linux-kernel - kswapd busy but not swapping

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Message-ID: <alpine.DEB.1.10.0805210050440.13780@sheep.housecafe.de>
Date:	Wed, 21 May 2008 01:04:32 +0200 (CEST)
From:	Christian Kujau <lists@...dbynature.de>
To:	LKML <linux-kernel@...r.kernel.org>
cc:	kanoj@...xen.com
Subject: kswapd busy but not swapping

Hi,

I noticed that the [kswapd0] thread was eating 3-7% cpu time but no 
swapspace has been used yet. This is with a just booted 2.6.25.4 system,
currently with some disk i/o going on.

So I figured that kswapd might not be responsible for "swapping" after 
all, although the name suggests it. Grep'ing Documentation/ for kswapd did 
not reveal much. Is the paper from Kanoj[0] still valid for 2.6 kernels? 
The SGI page referenced in Documentation/kernel-docs.txt is down, but 
there's a .txt version on [1] which tells me:

   "When memory runs low, and a process can not find a free page, it wakes
    up kswapd, the memory stealer"

So, if I'd run low on memory, kswapd would be active. But I don't see that 
in free(1):

# free -m
              total       used       free     shared    buffers     cached
Mem:          2023       1662        360          0        820        315
-/+ buffers/cache:        526       1496
Swap:         1505          0       1505

If you're interested, there are more details at 
http://nerdbynature.de/bits/2.6.25.4/kswapd

Thanks,
Christian.

[0] http://reality.sgi.com/kanoj_engr/vm229.html
[1] http://www.cse.unsw.edu.au/~neilb/oss/linux-commentary/
-- 
BOFH excuse #197:

I'm sorry a pentium won't do, you need an SGI to connect with us.
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