From: Daniel Vetter <daniel@ffwll•ch>
To: Thomas Hellstrom <thellstrom@vmware•com>
Cc: dri-devel@lists•freedesktop.org,
Michel Danzer <daenzer@vmware•com>,
linuxppc-dev@ozlabs•org
Subject: Re: TTM placement & caching issue/questions
Date: Thu, 4 Sep 2014 11:34:54 +0200 [thread overview]
Message-ID: <20140904093454.GG15520@phenom.ffwll.local> (raw)
In-Reply-To: <54081844.7000604@vmware.com>
On Thu, Sep 04, 2014 at 09:44:04AM +0200, Thomas Hellstrom wrote:
> Last time I tested, (and it seems like Michel is on the same track),
> writing with the CPU to write-combined memory was substantially faster
> than writing to cached memory, with the additional side-effect that CPU
> caches are left unpolluted.
>
> Moreover (although only tested on Intel's embedded chipsets), texturing
> from cpu-cache-coherent PCI memory was a real GPU performance hog
> compared to texturing from non-snooped memory. Hence, whenever a buffer
> could be classified as GPU-read-only (or almost at least), it should be
> placed in write-combined memory.
Just a quick comment since this explicitly referes to intel chips: On
desktop/laptop chips with the big shared l3/l4 caches it's the other way
round. Cached uploads are substantially faster than wc and not using
coherent access is a severe perf hit for texturing. I guess the hw guys
worked really hard to hide the snooping costs so that the gpu can benefit
from the massive bandwidth these caches can provide.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
next prev parent reply other threads:[~2014-09-04 9:34 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
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 [this message]
2014-09-04 9:43 ` Benjamin Herrenschmidt
2014-09-04 10:23 ` Thomas Hellstrom
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20140904093454.GG15520@phenom.ffwll.local \
--to=daniel@ffwll$(echo .)ch \
--cc=daenzer@vmware$(echo .)com \
--cc=dri-devel@lists$(echo .)freedesktop.org \
--cc=linuxppc-dev@ozlabs$(echo .)org \
--cc=thellstrom@vmware$(echo .)com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox