linux-kernel - Re: TTM page pool allocator

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Date:	Fri, 26 Jun 2009 10:00:32 +1000
From:	Dave Airlie <airlied@...il.com>
To:	Jerome Glisse <glisse@...edesktop.org>
Cc:	thomas@...pmail.org, linux-kernel@...r.kernel.org,
	dri-devel@...ts.sf.net
Subject: Re: TTM page pool allocator

On Thu, Jun 25, 2009 at 10:01 PM, Jerome Glisse<glisse@...edesktop.org> wrote:
> Hi,
>
> Thomas i attach a reworked page pool allocator based on Dave works,
> this one should be ok with ttm cache status tracking. It definitely
> helps on AGP system, now the bottleneck is in mesa vertex's dma
> allocation.
>

My original version kept a list of wb pages as well, this proved to be
quite a useful
optimisation on my test systems when I implemented it, without it I
was spending ~20%
of my CPU in getting free pages, granted I always used WB pages on
PCIE/IGP systems.

Another optimisation I made at the time was around the populate call,
(not sure if this
is what still happens):

Allocate a 64K local BO for DMA object.
Write into the first 5 pages from userspace - get WB pages.
Bind to GART, swap those 5 pages to WC + flush.
Then populate the rest with WC pages from the list.

Granted I think allocating WC in the first place from the pool might
work just as well since most of the DMA buffers are write only.

Dave.
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