This is a note to let you know that I've just added the patch titled
drm/i915: Use MLC (l3$) for context objects
to the 3.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drm-i915-use-mlc-l3-for-context-objects.patch
and it can be found in the queue-3.8 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 4615d4c9e27eda42c3e965f208a4b4065841498c Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Date: Mon, 8 Apr 2013 14:28:40 +0100
Subject: drm/i915: Use MLC (l3$) for context objects
From: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
commit 4615d4c9e27eda42c3e965f208a4b4065841498c upstream.
Enabling context support increases SwapBuffers latency by about 20%
(measured on an i7-3720qm). We can offset that loss slightly by enabling
faster caching for the contexts. As they are not backed by any
particular cache (such as the sampler or render caches) our only option
is to select the generic mid-level cache. This reduces the latency of
the swap by about 5%.
Oddly this effect can be observed running smokin-guns on IVB at
1280x1024:
Using BLT copies for swaps: 151.67 fps
Using Render copies for swaps (unpatched): 141.70 fps
With contexts disabled: 150.23 fps
With contexts in L3$: 150.77 fps
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Ben Widawsky <ben@xxxxxxxxxxxx>
Cc: Kenneth Graunke <kenneth@xxxxxxxxxxxxx>
Reviewed-by: Kenneth Graunke <kenneth@xxxxxxxxxxxxx>
Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/i915_gem_context.c | 7 +++++++
1 file changed, 7 insertions(+)
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -157,6 +157,13 @@ create_hw_context(struct drm_device *dev
return ERR_PTR(-ENOMEM);
}
+ if (INTEL_INFO(dev)->gen >= 7) {
+ ret = i915_gem_object_set_cache_level(ctx->obj,
+ I915_CACHE_LLC_MLC);
+ if (ret)
+ goto err_out;
+ }
+
/* The ring associated with the context object is handled by the normal
* object tracking code. We give an initial ring value simple to pass an
* assertion in the context switch code.
Patches currently in stable-queue which might be from chris@xxxxxxxxxxxxxxxxxx are
queue-3.8/drm-i915-fix-detection-of-base-of-stolen-memory.patch
queue-3.8/drm-i915-use-mlc-l3-for-context-objects.patch
queue-3.8/drm-i915-workaround-incoherence-between-fences-and-llc-across-multiple-cpus.patch
queue-3.8/drm-i915-fix-sdvo-connector-get_hw_state-function.patch
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