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BLI_memarena: support merging memory arenas 

Useful when thread-local storage has it's own memory arena containing
data which is kept after the multi-threaded operation has finished.
This commit is contained in:
Campbell Barton 2021-07-15 14:37:26 +10:00
parent 4be166b6b5
commit 5cd1aaf080
2 changed files with 52 additions and 0 deletions
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2
source/blender/blenlib/BLI_memarena.h
View File

@ -50,6 +50,8 @@ void *BLI_memarena_alloc(struct MemArena *ma, size_t size) ATTR_WARN_UNUSED_RESU
void *BLI_memarena_calloc(struct MemArena *ma, size_t size) ATTR_WARN_UNUSED_RESULT
ATTR_NONNULL(1) ATTR_MALLOC ATTR_ALLOC_SIZE(2);
void BLI_memarena_merge(MemArena *ma_dst, MemArena *ma_src) ATTR_NONNULL(1, 2);
void BLI_memarena_clear(MemArena *ma) ATTR_NONNULL(1);
#ifdef __cplusplus

50
source/blender/blenlib/intern/BLI_memarena.c
View File

@ -45,6 +45,7 @@
# define VALGRIND_CREATE_MEMPOOL(pool, rzB, is_zeroed) UNUSED_VARS(pool, rzB, is_zeroed)
# define VALGRIND_DESTROY_MEMPOOL(pool) UNUSED_VARS(pool)
# define VALGRIND_MEMPOOL_ALLOC(pool, addr, size) UNUSED_VARS(pool, addr, size)
# define VALGRIND_MOVE_MEMPOOL(pool_a, pool_b) UNUSED_VARS(pool_a, pool_b)
#endif
struct MemBuf {
@ -178,6 +179,55 @@ void *BLI_memarena_calloc(MemArena *ma, size_t size)
return ptr;
}
/**
* Transfer ownership of allocated blocks from `ma_src` into `ma_dst`,
* cleaning the contents of `ma_src`.
*
* \note Useful for multi-threaded tasks that need a thread-local #MemArena
* that is kept after the multi-threaded operation is completed.
*/
void BLI_memarena_merge(MemArena *ma_dst, MemArena *ma_src)
{
/* Memory arenas must be compatible. */
BLI_assert(ma_dst != ma_src);
BLI_assert(ma_dst->align == ma_src->align);
BLI_assert(ma_dst->use_calloc == ma_src->use_calloc);
BLI_assert(ma_dst->bufsize == ma_src->bufsize);
if (ma_src->bufs == NULL) {
return;
}
if (UNLIKELY(ma_dst->bufs == NULL)) {
BLI_assert(ma_dst->curbuf == NULL);
ma_dst->bufs = ma_src->bufs;
ma_dst->curbuf = ma_src->curbuf;
ma_dst->cursize = ma_src->cursize;
}
else {
/* Keep the 'ma_dst->curbuf' for simplicity.
* Insert buffers after the first. */
if (ma_dst->bufs->next != NULL) {
/* Loop over `ma_src` instead of `ma_dst` since it's likely the destination is larger
* when used for accumulating from multiple sources. */
struct MemBuf *mb_src = ma_src->bufs;
mb_src = ma_src->bufs;
while (mb_src && mb_src->next) {
mb_src = mb_src->next;
}
mb_src->next = ma_dst->bufs->next;
}
ma_dst->bufs->next = ma_src->bufs;
}
ma_src->bufs = NULL;
ma_src->curbuf = NULL;
ma_src->cursize = 0;
VALGRIND_MOVE_MEMPOOL(ma_src, ma_dst);
VALGRIND_CREATE_MEMPOOL(ma_src, 0, false);
}
/**
* Clear for reuse, avoids re-allocation when an arena may
* otherwise be free'd and recreated.