summaryrefslogtreecommitdiffstats
path: root/drivers/gpu
diff options
context:
space:
mode:
authorDave Gordon <david.s.gordon@intel.com>2016-05-20 11:54:07 +0100
committerChris Wilson <chris@chris-wilson.co.uk>2016-05-20 13:43:00 +0100
commit63d15326168d54cfef082f6899c86f8260db4037 (patch)
tree572c3a0e87f9f1b1c4ec0a551d8e5518f2893317 /drivers/gpu
parent85d1225ec066b2ef46fbd0ed1bae78ae1f3e6c91 (diff)
downloadblackbird-op-linux-63d15326168d54cfef082f6899c86f8260db4037.tar.gz
blackbird-op-linux-63d15326168d54cfef082f6899c86f8260db4037.zip
drm/i915: Inline sg_next() for the optimised SGL iterator
Avoiding the out-of-line call to sg_next() reduces the kernel execution overhead by 10% in some workloads (for example the Unreal Engine 4 demo Atlantis on 2GiB GTTs) which are dominated by the cost of inserting PTEs due to texture thrashing. We can demonstrate this in a microbenchmark that forces us to rebind the object on every execbuf, where we can measure a 25% improvement, in the time required to execute an execbuf requiring a texture to be rebound, for inlining the sg_next() for large texture sizes. Benchmark: igt/benchmarks/gem_exec_fault Benchmark: igt/benchmarks/gem_exec_trace/Atlantis Signed-off-by: Dave Gordon <david.s.gordon@intel.com> Cc: Chris Wilson <chris@chris-wilson.co.uk> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Link: http://patchwork.freedesktop.org/patch/msgid/1463741647-15666-5-git-send-email-chris@chris-wilson.co.uk
Diffstat (limited to 'drivers/gpu')
-rw-r--r--drivers/gpu/drm/i915/i915_drv.h23
1 files changed, 21 insertions, 2 deletions
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 63ff5fa2b2bd..e2abd9eb352b 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2278,6 +2278,25 @@ static __always_inline struct sgt_iter {
}
/**
+ * __sg_next - return the next scatterlist entry in a list
+ * @sg: The current sg entry
+ *
+ * Description:
+ * If the entry is the last, return NULL; otherwise, step to the next
+ * element in the array (@sg@+1). If that's a chain pointer, follow it;
+ * otherwise just return the pointer to the current element.
+ **/
+static inline struct scatterlist *__sg_next(struct scatterlist *sg)
+{
+#ifdef CONFIG_DEBUG_SG
+ BUG_ON(sg->sg_magic != SG_MAGIC);
+#endif
+ return sg_is_last(sg) ? NULL :
+ likely(!sg_is_chain(++sg)) ? sg :
+ sg_chain_ptr(sg);
+}
+
+/**
* for_each_sgt_dma - iterate over the DMA addresses of the given sg_table
* @__dmap: DMA address (output)
* @__iter: 'struct sgt_iter' (iterator state, internal)
@@ -2287,7 +2306,7 @@ static __always_inline struct sgt_iter {
for ((__iter) = __sgt_iter((__sgt)->sgl, true); \
((__dmap) = (__iter).dma + (__iter).curr); \
(((__iter).curr += PAGE_SIZE) < (__iter).max) || \
- ((__iter) = __sgt_iter(sg_next((__iter).sgp), true), 0))
+ ((__iter) = __sgt_iter(__sg_next((__iter).sgp), true), 0))
/**
* for_each_sgt_page - iterate over the pages of the given sg_table
@@ -2300,7 +2319,7 @@ static __always_inline struct sgt_iter {
((__pp) = (__iter).pfn == 0 ? NULL : \
pfn_to_page((__iter).pfn + ((__iter).curr >> PAGE_SHIFT))); \
(((__iter).curr += PAGE_SIZE) < (__iter).max) || \
- ((__iter) = __sgt_iter(sg_next((__iter).sgp), false), 0))
+ ((__iter) = __sgt_iter(__sg_next((__iter).sgp), false), 0))
/**
* Request queue structure.
OpenPOWER on IntegriCloud