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Subject: Re: Please test: workaround to help swapoff behaviour
To: Marcelo Tosatti <marcelo@conectiva.com.br>
Cc: Mike Galbraith <mikeg@wen-online.de>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Derek Glidden <dglidden@illusionary.com>,
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From: "Bulent Abali" <abali@us.ibm.com>
Date: Fri, 8 Jun 2001 19:53:35 -0400
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>> I looked at try_to_unuse in swapfile.c.  I believe that the algorithm is
>> broken.
>> For each and every swap entry it is walking the entire process list
>> (for_each_task(p)).  It is also grabbing a whole bunch of locks
>> for each swap entry.  It might be worthwhile processing swap entries in
>> batches instead of one entry at a time.
>>
>> In any case, I think having this patch is worthwhile as a quick and
dirty
>> remedy.
>
>Bulent,
>
>Could you please check if 2.4.6-pre2+the schedule patch has better
>swapoff behaviour for you?

No problem.  I will check it tomorrow. I don't think it can be any worse
than it is now.  The patch looks correct in principle.
I believe it should go in to 2.4.6.  But I will test it.

On small machines people don't notice it, but otherwise if you have few
GB of memory it really hurts.  Shutdowns take forever since swapoff takes
forever.