kswapd busy but not swapping

From: Christian Kujau
Date: Tue May 20 2008 - 19:05:38 EST


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 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/


[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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