[Intel-gfx] Reasons for no ring-buffer on 2.6.27?

[Eric Anholt]

On Wed, 2008-10-15 at 16:48 +0200, Clemens Eisserer wrote:
> Hi,
> 
> I've played a bit with latest intel/xserver git and noticed very poor
> performance on Fedora-10-beta.
> When I execute exactly the same x/driver binaries on a self-compiled
> 2.6.20.1 on Fedora8 performance was as expected (well, actually a bit
> worse than I hoped for ;) )
> 
> What I noticed was that according to sysprof a lot of time was spent
> inside flush-functions like intel-batch-flush (called by
> i830exaDoneSolid ~70% and i830sync ~25%), and that some driver
> initialization messages differ in Xorg.log.
> Any idea why a ring-buffer is initialized and used with 2.6.20.1 and
> it works so well for my testcase, but not with 2.6.27?

Batchbuffers are dispatched through the ringbuffer.  The ring is used in
either case (it's the only way to program acceleration).

This is probably the EXA bug introduced with UXA that keithp said he was
going to fix the other day, but I don't see in the tree yet.  It's there
now.

commit 6707371176147340fabc9ab6f1e3d6d5ac980662
Author: Eric Anholt <eric at anholt.net>
Date:   Wed Oct 15 08:12:11 2008 -0700

    Remove gratuitous flushing in EXA after solid operations.
    
    This snuck in with the UXA rename commit.

Thanks for the sysprof results, it easily reminded me of the correct issue.

-- 
Eric Anholt
eric at anholt.net                         eric.anholt at intel.com


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