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SubjectRe: quicklists confuse meminfo
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Andrew Morton <akpm@linux-foundation.org> writes:

> On Sun, 9 Mar 2008 13:34:32 +0100 Ingo Molnar <mingo@elte.hu> wrote:
>
> > the right solution is to get rid of quicklists altogether
>
> Yes, I think so.
>
> - They are pretty marginal from a performance POV (iirc)

One general issue -- as noted again by Christoph Lameter recently --
is that the order 0 fast path in page_alloc.c isn't actually very
fast. That is why people keep inventing their own...

> - As I said when we merged them (under protest): Private object caches
> like this are just a bad idea - caches should be *shared*, because some
> other code path which wants a zeroed page wants a cache-warm one, not a
> cache-cold one from the allocator (iirc there was doubt over how
> cache-warm these pages are, however).
>
> Making __GFP_ZERO smarter/more efficient would be a preferable way of
> addressing any performance problems we have in there.

To do the same as quicklists you would need a __free_pages_zeroed()
and separate buddy lists I think. Later is probably somewhat ugly.
Or perhaps do it only for order 0?

Or perhaps idle time zeroing should be reinvestigated on modern CPUs,
but I'm always a little sceptical of that.

-Andi


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