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authorKenneth Graunke <[email protected]>2018-04-20 18:45:25 -0700
committerKenneth Graunke <[email protected]>2019-02-21 10:26:06 -0800
commitdbd4770397c6c7bd3f1d9c887504f0972d144be6 (patch)
tree105eee13763853e61140896aee93c15c1022e7ec /src
parent841b3b90032c4a31c98f464bd0cf041da0388f39 (diff)
iris: pull in newer comments
Diffstat (limited to 'src')
-rw-r--r--src/gallium/drivers/iris/iris_bufmgr.c29
1 files changed, 16 insertions, 13 deletions
diff --git a/src/gallium/drivers/iris/iris_bufmgr.c b/src/gallium/drivers/iris/iris_bufmgr.c
index 3c7ce9f5bcf..8919559ea9e 100644
--- a/src/gallium/drivers/iris/iris_bufmgr.c
+++ b/src/gallium/drivers/iris/iris_bufmgr.c
@@ -106,23 +106,26 @@ atomic_add_unless(int *v, int add, int unless)
return c == unless;
}
-/*
- * Idea:
- *
- * Have a bitmap-allocator for each BO cache bucket size. Because bo_alloc
- * rounds up allocations to the bucket size anyway, we can make 1 bit in the
- * bitmap represent N pages of memory, where N = <bucket size / page size>.
- * Allocations and frees always set/unset a single bit. Because ffsll only
- * works on uint64_t, use a tree(?) of those.
+/**
+ * Iris fixed-size bucketing VMA allocator.
*
- * Nodes contain a starting address and a uint64_t bitmap. (pair-of-uint64_t)
- * Bitmap uses 1 for a free block, 0 for in-use.
+ * The BO cache maintains "cache buckets" for buffers of various sizes.
+ * All buffers in a given bucket are identically sized - when allocating,
+ * we always round up to the bucket size. This means that virtually all
+ * allocations are fixed-size; only buffers which are too large to fit in
+ * a bucket can be variably-sized.
*
- * Bucket contains...
+ * We create an allocator for each bucket. Each contains a free-list, where
+ * each node contains a <starting address, 64-bit bitmap> pair. Each bit
+ * represents a bucket-sized block of memory. (At the first level, each
+ * bit corresponds to a page. For the second bucket, bits correspond to
+ * two pages, and so on.) 1 means a block is free, and 0 means it's in-use.
*
- * Dynamic array of nodes. (pointer, two ints)
+ * This makes allocations cheap - any bit of any node will do. We can pick
+ * the head of the list and use ffs() to find a free block. If there are
+ * none, we allocate 64 blocks from a larger allocator - either a bigger
+ * bucketing allocator, or a fallback top-level allocator for large objects.
*/
-
struct vma_bucket_node {
uint64_t start_address;
uint64_t bitmap;