From bbba96931762bcad8a691dfbf8d1520b71831c3a Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Sat, 4 Feb 2017 11:19:13 +0000 Subject: [PATCH] drm: Micro-optimise drm_mm_for_each_node_in_range() As we require valid start/end parameters, we can replace the initial potential NULL with a pointer to the drm_mm.head_node and so reduce the test on every iteration from a NULL + address comparison to just an address comparison. add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-26 (-26) function old new delta i915_gem_evict_for_node 719 693 -26 (No other users outside of the test harness.) Signed-off-by: Chris Wilson Cc: Joonas Lahtinen Reviewed-by: Joonas Lahtinen Signed-off-by: Daniel Vetter Link: http://patchwork.freedesktop.org/patch/msgid/20170204111913.12416-1-chris@chris-wilson.co.uk --- drivers/gpu/drm/drm_mm.c | 2 +- drivers/gpu/drm/selftests/test-drm_mm.c | 10 ++++++---- include/drm/drm_mm.h | 5 ++++- 3 files changed, 11 insertions(+), 6 deletions(-) diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c index 8bfb0b327267..f794089d30ac 100644 --- a/drivers/gpu/drm/drm_mm.c +++ b/drivers/gpu/drm/drm_mm.c @@ -170,7 +170,7 @@ struct drm_mm_node * __drm_mm_interval_first(const struct drm_mm *mm, u64 start, u64 last) { return drm_mm_interval_tree_iter_first((struct rb_root *)&mm->interval_tree, - start, last); + start, last) ?: (struct drm_mm_node *)&mm->head_node; } EXPORT_SYMBOL(__drm_mm_interval_first); diff --git a/drivers/gpu/drm/selftests/test-drm_mm.c b/drivers/gpu/drm/selftests/test-drm_mm.c index 1e71bc182ca9..2958f596081e 100644 --- a/drivers/gpu/drm/selftests/test-drm_mm.c +++ b/drivers/gpu/drm/selftests/test-drm_mm.c @@ -839,16 +839,18 @@ static bool assert_contiguous_in_range(struct drm_mm *mm, n++; } - drm_mm_for_each_node_in_range(node, mm, 0, start) { - if (node) { + if (start > 0) { + node = __drm_mm_interval_first(mm, 0, start - 1); + if (node->allocated) { pr_err("node before start: node=%llx+%llu, start=%llx\n", node->start, node->size, start); return false; } } - drm_mm_for_each_node_in_range(node, mm, end, U64_MAX) { - if (node) { + if (end < U64_MAX) { + node = __drm_mm_interval_first(mm, end, U64_MAX); + if (node->allocated) { pr_err("node after end: node=%llx+%llu, end=%llx\n", node->start, node->size, end); return false; diff --git a/include/drm/drm_mm.h b/include/drm/drm_mm.h index d81b0ba9921f..f262da180117 100644 --- a/include/drm/drm_mm.h +++ b/include/drm/drm_mm.h @@ -459,10 +459,13 @@ __drm_mm_interval_first(const struct drm_mm *mm, u64 start, u64 last); * but using the internal interval tree to accelerate the search for the * starting node, and so not safe against removal of elements. It assumes * that @end is within (or is the upper limit of) the drm_mm allocator. + * If [@start, @end] are beyond the range of the drm_mm, the iterator may walk + * over the special _unallocated_ &drm_mm.head_node, and may even continue + * indefinitely. */ #define drm_mm_for_each_node_in_range(node__, mm__, start__, end__) \ for (node__ = __drm_mm_interval_first((mm__), (start__), (end__)-1); \ - node__ && node__->start < (end__); \ + node__->start < (end__); \ node__ = list_next_entry(node__, node_list)) void drm_mm_scan_init_with_range(struct drm_mm_scan *scan, -- 2.20.1