On 12/14/2017 04:38 PM, Olivier MATZ wrote:
On Fri, Nov 24, 2017 at 04:06:28PM +0000, Andrew Rybchenko wrote:
From: "Artem V. Andreev" <artem.andr...@oktetlabs.ru>
The manager provides a way to allocate physically and virtually
contiguous set of objects.
Note: due to the way objects are organized in the bucket manager,
the get_avail_count may return less objects than were enqueued.
That breaks the expectation of mempool and mempool_perf tests.
To me, this can be problematic. The driver should respect the
API, or it will trigger hard-to-debug issues in applications. Can't
this be fixed in some way or another?
As I understand there is no requirements on how fast get_count
works. If so, it is doable and we'll fix it in RFCv2.
[...]
--- a/config/common_base
+++ b/config/common_base
@@ -608,6 +608,8 @@ CONFIG_RTE_LIBRTE_MEMPOOL_DEBUG=n
#
# Compile Mempool drivers
#
+CONFIG_RTE_DRIVER_MEMPOOL_BUCKET=y
+CONFIG_RTE_DRIVER_MEMPOOL_BUCKET_SIZE_KB=32
CONFIG_RTE_DRIVER_MEMPOOL_RING=y
CONFIG_RTE_DRIVER_MEMPOOL_STACK=y
Why 32KB?
Why not more, or less?
Can it be a runtime parameter?
I guess it won't work with too large objects.
We have no good understanding of how driver-specific parameters
should be passed on mempool creation. We've simply kept it for
future since it looks like separate task.
If you have ideas, please, share - we'll be thankful.
[...]
+struct bucket_data {
+ unsigned int header_size;
+ unsigned int chunk_size;
+ unsigned int bucket_size;
+ uintptr_t bucket_page_mask;
+ struct rte_ring *shared_bucket_ring;
+ struct bucket_stack *buckets[RTE_MAX_LCORE];
+ /*
+ * Multi-producer single-consumer ring to hold objects that are
+ * returned to the mempool at a different lcore than initially
+ * dequeued
+ */
+ struct rte_ring *adoption_buffer_rings[RTE_MAX_LCORE];
+ struct rte_ring *shared_orphan_ring;
+ struct rte_mempool *pool;
+
+};
I'm seeing per-core structures. Will it work on non-dataplane cores?
For instance, if a control thread wants to allocate a mbuf?
May be I don't understand something. Does the control thread has
valid rte_lcore_id()?
If possible, these fields should be more documented (or just renamed).
For instance, I suggest chunk_size could be called obj_per_bucket, which
better described the content of the field.
Thanks, we'll do.
[...]
+static int
+bucket_enqueue_single(struct bucket_data *data, void *obj)
+{
+ int rc = 0;
+ uintptr_t addr = (uintptr_t)obj;
+ struct bucket_header *hdr;
+ unsigned int lcore_id = rte_lcore_id();
+
+ addr &= data->bucket_page_mask;
+ hdr = (struct bucket_header *)addr;
+
+ if (likely(hdr->lcore_id == lcore_id)) {
+ if (hdr->fill_cnt < data->bucket_size - 1) {
+ hdr->fill_cnt++;
+ } else {
+ hdr->fill_cnt = 0;
+ /* Stack is big enough to put all buckets */
+ bucket_stack_push(data->buckets[lcore_id], hdr);
+ }
+ } else if (hdr->lcore_id != LCORE_ID_ANY) {
+ struct rte_ring *adopt_ring =
+ data->adoption_buffer_rings[hdr->lcore_id];
+
+ rc = rte_ring_enqueue(adopt_ring, obj);
+ /* Ring is big enough to put all objects */
+ RTE_ASSERT(rc == 0);
+ } else if (hdr->fill_cnt < data->bucket_size - 1) {
+ hdr->fill_cnt++;
+ } else {
+ hdr->fill_cnt = 0;
+ rc = rte_ring_enqueue(data->shared_bucket_ring, hdr);
+ /* Ring is big enough to put all buckets */
+ RTE_ASSERT(rc == 0);
+ }
+
+ return rc;
+}
[...]
+static int
+bucket_dequeue_buckets(struct bucket_data *data, void **obj_table,
+ unsigned int n_buckets)
+{
+ struct bucket_stack *cur_stack = data->buckets[rte_lcore_id()];
+ unsigned int n_buckets_from_stack = RTE_MIN(n_buckets, cur_stack->top);
+ void **obj_table_base = obj_table;
+
+ n_buckets -= n_buckets_from_stack;
+ while (n_buckets_from_stack-- > 0) {
+ void *obj = bucket_stack_pop_unsafe(cur_stack);
+
+ obj_table = bucket_fill_obj_table(data, &obj, obj_table,
+ data->bucket_size);
+ }
+ while (n_buckets-- > 0) {
+ struct bucket_header *hdr;
+
+ if (unlikely(rte_ring_dequeue(data->shared_bucket_ring,
+ (void **)&hdr) != 0)) {
+ /* Return the already-dequeued buffers
+ * back to the mempool
+ */
+ bucket_enqueue(data->pool, obj_table_base,
+ obj_table - obj_table_base);
+ rte_errno = ENOBUFS;
+ return -rte_errno;
+ }
+ hdr->lcore_id = rte_lcore_id();
+ obj_table = bucket_fill_obj_table(data, (void **)&hdr,
+ obj_table, data->bucket_size);
+ }
+
+ return 0;
+}
[...]
+static int
+bucket_dequeue(struct rte_mempool *mp, void **obj_table, unsigned int n)
+{
+ struct bucket_data *data = mp->pool_data;
+ unsigned int n_buckets = n / data->bucket_size;
+ unsigned int n_orphans = n - n_buckets * data->bucket_size;
+ int rc = 0;
+
+ bucket_adopt_orphans(data);
+
+ if (unlikely(n_orphans > 0)) {
+ rc = bucket_dequeue_orphans(data, obj_table +
+ (n_buckets * data->bucket_size),
+ n_orphans);
+ if (rc != 0)
+ return rc;
+ }
+
+ if (likely(n_buckets > 0)) {
+ rc = bucket_dequeue_buckets(data, obj_table, n_buckets);
+ if (unlikely(rc != 0) && n_orphans > 0) {
+ rte_ring_enqueue_bulk(data->shared_orphan_ring,
+ obj_table + (n_buckets *
+ data->bucket_size),
+ n_orphans, NULL);
+ }
+ }
+
+ return rc;
+}
If my understanding is correct, at initialization, all full buckets will
go to the data->shared_bucket_ring ring, with lcore_id == ANY (this is
done in register_mem).
(note: I feel 'data' is not an ideal name for bucket_data)
Yes, agree. We'll rename it. It is really too generic.
If the core 0 allocates all the mbufs, and then frees them all, they
will be stored in the per-core stack, with hdr->lcoreid == 0. Is it
right?
Right.
If yes, can core 1 allocate a mbuf after that?
We'll add threshold for per-core stack. If it is exceeded, buckets will be
flushed into shared ring.
+static unsigned int
+bucket_get_count(const struct rte_mempool *mp)
+{
+ const struct bucket_data *data = mp->pool_data;
+ const struct bucket_stack *local_bucket_stack =
+ data->buckets[rte_lcore_id()];
+
+ return data->bucket_size * local_bucket_stack->top +
+ data->bucket_size * rte_ring_count(data->shared_bucket_ring) +
+ rte_ring_count(data->shared_orphan_ring);
+}
It looks that get_count only rely on the current core stack usage
and ignore the other core stacks.
We'll fix it to provide more accurate return value which is required
to pass self-test and make it usable for debugging.
[...]
+static int
+bucket_register_memory_area(__rte_unused const struct rte_mempool *mp,
+ char *vaddr, __rte_unused phys_addr_t paddr,
+ size_t len)
+{
+ /* mp->pool_data may be still uninitialized at this point */
+ unsigned int chunk_size = mp->header_size + mp->elt_size +
+ mp->trailer_size;
+ unsigned int bucket_mem_size =
+ (BUCKET_MEM_SIZE / chunk_size) * chunk_size;
+ unsigned int bucket_page_sz = rte_align32pow2(bucket_mem_size);
+ uintptr_t align;
+ char *iter;
+
+ align = RTE_PTR_ALIGN_CEIL(vaddr, bucket_page_sz) - vaddr;
+
+ for (iter = vaddr + align; iter < vaddr + len; iter += bucket_page_sz) {
+ /* librte_mempool uses the header part for its own bookkeeping,
+ * but the librte_mempool's object header is adjacent to the
+ * data; it is small enough and the header is guaranteed to be
+ * at least CACHE_LINE_SIZE (i.e. 64) bytes, so we do have
+ * plenty of space at the start of the header. So the layout
+ * looks like this:
+ * [bucket_header] ... unused ... [rte_mempool_objhdr] [data...]
+ */
This is not always true.
If a use creates a mempool with the NO_CACHE_ALIGN, the header will be
small, without padding.
Thanks. I think it can be handled when bucket mempool implements own
callback to populate objects.
