On 26/09/2018 09:15, Chris Wilson wrote:
Quoting Tvrtko Ursulin (2018-09-26 09:03:53)
From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Partial views are small but there can be many of them, and since the sg
list space for them is allocated pessimistically, we can save some slab by
trimming the unused tail entries.
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
---
On the other hand with the diminishing importance of mmap ggtt do we
expect to see partial views in use these days?
We have over a decade of hw that depends on them, and mesa is still not
entirely rid of them (and there's always i915_dri.so). So partials are
very much sticking around for a long time to come.
---
drivers/gpu/drm/i915/i915_drv.h | 2 ++
drivers/gpu/drm/i915/i915_gem.c | 2 +-
drivers/gpu/drm/i915/i915_gem_gtt.c | 2 ++
3 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 8624b4bdc242..0fe22263aa9b 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2323,6 +2323,8 @@ static inline struct scatterlist *__sg_next(struct scatterlist *sg)
(((__iter).curr += PAGE_SIZE) >= (__iter).max) ? \
(__iter) = __sgt_iter(__sg_next((__iter).sgp), false), 0 : 0)
+bool i915_sg_trim(struct sg_table *orig_st);
+
static inline unsigned int i915_sg_page_sizes(struct scatterlist *sg)
{
unsigned int page_sizes;
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index db9688d14912..7156ddef178b 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2491,7 +2491,7 @@ void __i915_gem_object_put_pages(struct drm_i915_gem_object *obj,
mutex_unlock(&obj->mm.lock);
}
-static bool i915_sg_trim(struct sg_table *orig_st)
+bool i915_sg_trim(struct sg_table *orig_st)
{
struct sg_table new_st;
struct scatterlist *sg, *new_sg;
You can spare me having to move a few lines later if you move this to
i915_scatterlist_utils.c?
To be honest I am feeling optimistic today and said to myself I'd try to
add a proper trim to lib/scatterlist.c. It may take a better part of the
year to merge it :) but the dumb trim is starting to annoy me.
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index f6c7ab413081..1ec721c20581 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -3835,6 +3835,8 @@ intel_partial_pages(const struct i915_ggtt_view *view,
count -= len >> PAGE_SHIFT;
if (count == 0) {
sg_mark_end(sg);
+ i915_sg_trim(st); /* Drop any unused tail entries. */
+
Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
With the move to i915_scatterlist_utils.c and can keep it then?
What do you need the new file for - the error state stuff?
Regards,
Tvrtko
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