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

[Joonas Lahtinen]

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>
---
 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