linux-kernel - Re: [PATCH 0/2] drm/i915: Fix ttm small BAR placement handling

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Message-ID: <ZrJLz9rZLsZh1nWo@ashyti-mobl2.lan>
Date: Tue, 6 Aug 2024 17:14:07 +0100
From: Andi Shyti <andi.shyti@...ux.intel.com>
To: David Gow <david@...idgow.net>
Cc: Christian König <ckoenig.leichtzumerken@...il.com>,
	Somalapuram Amaranath <Amaranath.Somalapuram@....com>,
	Thomas Hellström <thomas.hellstrom@...ux.intel.com>,
	Lucas De Marchi <lucas.demarchi@...el.com>,
	Andi Shyti <andi.shyti@...ux.intel.com>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Gow <david@...eniumdigital.com>,
	Jani Nikula <jani.nikula@...ux.intel.com>,
	Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
	Rodrigo Vivi <rodrigo.vivi@...el.com>,
	Tvrtko Ursulin <tursulin@...ulin.net>,
	Ville Syrjälä <ville.syrjala@...ux.intel.com>,
	intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] drm/i915: Fix ttm small BAR placement handling

Hi David,

thanks for the patches and thanks Justin for debugging the issue.

I reviewed and merged it into drm-intel-gt-next.

Thanks,
Andi

On Sun, Aug 04, 2024 at 05:18:46PM +0800, David Gow wrote:
> From: David Gow <david@...eniumdigital.com>
> 
> As described in [1], there have been a couple of regressions in the TTM
> placement handling for i915, which adversely affect DG2 systems with
> small BAR.  In particular, performance become very poor when eviction
> from the mappable BAR memory is required, as suboptimal placements can
> be preferred, leading to thrashing. This often leads to hangs of >10s,
> during which even the compositor is unusable.
> 
> These regressions were largely introduced during the flag rework in
> commit a78a8da51b36 ("drm/ttm: replace busy placement with flags v6").
> 
> The first patch has already been sent out[2]. I'm resending it as part
> of this series which fixes both known regressions.
> 
> Thanks to Justin Brewer for bisecting the issue.
> 
> Cheers,
> -- David
> 
> [1]: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/11255
> [2]: https://lore.kernel.org/dri-devel/20240722074540.15295-1-david@davidgow.net/
> 
> ---
> 
> David Gow (2):
>   drm/i915: Allow evicting to use the requested placement
>   drm/i915: Attempt to get pages without eviction first
> 
>  drivers/gpu/drm/i915/gem/i915_gem_ttm.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
> 
> -- 
> 2.46.0