From: Chris Wilson <chris@chris-wilson.co.uk>
To: Ben Widawsky <ben@bwidawsk.net>, Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: intel-gfx <intel-gfx@lists.freedesktop.org>,
linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH 01/13] drm/i915: fall through pwrite_gtt_slow to the shmem slow path
Date: Mon, 21 Nov 2011 10:20:15 +0000 [thread overview]
Message-ID: <aefc95$2ambkf@orsmga001.jf.intel.com> (raw)
In-Reply-To: <20111120190918.2b138476@bwidawsk.net>
On Sun, 20 Nov 2011 19:09:18 -0800, Ben Widawsky <ben@bwidawsk.net> wrote:
> On Sun, 6 Nov 2011 20:13:48 +0100
> Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
>
> > The gtt_pwrite slowpath grabs the userspace memory with
> > get_user_pages. This will not work for non-page backed memory, like a
> > gtt mmapped gem object. Hence fall throuh to the shmem paths if we hit
> > -EFAULT in the gtt paths.
> >
> > Now the shmem paths have exactly the same problem, but this way we
> > only need to rearrange the code in one write path.
> >
> > v2: v1 accidentaly falls back to shmem pwrite for phys objects. Fixed.
> >
> > Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
>
> It would be nice if there was some way to notify users that pwriting a
> gtt mmapped address can be really damn slow. That's also the one
> behavior change this patch introduces. It's possible that some SW was
> expecting to get a, "fast path" and would deal with the -EFAULT if it
> didn't get it.
The behaviour change is intentional. Before this patch we would
deadlock...
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
next prev parent reply other threads:[~2011-11-21 10:20 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-06 19:13 [PATCH 00/13] pwrite/pread rework Daniel Vetter
2011-11-06 19:13 ` [PATCH 01/13] drm/i915: fall through pwrite_gtt_slow to the shmem slow path Daniel Vetter
2011-11-21 3:09 ` [Intel-gfx] " Ben Widawsky
2011-11-21 10:20 ` Chris Wilson [this message]
2011-11-06 19:13 ` [PATCH 02/13] drm/i915: rewrite shmem_pwrite_slow to use copy_from_user Daniel Vetter
2011-11-21 5:56 ` [Intel-gfx] " Ben Widawsky
2011-11-21 16:02 ` Daniel Vetter
2011-11-21 17:55 ` Ben Widawsky
2011-11-21 18:43 ` Ben Widawsky
2011-11-06 19:13 ` [PATCH 03/13] drm/i915: rewrite shmem_pread_slow to use copy_to_user Daniel Vetter
2011-11-06 19:13 ` [PATCH 04/13] drm/i915: merge shmem_pwrite slow&fast-path Daniel Vetter
2011-11-06 19:13 ` [PATCH 05/13] drm/i915: merge shmem_pread slow&fast-path Daniel Vetter
2011-11-06 19:13 ` [PATCH 06/13] drm: add helper to clflush a virtual address range Daniel Vetter
2011-11-21 19:46 ` [Intel-gfx] " Ben Widawsky
2011-11-06 19:13 ` [PATCH 07/13] drm/i915: move clflushing into shmem_pread Daniel Vetter
2011-11-06 19:13 ` [PATCH 08/13] drm/i915: kill ranged cpu read domain support Daniel Vetter
2011-11-06 19:13 ` [PATCH 09/13] drm/i915: don't use gtt_pwrite on LLC cached objects Daniel Vetter
2011-11-06 21:16 ` Chris Wilson
2011-11-06 22:19 ` Daniel Vetter
2011-11-06 19:13 ` [PATCH 10/13] drm/i915: don't call shmem_read_mapping unnecessarily Daniel Vetter
2011-11-06 19:13 ` [PATCH 11/13] mm: extend prefault helpers to fault in more than PAGE_SIZE Daniel Vetter
2011-11-06 22:24 ` Chris Wilson
2011-11-06 19:13 ` [PATCH 12/13] drm/i915: drop gtt slowpath Daniel Vetter
2011-11-06 19:14 ` [PATCH 13/13] drm/i915: don't clobber userspace memory before commiting to the pread Daniel Vetter
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