Re: [PATCH]: Clean up of __alloc_pages

[Nick Piggin]

Rohit Seth wrote:
> On Sat, 2005-10-29 at 12:33 +1000, Nick Piggin wrote:

> > If you don't do this, then a GFP_HIGH allocator can allocate right
> > down to its limit before it kicks kswapd, then it either will fail or
> > will have to do direct reclaim.
>
>
> You are right if there are only GFP_HIGH requests coming in then the
> allocation will go down to (min - min/2) before kicking in kswapd.
> Though if the requester is not ready to wait, there is another good shot
> at allocation succeed before we get into direct reclaim (and this is
> happening based on can_try_harder flag).

Still, it is a change in behaviour that I would rather not introduce
with a cleanup patch (and is something we don't want to introduce anyway).

So if you could fix that up it would be good.

> > How about moving the zone_statistics up into the 'if (page)'
> > test of get_page_from_freelist? This way we don't have to
> > evaluate page_zone().
>
>
> Let us keep this as is for now.  Will revisit once after the
> pcp_prefer_allocation patches get in place. 

Well page_zone is yet another cacheline that doesn't need to be touched,
and that is introduced by this patch. But the line is likely to be hot,
and get_page_from_freelist does not have the required 'zonelist' which
I didn't notice before.

So OK, revisit this later.

--
SUSE Labs, Novell Inc.

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