[PATCH] 2.2.1{3,4,5} VM fix

[Andrea Arcangeli]

On Fri, 21 Jan 2000, Alan Cox wrote:

>> The bank gives us 32 pages of credit. We don't need to get the I/O on
>> them. We have a credit that we can use to optimze the I/O.
>
>32 pages, thats 87 ethernet packets. At 100Mbit thats a rather short period
>of time. I make it 1/60th of a second

Actually the 32 pages I was talking about aren't the freepages.min but the
SWAP_CUSTER_MAX.

Anyway I think to see the problem described by Rik and actually I think it
can be fixed by killing the useless polling of 1 second and replacing it
with an unconiditional pre-wakeup of kswapd when GFP touch the
freepages.high watermark. This will in turn should also help performances
and it will try to free the cache from inside kswapd before a process have
to free it itself.

I said "useless polling" exactly because of what you said, that is a
network allocation will eat the freepages.min pages in less than 1 second.

Andrea


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