From 4846bf0ca8cb4304dde6140eff33a92b3fe8ef24 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Fri, 9 Jun 2017 12:03:46 +0100 Subject: [PATCH] drm/i915: Encourage our shrinker more when our shmemfs allocations fails Commit 24f8e00a8a2e ("drm/i915: Prefer to report ENOMEM rather than incur the oom for gfx allocations") made the bold decision to try and avoid the oomkiller by reporting -ENOMEM to userspace if our allocation failed after attempting to free enough buffer objects. In short, it appears we were giving up too easily (even before we start wondering if one pass of reclaim is as strong as we would like). Part of the problem is that if we only shrink just enough pages for our expected allocation, the likelihood of those pages becoming available to us is less than 100% To counter-act that we ask for twice the number of pages to be made available. Furthermore, we allow the shrinker to pull pages from the active list in later passes. v2: Be a little more cautious in paging out gfx buffers, and leave that to a more balanced approach from shrink_slab(). Important when combined with "drm/i915: Start writeback from the shrinker" as anything shrunk is immediately swapped out and so should be more conservative. Fixes: 24f8e00a8a2e ("drm/i915: Prefer to report ENOMEM rather than incur the oom for gfx allocations") Signed-off-by: Chris Wilson Cc: Mika Kuoppala Cc: Joonas Lahtinen Cc: Daniel Vetter Reviewed-by: Joonas Lahtinen Link: http://patchwork.freedesktop.org/patch/msgid/20170609110350.1767-1-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/i915_gem.c | 50 +++++++++++++++++++-------------- 1 file changed, 29 insertions(+), 21 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index aff449807399..ca61a0be1458 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -2337,8 +2337,8 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj) struct page *page; unsigned long last_pfn = 0; /* suppress gcc warning */ unsigned int max_segment; + gfp_t noreclaim; int ret; - gfp_t gfp; /* Assert that the object is not currently in any GPU domain. As it * wasn't in the GTT, there shouldn't be any way it could have been in @@ -2367,22 +2367,31 @@ rebuild_st: * Fail silently without starting the shrinker */ mapping = obj->base.filp->f_mapping; - gfp = mapping_gfp_constraint(mapping, ~(__GFP_IO | __GFP_RECLAIM)); - gfp |= __GFP_NORETRY | __GFP_NOWARN; + noreclaim = mapping_gfp_constraint(mapping, + ~(__GFP_IO | __GFP_RECLAIM)); + noreclaim |= __GFP_NORETRY | __GFP_NOWARN; + sg = st->sgl; st->nents = 0; for (i = 0; i < page_count; i++) { - page = shmem_read_mapping_page_gfp(mapping, i, gfp); - if (unlikely(IS_ERR(page))) { - i915_gem_shrink(dev_priv, - page_count, - I915_SHRINK_BOUND | - I915_SHRINK_UNBOUND | - I915_SHRINK_PURGEABLE); + const unsigned int shrink[] = { + I915_SHRINK_BOUND | I915_SHRINK_UNBOUND | I915_SHRINK_PURGEABLE, + 0, + }, *s = shrink; + gfp_t gfp = noreclaim; + + do { page = shmem_read_mapping_page_gfp(mapping, i, gfp); - } - if (unlikely(IS_ERR(page))) { - gfp_t reclaim; + if (likely(!IS_ERR(page))) + break; + + if (!*s) { + ret = PTR_ERR(page); + goto err_sg; + } + + i915_gem_shrink(dev_priv, 2 * page_count, *s++); + cond_resched(); /* We've tried hard to allocate the memory by reaping * our own buffer, now let the real VM do its job and @@ -2392,15 +2401,13 @@ rebuild_st: * defer the oom here by reporting the ENOMEM back * to userspace. */ - reclaim = mapping_gfp_mask(mapping); - reclaim |= __GFP_NORETRY; /* reclaim, but no oom */ - - page = shmem_read_mapping_page_gfp(mapping, i, reclaim); - if (IS_ERR(page)) { - ret = PTR_ERR(page); - goto err_sg; + if (!*s) { + /* reclaim and warn, but no oom */ + gfp = mapping_gfp_mask(mapping); + gfp |= __GFP_NORETRY; } - } + } while (1); + if (!i || sg->length >= max_segment || page_to_pfn(page) != last_pfn + 1) { @@ -4285,6 +4292,7 @@ i915_gem_object_create(struct drm_i915_private *dev_priv, u64 size) mapping = obj->base.filp->f_mapping; mapping_set_gfp_mask(mapping, mask); + GEM_BUG_ON(!(mapping_gfp_mask(mapping) & __GFP_RECLAIM)); i915_gem_object_init(obj, &i915_gem_object_ops); -- 2.30.2