linux-kernel - Re: [PATCH 1/2] mm: prevent to add a page to swap if may

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Date:	Thu, 10 Jan 2013 15:27:32 -0800
From:	Luigi Semenzato <semenzato@...gle.com>
To:	Minchan Kim <minchan@...nel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Dan Magenheimer <dan.magenheimer@...cle.com>,
	Sonny Rao <sonnyrao@...gle.com>,
	Bryan Freed <bfreed@...gle.com>,
	Hugh Dickins <hughd@...gle.com>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH 1/2] mm: prevent to add a page to swap if may_writepage is unset

[I may have screwed up my previous message, sorry if this is a
duplicate.  (Content-Policy reject msg: The message contains HTML
subpart, therefore we consider it SPAM or Outlook Virus.)]

------------------------------------------

For what it's worth, I tested this patch on my 3.4 kernel, and it
works as advertised.  Here's my setup.

- 2 GB RAM
- a 3 GB zram disk for swapping
- start one "hog" process per second (each hog process mallocs and
touches 200 MB of memory).
- watch /proc/meminfo

1. I verified that the problem still exists on my current 3.4 kernel.
With laptop_mode = 2, hog processes are oom-killed when about 1.8-1.9
(out of 3) GB of swap space are still left

2. I double-checked that the problem does not exist with laptop_mode =
0: hog processes are oom-killed when swap space is exhausted (with
good approximation).

3. I added the two-line patch, put back laptop_mode = 2, and verified
that hog processes are oom-killed when swap space is exhausted, same
as case 2.

Let me know if I can run any more tests for you, and thanks for all
the support so far!
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