[Mesa-dev] [PATCH v2 1/4] i965: Add virtual memory allocator infrastructure to brw_bufmgr.
Kenneth Graunke
kenneth at whitecape.org
Mon May 28 04:35:40 UTC 2018
This introduces a new fast virtual memory allocator integrated with our
BO cache bucketing. For larger objects, it falls back to the simple
free-list allocator (util_vma).
This puts the allocators in place but doesn't enable softpin yet.
v2:
(feedback from Chris Wilson)
- Check (bo->kflags & EXEC_OBJECT_PINNED) instead of a global flag
- Avoid vma_free(0ull) on the err_free path.
- Only enable if the kernel says we have full PPGTT support
- Make bucketing allocators more resistant to failing to grow arrays
(feedback from Scott Phillips)
- Don't use node after popping it from the list.
- Avoid undefined behavior in canonicalization by reusing new helper
- Comment updates
(feedback from myself)
- Avoid __vma_alloc vs. vma_alloc by making a zero_high_bits helper
to return a non-canonical address with the high bits zeroed.
---
src/mesa/drivers/dri/i965/brw_bufmgr.c | 291 ++++++++++++++++++++++++-
src/mesa/drivers/dri/i965/brw_bufmgr.h | 2 +
2 files changed, 292 insertions(+), 1 deletion(-)
I plan to land this series this week, barring any major objections.
Scott reviewed it all (from my v1.9 branch), but I wasn't positive
whether some of his reviews still applied...so I figured I'd play it
safe and send it out one more time.
diff --git a/src/mesa/drivers/dri/i965/brw_bufmgr.c b/src/mesa/drivers/dri/i965/brw_bufmgr.c
index 66828f319be..13d32255715 100644
--- a/src/mesa/drivers/dri/i965/brw_bufmgr.c
+++ b/src/mesa/drivers/dri/i965/brw_bufmgr.c
@@ -54,12 +54,15 @@
#endif
#include "common/gen_clflush.h"
#include "common/gen_debug.h"
+#include "common/gen_gem.h"
#include "dev/gen_device_info.h"
#include "libdrm_macros.h"
#include "main/macros.h"
#include "util/macros.h"
#include "util/hash_table.h"
#include "util/list.h"
+#include "util/u_dynarray.h"
+#include "util/vma.h"
#include "brw_bufmgr.h"
#include "brw_context.h"
#include "string.h"
@@ -98,9 +101,41 @@ atomic_add_unless(int *v, int add, int unless)
return c == unless;
}
+/**
+ * i965 fixed-size bucketing VMA allocator.
+ *
+ * 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.
+ *
+ * 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.
+ * The lowest bit in the bitmap is for the first block.
+ *
+ * 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;
+};
+
struct bo_cache_bucket {
+ /** List of cached BOs. */
struct list_head head;
+
+ /** Size of this bucket, in bytes. */
uint64_t size;
+
+ /** List of vma_bucket_nodes. */
+ struct util_dynarray vma_list[BRW_MEMZONE_COUNT];
};
struct brw_bufmgr {
@@ -116,6 +151,8 @@ struct brw_bufmgr {
struct hash_table *name_table;
struct hash_table *handle_table;
+ struct util_vma_heap vma_allocator[BRW_MEMZONE_COUNT];
+
bool has_llc:1;
bool has_mmap_wc:1;
bool bo_reuse:1;
@@ -128,6 +165,17 @@ static int bo_set_tiling_internal(struct brw_bo *bo, uint32_t tiling_mode,
static void bo_free(struct brw_bo *bo);
+static uint64_t
+zero_high_bits(uint64_t addr)
+{
+ /* Un-canonicalize the address, zeroing out the high bits. */
+ return addr & ((1ull << 48) - 1);
+}
+
+static uint64_t vma_alloc(struct brw_bufmgr *bufmgr,
+ enum brw_memory_zone memzone,
+ uint64_t size, uint64_t alignment);
+
static uint32_t
key_hash_uint(const void *key)
{
@@ -222,6 +270,187 @@ bucket_for_size(struct brw_bufmgr *bufmgr, uint64_t size)
&bufmgr->cache_bucket[index] : NULL;
}
+static enum brw_memory_zone
+memzone_for_address(uint64_t address)
+{
+ const uint64_t _4GB = 1ull << 32;
+
+ if (address >= _4GB)
+ return BRW_MEMZONE_OTHER;
+
+ return BRW_MEMZONE_LOW_4G;
+}
+
+static uint64_t
+bucket_vma_alloc(struct brw_bufmgr *bufmgr,
+ struct bo_cache_bucket *bucket,
+ enum brw_memory_zone memzone)
+{
+ struct util_dynarray *vma_list = &bucket->vma_list[memzone];
+ struct vma_bucket_node *node;
+
+ if (vma_list->size == 0) {
+ /* This bucket allocator is out of space - allocate a new block of
+ * memory for 64 blocks from a larger allocator (either a larger
+ * bucket or util_vma).
+ *
+ * We align the address to the node size (64 blocks) so that
+ * bucket_vma_free can easily compute the starting address of this
+ * block by rounding any address we return down to the node size.
+ *
+ * Set the first bit used, and return the start address.
+ */
+ uint64_t node_size = 64ull * bucket->size;
+ node = util_dynarray_grow(vma_list, sizeof(struct vma_bucket_node));
+
+ if (unlikely(!node))
+ return 0ull;
+
+ uint64_t addr = vma_alloc(bufmgr, memzone, node_size, node_size);
+ node->start_address = zero_high_bits(addr);
+ node->bitmap = ~1ull;
+ return node->start_address;
+ }
+
+ /* Pick any bit from any node - they're all the right size and free. */
+ node = util_dynarray_top_ptr(vma_list, struct vma_bucket_node);
+ int bit = ffsll(node->bitmap) - 1;
+ assert(bit >= 0 && bit <= 63);
+
+ /* Reserve the memory by clearing the bit. */
+ assert((node->bitmap & (1ull << bit)) != 0ull);
+ node->bitmap &= ~(1ull << bit);
+
+ uint64_t addr = node->start_address + bit * bucket->size;
+
+ /* If this node is now completely full, remove it from the free list. */
+ if (node->bitmap == 0ull) {
+ (void) util_dynarray_pop(vma_list, struct vma_bucket_node);
+ }
+
+ return addr;
+}
+
+static void
+bucket_vma_free(struct bo_cache_bucket *bucket, uint64_t address)
+{
+ enum brw_memory_zone memzone = memzone_for_address(address);
+ struct util_dynarray *vma_list = &bucket->vma_list[memzone];
+ const uint64_t node_bytes = 64ull * bucket->size;
+ struct vma_bucket_node *node = NULL;
+
+ /* bucket_vma_alloc allocates 64 blocks at a time, and aligns it to
+ * that 64 block size. So, we can round down to get the starting address.
+ */
+ uint64_t start = (address / node_bytes) * node_bytes;
+
+ /* Dividing the offset from start by bucket size gives us the bit index. */
+ int bit = (address - start) / bucket->size;
+
+ assert(start + bit * bucket->size == address);
+
+ util_dynarray_foreach(vma_list, struct vma_bucket_node, cur) {
+ if (cur->start_address == start) {
+ node = cur;
+ break;
+ }
+ }
+
+ if (!node) {
+ /* No node - the whole group of 64 blocks must have been in-use. */
+ node = util_dynarray_grow(vma_list, sizeof(struct vma_bucket_node));
+
+ if (unlikely(!node))
+ return; /* bogus, leaks some GPU VMA, but nothing we can do... */
+
+ node->start_address = start;
+ node->bitmap = 0ull;
+ }
+
+ /* Set the bit to return the memory. */
+ assert((node->bitmap & (1ull << bit)) == 0ull);
+ node->bitmap |= 1ull << bit;
+
+ /* The block might be entirely free now, and if so, we could return it
+ * to the larger allocator. But we may as well hang on to it, in case
+ * we get more allocations at this block size.
+ */
+}
+
+static struct bo_cache_bucket *
+get_bucket_allocator(struct brw_bufmgr *bufmgr, uint64_t size)
+{
+ /* Skip using the bucket allocator for very large sizes, as it allocates
+ * 64 of them and this can balloon rather quickly.
+ */
+ if (size > 1024 * PAGE_SIZE)
+ return NULL;
+
+ struct bo_cache_bucket *bucket = bucket_for_size(bufmgr, size);
+
+ if (bucket && bucket->size == size)
+ return bucket;
+
+ return NULL;
+}
+
+/**
+ * Allocate a section of virtual memory for a buffer, assigning an address.
+ *
+ * This uses either the bucket allocator for the given size, or the large
+ * object allocator (util_vma).
+ */
+static uint64_t
+vma_alloc(struct brw_bufmgr *bufmgr,
+ enum brw_memory_zone memzone,
+ uint64_t size,
+ uint64_t alignment)
+{
+ /* Without softpin support, we let the kernel assign addresses. */
+ assert(brw_using_softpin(bufmgr));
+
+ struct bo_cache_bucket *bucket = get_bucket_allocator(bufmgr, size);
+ uint64_t addr;
+
+ if (bucket) {
+ addr = bucket_vma_alloc(bufmgr, bucket, memzone);
+ } else {
+ addr = util_vma_heap_alloc(&bufmgr->vma_allocator[memzone], size,
+ alignment);
+ }
+
+ assert((addr >> 48ull) == 0);
+ assert((addr % alignment) == 0);
+
+ return gen_canonical_address(addr);
+}
+
+/**
+ * Free a virtual memory area, allowing the address to be reused.
+ */
+static void
+vma_free(struct brw_bufmgr *bufmgr,
+ uint64_t address,
+ uint64_t size)
+{
+ assert(brw_using_softpin(bufmgr));
+
+ /* Un-canonicalize the address. */
+ address = zero_high_bits(address);
+
+ if (address == 0ull)
+ return;
+
+ struct bo_cache_bucket *bucket = get_bucket_allocator(bufmgr, size);
+
+ if (bucket) {
+ bucket_vma_free(bucket, address);
+ } else {
+ enum brw_memory_zone memzone = memzone_for_address(address);
+ util_vma_heap_free(&bufmgr->vma_allocator[memzone], address, size);
+ }
+}
+
int
brw_bo_busy(struct brw_bo *bo)
{
@@ -360,7 +589,16 @@ retry:
}
}
- if (!alloc_from_cache) {
+ if (alloc_from_cache) {
+ /* If the cache BO isn't in the right memory zone, free the old
+ * memory and assign it a new address.
+ */
+ if ((bo->kflags & EXEC_OBJECT_PINNED) &&
+ memzone != memzone_for_address(bo->gtt_offset)) {
+ vma_free(bufmgr, bo->gtt_offset, bo->size);
+ bo->gtt_offset = 0ull;
+ }
+ } else {
bo = calloc(1, sizeof(*bo));
if (!bo)
goto err;
@@ -411,6 +649,13 @@ retry:
bo->index = -1;
bo->kflags = bufmgr->initial_kflags;
+ if ((bo->kflags & EXEC_OBJECT_PINNED) && bo->gtt_offset == 0ull) {
+ bo->gtt_offset = vma_alloc(bufmgr, memzone, bo->size, 1);
+
+ if (bo->gtt_offset == 0ull)
+ goto err_free;
+ }
+
mtx_unlock(&bufmgr->lock);
DBG("bo_create: buf %d (%s) %llub\n", bo->gem_handle, bo->name,
@@ -545,6 +790,9 @@ brw_bo_gem_create_from_name(struct brw_bufmgr *bufmgr,
bo->external = true;
bo->kflags = bufmgr->initial_kflags;
+ if (bo->kflags & EXEC_OBJECT_PINNED)
+ bo->gtt_offset = vma_alloc(bufmgr, BRW_MEMZONE_OTHER, bo->size, 1);
+
_mesa_hash_table_insert(bufmgr->handle_table, &bo->gem_handle, bo);
_mesa_hash_table_insert(bufmgr->name_table, &bo->global_name, bo);
@@ -605,6 +853,10 @@ bo_free(struct brw_bo *bo)
DBG("DRM_IOCTL_GEM_CLOSE %d failed (%s): %s\n",
bo->gem_handle, bo->name, strerror(errno));
}
+
+ if (bo->kflags & EXEC_OBJECT_PINNED)
+ vma_free(bo->bufmgr, bo->gtt_offset, bo->size);
+
free(bo);
}
@@ -1063,11 +1315,22 @@ brw_bufmgr_destroy(struct brw_bufmgr *bufmgr)
bo_free(bo);
}
+
+ if (brw_using_softpin(bufmgr)) {
+ for (int i = 0; i < BRW_MEMZONE_COUNT; i++)
+ util_dynarray_fini(&bucket->vma_list[i]);
+ }
}
_mesa_hash_table_destroy(bufmgr->name_table, NULL);
_mesa_hash_table_destroy(bufmgr->handle_table, NULL);
+ if (brw_using_softpin(bufmgr)) {
+ for (int z = 0; z < BRW_MEMZONE_COUNT; z++) {
+ util_vma_heap_finish(&bufmgr->vma_allocator[z]);
+ }
+ }
+
free(bufmgr);
}
@@ -1165,6 +1428,11 @@ brw_bo_gem_create_from_prime_internal(struct brw_bufmgr *bufmgr, int prime_fd,
bo->external = true;
bo->kflags = bufmgr->initial_kflags;
+ if (bo->kflags & EXEC_OBJECT_PINNED) {
+ assert(bo->size > 0);
+ bo->gtt_offset = vma_alloc(bufmgr, BRW_MEMZONE_OTHER, bo->size, 1);
+ }
+
if (tiling_mode < 0) {
struct drm_i915_gem_get_tiling get_tiling = { .handle = bo->gem_handle };
if (drmIoctl(bufmgr->fd, DRM_IOCTL_I915_GEM_GET_TILING, &get_tiling))
@@ -1291,6 +1559,10 @@ add_bucket(struct brw_bufmgr *bufmgr, int size)
assert(i < ARRAY_SIZE(bufmgr->cache_bucket));
list_inithead(&bufmgr->cache_bucket[i].head);
+ if (brw_using_softpin(bufmgr)) {
+ for (int z = 0; z < BRW_MEMZONE_COUNT; z++)
+ util_dynarray_init(&bufmgr->cache_bucket[i].vma_list[z], NULL);
+ }
bufmgr->cache_bucket[i].size = size;
bufmgr->num_buckets++;
@@ -1408,6 +1680,12 @@ gem_context_getparam(int fd, uint32_t context, uint64_t param, uint64_t *value)
return 0;
}
+bool
+brw_using_softpin(struct brw_bufmgr *bufmgr)
+{
+ return bufmgr->initial_kflags & EXEC_OBJECT_PINNED;
+}
+
/**
* Initializes the GEM buffer manager, which uses the kernel to allocate, map,
* and manage map buffer objections.
@@ -1450,6 +1728,17 @@ brw_bufmgr_init(struct gen_device_info *devinfo, int fd)
if (devinfo->gen >= 8 && gtt_size > _4GB) {
bufmgr->initial_kflags |= EXEC_OBJECT_SUPPORTS_48B_ADDRESS;
+
+ /* Allocate VMA in userspace if we have softpin and full PPGTT. */
+ if (false && gem_param(fd, I915_PARAM_HAS_EXEC_SOFTPIN) > 0 &&
+ gem_param(fd, I915_PARAM_HAS_ALIASING_PPGTT) > 1) {
+ bufmgr->initial_kflags |= EXEC_OBJECT_PINNED;
+
+ util_vma_heap_init(&bufmgr->vma_allocator[BRW_MEMZONE_LOW_4G],
+ 4096, _4GB);
+ util_vma_heap_init(&bufmgr->vma_allocator[BRW_MEMZONE_OTHER],
+ 1 * _4GB, gtt_size - 1 * _4GB);
+ }
}
init_cache_buckets(bufmgr);
diff --git a/src/mesa/drivers/dri/i965/brw_bufmgr.h b/src/mesa/drivers/dri/i965/brw_bufmgr.h
index 9ad129744b2..8cdf944e3da 100644
--- a/src/mesa/drivers/dri/i965/brw_bufmgr.h
+++ b/src/mesa/drivers/dri/i965/brw_bufmgr.h
@@ -370,6 +370,8 @@ uint32_t brw_bo_export_gem_handle(struct brw_bo *bo);
int brw_reg_read(struct brw_bufmgr *bufmgr, uint32_t offset,
uint64_t *result);
+bool brw_using_softpin(struct brw_bufmgr *bufmgr);
+
/** @{ */
#if defined(__cplusplus)
--
2.17.0
More information about the mesa-dev
mailing list