* @file
* S-lab pool implementation.
*
+ * @sa http://en.wikipedia.org/wiki/Slab_allocation
+ *
* @author Thomas Hellstrom <thomas-at-tungstengraphics-dot-com>
* @author Jose Fonseca <jrfonseca@tungstengraphics.com>
*/
struct pb_slab;
+
+/**
+ * Buffer in a slab.
+ *
+ * Sub-allocation of a contiguous buffer.
+ */
struct pb_slab_buffer
{
struct pb_buffer base;
struct pb_slab *slab;
+
struct list_head head;
+
unsigned mapCount;
+
+ /** Offset relative to the start of the slab buffer. */
size_t start;
+
+ /** Use when validating, to signal that all mappings are finished */
+ /* TODO: Actually validation does not reach this stage yet */
pipe_condvar event;
};
+
+/**
+ * Slab -- a contiguous piece of memory.
+ */
struct pb_slab
{
struct list_head head;
struct list_head freeBuffers;
size_t numBuffers;
size_t numFree;
+
struct pb_slab_buffer *buffers;
struct pb_slab_manager *mgr;
+ /** Buffer from the provider */
struct pb_buffer *bo;
+
void *virtual;
};
+
+/**
+ * It adds/removes slabs as needed in order to meet the allocation/destruction
+ * of individual buffers.
+ */
struct pb_slab_manager
{
struct pb_manager base;
+ /** From where we get our buffers */
struct pb_manager *provider;
+
+ /** Size of the buffers we hand on downstream */
size_t bufSize;
+
+ /** Size of the buffers we request upstream */
size_t slabSize;
+
+ /**
+ * Alignment, usage to be used to allocate the slab buffers.
+ *
+ * We can only provide buffers which are consistent (in alignment, usage)
+ * with this description.
+ */
struct pb_desc desc;
+ /**
+ * Partial slabs
+ *
+ * Full slabs are not stored in any list. Empty slabs are destroyed
+ * immediatly.
+ */
struct list_head slabs;
- struct list_head freeSlabs;
pipe_mutex mutex;
};
+
/**
+ * Wrapper around several slabs, therefore capable of handling buffers of
+ * multiple sizes.
+ *
+ * This buffer manager just dispatches buffer allocations to the appropriate slab
+ * manager, according to the requested buffer size, or by passes the slab
+ * managers altogether for even greater sizes.
+ *
* The data of this structure remains constant after
* initialization and thus needs no mutex protection.
*/
struct pb_manager base;
struct pb_manager *provider;
+
size_t minBufSize;
size_t maxBufSize;
+
+ /** @sa pb_slab_manager::desc */
struct pb_desc desc;
unsigned numBuckets;
size_t *bucketSizes;
+
+ /** Array of pb_slab_manager, one for each bucket size */
struct pb_manager **buckets;
};
if (slab->head.next == &slab->head)
LIST_ADDTAIL(&slab->head, &mgr->slabs);
+ /* If the slab becomes totally empty, free it */
if (slab->numFree == slab->numBuffers) {
list = &slab->head;
- LIST_DEL(list);
- LIST_ADDTAIL(list, &mgr->freeSlabs);
+ LIST_DELINIT(list);
+ pb_reference(&slab->bo, NULL);
+ FREE(slab->buffers);
+ FREE(slab);
}
- if (mgr->slabs.next == &mgr->slabs || slab->numFree
- != slab->numBuffers) {
-
- struct list_head *next;
-
- for (list = mgr->freeSlabs.next, next = list->next; list
- != &mgr->freeSlabs; list = next, next = list->next) {
-
- slab = LIST_ENTRY(struct pb_slab, list, head);
-
- LIST_DELINIT(list);
- pb_reference(&slab->bo, NULL);
- FREE(slab->buffers);
- FREE(slab);
- }
- }
-
pipe_mutex_unlock(mgr->mutex);
}
};
+/**
+ * Create a new slab.
+ *
+ * Called when we ran out of free slabs.
+ */
static enum pipe_error
pb_slab_create(struct pb_slab_manager *mgr)
{
if (!slab)
return PIPE_ERROR_OUT_OF_MEMORY;
- /*
- * FIXME: We should perhaps allow some variation in slabsize in order
- * to efficiently reuse slabs.
- */
-
slab->bo = mgr->provider->create_buffer(mgr->provider, mgr->slabSize, &mgr->desc);
if(!slab->bo) {
ret = PIPE_ERROR_OUT_OF_MEMORY;
goto out_err0;
}
+ /* Note down the slab virtual address. All mappings are accessed directly
+ * through this address so it is required that the buffer is pinned. */
slab->virtual = pb_map(slab->bo,
PIPE_BUFFER_USAGE_CPU_READ |
PIPE_BUFFER_USAGE_CPU_WRITE);
ret = PIPE_ERROR_OUT_OF_MEMORY;
goto out_err1;
}
-
pb_unmap(slab->bo);
numBuffers = slab->bo->base.size / mgr->bufSize;
buf++;
}
+ /* Add this slab to the list of partial slabs */
LIST_ADDTAIL(&slab->head, &mgr->slabs);
return PIPE_OK;
return NULL;
pipe_mutex_lock(mgr->mutex);
+
+ /* Create a new slab, if we run out of partial slabs */
if (mgr->slabs.next == &mgr->slabs) {
(void) pb_slab_create(mgr);
if (mgr->slabs.next == &mgr->slabs) {
return NULL;
}
}
+
+ /* Allocate the buffer from a partial (or just created) slab */
list = mgr->slabs.next;
slab = LIST_ENTRY(struct pb_slab, list, head);
+
+ /* If totally full remove from the partial slab list */
if (--slab->numFree == 0)
LIST_DELINIT(list);
mgr->desc = *desc;
LIST_INITHEAD(&mgr->slabs);
- LIST_INITHEAD(&mgr->freeSlabs);
pipe_mutex_init(mgr->mutex);
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