[Intel-gfx] [PATCH] drm/i915: Disable THP until we have a GPU read BW W/A

Rantala, Valtteri valtteri.rantala at intel.com
Mon Nov 27 13:36:57 UTC 2017


> -----Original Message-----
> From: Joonas Lahtinen [mailto:joonas.lahtinen at linux.intel.com]
> Sent: Monday, November 27, 2017 11:13 AM
> To: Intel graphics driver community testing & development <intel-
> gfx at lists.freedesktop.org>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>; Auld, Matthew
> <matthew.auld at intel.com>; Chris Wilson <chris at chris-wilson.co.uk>; Jani
> Nikula <jani.nikula at linux.intel.com>; Vivi, Rodrigo <rodrigo.vivi at intel.com>;
> Rantala, Valtteri <valtteri.rantala at intel.com>; Tamminen, Eero T
> <eero.t.tamminen at intel.com>
> Subject: [PATCH] drm/i915: Disable THP until we have a GPU read BW W/A
> 
> We seem to be missing some W/A for 2M pages and are getting a hit on raw
> GPU read bandwidths (even 30%) even though the GPU write bandwidths
> improve (even 10%).
> 
> For now, disable THP, which is our only practical source of 2M pages until we
> have a W/A for the issue.
> 
> v2:
> - Be explicit that we talk about GPU bandwidths (Eero)
> - s/deny/never/ because that's why (Chris)
> 
> Reported-by: Valtteri Rantala <valtteri.rantala at intel.com>
> Fixes: b901bb89324a ("drm/i915/gemfs: enable THP")
> Signed-off-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> Cc: Matthew Auld <matthew.auld at intel.com>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Jani Nikula <jani.nikula at linux.intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> Cc: Valtteri Rantala <valtteri.rantala at intel.com>
> Cc: Eero Tamminen <eero.t.tamminen at intel.com>
> Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
> Reviewed-by: Matthew Auld <matthew.auld at intel.com>
Tested-by: Valtteri Rantala <valtteri.rantala at intel.com>

> ---
>  drivers/gpu/drm/i915/i915_gemfs.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gemfs.c
> b/drivers/gpu/drm/i915/i915_gemfs.c
> index e2993857df37..888b7d3f04c3 100644
> --- a/drivers/gpu/drm/i915/i915_gemfs.c
> +++ b/drivers/gpu/drm/i915/i915_gemfs.c
> @@ -52,7 +52,8 @@ int i915_gemfs_init(struct drm_i915_private *i915)
> 
>  	if (has_transparent_hugepage()) {
>  		struct super_block *sb = gemfs->mnt_sb;
> -		char options[] = "huge=within_size";
> +		/* FIXME: Disabled until we get W/A for read BW issue. */
> +		char options[] = "huge=never";
>  		int flags = 0;
>  		int err;
> 
> --
> 2.14.3



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