernel - Re: [RFC] mm:prototype for the updated swapoff implementation

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Date:	Wed, 19 Feb 2014 23:42:18 +0000
From:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Kelley Nielsen <kelleynnn@...il.com>, riel@...riel.com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	opw-kernel@...glegroups.com, jamieliu@...gle.com,
	sjenning@...ux.vnet.ibm.com, Hugh Dickins <hughd@...gle.com>
Subject: Re: [RFC] mm:prototype for the updated swapoff implementation

> Do you have situations in which swapoff is taking an unacceptable
> amount of time?  If so, please update the changelog to provide full
> details on this, with before-and-after timing measurements.

Yes - because now and then (about once a month) with 3.10 or so + and
encrypted swap my box with 16GB RAM gets into a weird 'slow swapping'
state and only swapoff/swapon gets it back to sanity.

In those cases (and in general) swapoff can take half an hour to run.

There is a reproducer for the swap hang at
https://bugzilla.kernel.org/show_bug.cgi?id=62321

The case I see in normal use (gimp of 1200dpi+ A3 images) hits a crawl
not a hang and does recover but only if you swapoff/swapon again

Alan
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