Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plansfor 2.6.23]

From: Alan Cox
Date: Sun Jul 29 2007 - 13:47:24 EST


> > Is that generally the case on your systems? Every linux system I've
> > run, regardless of RAM, has always pushed things out to swap.
>
> For me, it is generally the case yes. We are still discussing this in the
> context of desktop machines and their problems with being slow as things
> have been swapped out and generally I expect a desktop to have plenty of
> swap which it's not regularly going to fillup significantly since then the
> machine's unworkably slow as a desktop anyway.

A simple log optimises writeout (which is latency critical) and can
otherwise stall an enitre system. In a log you can also have multiple
copies of the same page on disk easily, some stale - so you can write out
chunks of data that are not all them removed from memory, just so you get
them back more easily if you then do (and I guess you'd mark them
accordingly)

The second element is a cleaner - something to go around removing stuff
from the log that is needed when the disks are idle - and also to repack
data in nice linear chunks. So instead of using the empty disk time for
page-in you use it for packing data and optimising future paging.

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