linux-kernel - Re: uncached page allocator

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Date:	Thu, 30 Aug 2007 17:23:03 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Dave Airlie <airlied@...il.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	dri-devel <dri-devel@...ts.sourceforge.net>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux Memory Management <linux-mm@...ck.org>
Subject: Re: uncached page allocator

Peter Zijlstra wrote:
> On Tue, 2007-08-21 at 16:05 +1000, Dave Airlie wrote:
> 
> 
>>So you can see why some sort of uncached+writecombined page cache
>>would be useful, I could just allocate a bunch of pages at startup as
>>uncached+writecombined, and allocate pixmaps from them and when I
>>bind/free the pixmap I don't need the flush at all, now I'd really
>>like this to be part of the VM so that under memory pressure it can
>>just take the pages I've got in my cache back and after flushing turn
>>them back into cached pages, the other option is for the DRM to do
>>this on its own and penalise the whole system.
> 
> 
> Can't you make these pages part of the regular VM by sticking them all
> into an address_space.
> 
> And for this reclaim behaviour you'd only need to set PG_private and
> have a_ops->releasepage() dtrt.

I'd just suggest Dave just registers a shrinker to start with.

You really want to be able to batch TLB flushes as well, which
->releasepage may not be so good at (you could add more machinery
behind the releasepage to build batches and so on, but anyway, a
shrinker might be the quickest way to get something working).

-- 
SUSE Labs, Novell Inc.
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