[Intel-gfx] [PATCH] drm/i915: Don't clflush purged objects on unbind

[Eric Anholt]

On Tue,  8 Dec 2009 22:17:20 +0000, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> If the object is marked as purgeable and we are about to simply truncate
> those pages, don't waste time by clearing the cache lines for the
> object.  In typical usage this saves around 10% of the clflushes.

What I'm concerned about here is a dirtied object: you've now flushed
the GPU cachelines to main memory, but the CPU might be sitting on some
read cachelines (see the madness in the pread path for partial cpu read
domain stuff, though speculation might also cause this).

Could that get us into trouble somehow?  I'm not exactly sure.
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