Re: [PATCH 22/29] drm/i915: Handle stolen objects in pwrite

From: Chris Wilson <chris@chris-wilson.co.uk>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH 22/29] drm/i915: Handle stolen objects in pwrite
Date: Thu, 30 Aug 2012 16:09:16 +0100	[thread overview]
Message-ID: <84c8a8$5igho1@orsmga001.jf.intel.com> (raw)
In-Reply-To: <20120820195608.GH5170@phenom.ffwll.local>

On Mon, 20 Aug 2012 21:56:08 +0200, Daniel Vetter <daniel@ffwll.ch> wrote:
> On Sat, Aug 11, 2012 at 03:41:21PM +0100, Chris Wilson wrote:
> > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> 
> What about putting kmap/unmap abstractions into obj->ops (like the dma_buf
> interface already has)? Since the pwrite/pread code is already rather
> branch heave I hope we don't see the overhead of the indirect call even
> in microbenchmarks (haven't checked). And this way we would also neatly
> wrap up dma_bufs for pwrite (if anyone ever really wants that ...).
> 
> The kmap(_atomic) for stolen mem backed objects would boil down to doing
> the pointer arithmetic, kunmap would be just a noop.

Tried doing so. The lack of struct page for the stolen makes it more
cumbersome than it is worth, and worse confusing.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre