Re: kswapd problem?

David Burrows (
Tue, 3 Mar 1998 09:36:24 +1000 (EST)

On Mon, 2 Mar 1998, Bill Hawes wrote:

> In looking through the revised kswapd code it appears to me that under some
> circumstances the kswapd process would fail to sleep even after repeated
> failures, stopping only when the memory objective had been reached.
> Since the task state is set to TASK_INTERRUPTIBLE after the call to schedule(),
> a blocking call to try_to_free_page() could cause the state to get set back to
> TASK_RUNNING, which would cause it to fall through the next schedule() and do
> the loop again.

This would explain why the hard disk chomps away sometimes, in a
repetetive sounding manner (sounds like ch clunk ch clunk ch clunk.. etc),
and during this time the system is completely blocked from doing anything.
Usually after a few seconds it comes back to life and everything is happy
(until a few minutes later or whenever when it decides to do it again).. I
started seeing this behaviour about the same time pre-2.1.89-1 came out,
but it was much much worse than pre-3.. (I havn't tried pre-5 yet because
I can't be bothered re-applying the irq diff, and the diffs to get smbfs
working, unless this has been fixed, and I assumed the swap code hasn't
been touched either)..

> It seems like this could account for some of the reports of overly-aggressive
> swapping in 2.1.89-5. Have I missed something here, or is this the intended
> behavior?

I'd say you've hit the nail with the middle of the hammer, so to speak. :)



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