Re: cp file /dev/zero <-> cache [was Re: increasing page size]

["Stephen C. Tweedie" <sct@redhat.com>]

Hi,

On Thu, 9 Jul 1998 22:39:10 +0200 (CEST), Rik van Riel
<H.H.vanRiel@phys.uu.nl> said:

> On Wed, 8 Jul 1998, Stephen C. Tweedie wrote:
>> <H.H.vanRiel@phys.uu.nl> said:
>> 
>> > When my zone allocator is finished, it'll be a piece of
>> > cake to implement lazy page reclamation.
>> 
>> I've already got a working implementation.  The issue of lazy
>> reclamation is pretty much independent of the allocator underneath; I

> We really should integrate this _now_, with the twist
> that pages which could form a larger buddy should be
> immediately deallocated.

Perhaps, but I don't think Linus will take it.  He's right, too, it's
too near 2.2 for that.

> This can give us a cheap way to:
> - create larger memory buddies
> - remove some of the pressure on the buddy allocator
>   (no need to grab that last 64 kB area when 25% of
>   user pages are lazy reclaim)

All it can do is to reduce the pain of doing swapping too aggressively.
It doesn't make it much easier to do true defragmentation; it just lets
you hang on to the defragmented pages a bit longer, which is a different
thing.  If you end up with non-pagable pages allocated to
kmalloc/slab/page tables all over memory, then lazy reclaim is powerless
to help defrag the memory.  We need something else for 2.2.

--Stephen

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