linux-kernel - Re: TTM page pool allocator

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Date:	Wed, 22 Jul 2009 15:16:47 +0200
From:	Michel Dänzer <michel@...nzer.net>
To:	Jerome Glisse <glisse@...edesktop.org>
Cc:	Thomas Hellström <thomas@...pmail.org>,
	linux-kernel@...r.kernel.org, dri-devel@...ts.sf.net
Subject: Re: TTM page pool allocator

On Tue, 2009-07-21 at 21:22 +0200, Jerome Glisse wrote:
> On Tue, 2009-07-21 at 20:00 +0200, Jerome Glisse wrote:
> > On Tue, 2009-07-21 at 19:34 +0200, Jerome Glisse wrote:
> > > On Thu, 2009-06-25 at 17:53 +0200, Thomas Hellström wrote:
> > > > 
> > > > 4) We could now skip the ttm_tt_populate() in ttm_tt_set_caching, since 
> > > > it will always allocate cached pages and then transition them.
> > > > 
> > > 
> > > Okay 4) is bad, what happens (my brain is a bit meltdown so i might be
> > > wrong) :
> > > 1 - bo get allocated tt->state = unpopulated
> > > 2 - bo is mapped few page are faulted tt->state = unpopulated
> > > 3 - bo is cache transitioned but tt->state == unpopulated but
> > >     they are page which have been touch by the cpu so we need
> > >     to clflush them and transition them, this never happen if
> > >     we don't call ttm_tt_populate and proceed with the remaining
> > >     of the cache transitioning functions
> > > 
> > > As a workaround i will try to go through the pages tables and
> > > transition existing pages. Do you have any idea for a better
> > > plan ?
> > > 
> > > Cheers,
> > > Jerome
> > 
> > My workaround ruin the whole idea of pool allocation what happens
> > is that most bo get cache transition page per page. My thinking
> > is that we should do the following:
> > 	- is there is a least one page allocated then fully populate
> > 	the object and do cache transition on all the pages.
> > 	- otherwise update caching_state and leaves object unpopulated
> > 
> > This needs that we some how reflect the fact that there is at least
> > one page allocated, i am thinking to adding a new state for that :
> > ttm_partialy_populated
> > 
> > Thomas what do you think about that ?
> > 
> > Cheers,
> > Jerome
> 
> Attached updated patch it doesn't introduce ttm_partialy_populated
> but keep the populate call in cache transition. So far it seems to
> work properly on AGP platform

Yeah, this one works for me as well.

> and helps quite a lot with performances.

Can't say I've noticed that however. How did you measure?


-- 
Earthling Michel Dänzer           |                http://www.vmware.com
Libre software enthusiast         |          Debian, X and DRI developer
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