From: "Michel Dänzer" <michel@daenzer.net>
To: Jerome Glisse <j.glisse@gmail.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Alex Deucher <alexander.deucher@amd.com>,
linuxppc-dev@ozlabs.org,
Christian Koenig <christian.koenig@amd.com>,
dri-devel@lists.freedesktop.org
Subject: Re: TTM placement & caching issue/questions
Date: Thu, 04 Sep 2014 16:12:14 +0900 [thread overview]
Message-ID: <540810CE.7070107@daenzer.net> (raw)
In-Reply-To: <20140904015548.GB4835@gmail.com>
On 04.09.2014 10:55, Jerome Glisse wrote:
>
> While i agree about the issue of incoherent double map of same page, i
> think we have more issue. For instance lattely AMD have been pushing a
> lot of patches to move things to use uncached memory for radeon and as
> usual thoses patches comes with no comment to the motivations of those
> changes.
That would have been a fair review comment...
> What i understand is that uncached mapping for some frequently use buffer
> give a significant performance boost (i am assuming this has to do with
> all the snoop pci transaction overhead).
Exactly, although it's a win even if the data is written by the CPU only
once and read by the GPU only once.
> This also means that we need to fix ttm_tt_set_placement_caching so that
> when it returns an error it switches to cached mapping. Which will always
> work.
GTT with AGP being one exception.
--
Earthling Michel Dänzer | http://www.amd.com
Libre software enthusiast | Mesa and X developer
next prev parent reply other threads:[~2014-09-04 7:22 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-04 0:12 TTM placement & caching issue/questions Benjamin Herrenschmidt
2014-09-04 1:55 ` Jerome Glisse
2014-09-04 2:07 ` Jerome Glisse
2014-09-04 2:25 ` Benjamin Herrenschmidt
2014-09-04 2:31 ` Jerome Glisse
2014-09-04 2:32 ` Jerome Glisse
2014-09-04 2:36 ` Jerome Glisse
2014-09-04 5:23 ` Benjamin Herrenschmidt
2014-09-04 6:45 ` Gabriel Paubert
2014-09-04 7:19 ` Michel Dänzer
2014-09-04 7:54 ` Benjamin Herrenschmidt
2014-09-04 7:59 ` Michel Dänzer
2014-09-04 7:59 ` Michel Dänzer
2014-09-04 8:07 ` Benjamin Herrenschmidt
2014-09-04 2:15 ` Benjamin Herrenschmidt
2014-09-04 7:12 ` Michel Dänzer [this message]
2014-09-04 7:44 ` Thomas Hellstrom
2014-09-04 8:06 ` Benjamin Herrenschmidt
2014-09-04 8:46 ` Thomas Hellstrom
2014-09-04 9:34 ` Daniel Vetter
2014-09-04 9:43 ` Benjamin Herrenschmidt
2014-09-04 10:23 ` Thomas Hellstrom
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