From 604e806074f8f7c5031aeb6d14bb2dbea4d14305 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Fri, 8 Sep 2017 19:16:22 +0100 Subject: [PATCH] drm/i915: Only initialize partially filled pagetables If we know that we will completely fill a pagetable (i.e. we are inserting a complete set of 512 pages), we can skip prefilling that PT with scratch entries. If we have to abort the insertion prior to writing the real entries, we will teardown the pagetable and remove it from the page directory (so that we will restart the allocation next time). We could do similar tricks for the PD and PDP, but the likelihood of a single insertion covering the entire 512 entries diminishes, as do the cycle savings. The saving are even greater (relatively) when we are preallocating page tables for huge pages, as then we never need to fill the page table. Signed-off-by: Chris Wilson Cc: Matthew Auld Cc: Joonas Lahtinen Link: https://patchwork.freedesktop.org/patch/msgid/20170908181622.17791-1-chris@chris-wilson.co.uk Reviewed-by: Matthew Auld --- drivers/gpu/drm/i915/i915_gem_gtt.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c index c33c2f97c814b..33181d6eac3fd 100644 --- a/drivers/gpu/drm/i915/i915_gem_gtt.c +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c @@ -1168,19 +1168,22 @@ static int gen8_ppgtt_alloc_pd(struct i915_address_space *vm, unsigned int pde; gen8_for_each_pde(pt, pd, start, length, pde) { + int count = gen8_pte_count(start, length); + if (pt == vm->scratch_pt) { pt = alloc_pt(vm); if (IS_ERR(pt)) goto unwind; - gen8_initialize_pt(vm, pt); + if (count < GEN8_PTES) + gen8_initialize_pt(vm, pt); gen8_ppgtt_set_pde(vm, pd, pt, pde); pd->used_pdes++; GEM_BUG_ON(pd->used_pdes > I915_PDES); } - pt->used_ptes += gen8_pte_count(start, length); + pt->used_ptes += count; } return 0; -- 2.39.5