mempool: fix slow allocation of large mempools

When allocating a mempool which is larger than the largest
available area, it can take a lot of time:

a- the mempool calculate the required memory size, and tries
   to allocate it, it fails
b- then it tries to allocate the largest available area (this
   does not request new huge pages)
c- add this zone to the mempool, this triggers the allocation
   of a mem hdr, which request a new huge page
d- back to a- until mempool is populated or until there is no
   more memory

This can take a lot of time to finally fail (several minutes): in step
a- it takes all available hugepages on the system, then release them
after it fails.

The problem appeared with commit eba11e364614 ("mempool: reduce wasted
space on populate"), because smaller chunks are now allowed. Previously,
it had to be at least one page size, which is not the case in step b-.

To fix this, implement our own way to allocate the largest available
area instead of using the feature from memzone: if an allocation fails,
try to divide the size by 2 and retry. When the requested size falls
below min_chunk_size, stop and return an error.

Fixes: eba11e364614 ("mempool: reduce wasted space on populate")
Cc: stable@dpdk.org
Signed-off-by: Olivier Matz <olivier.matz@6wind.com>

diff --git a/lib/librte_mempool/rte_mempool.c b/lib/librte_mempool/rte_mempool.c
index ff95f41..a8ad092 100644 (file)
--- a/lib/librte_mempool/rte_mempool.c
+++ b/lib/librte_mempool/rte_mempool.c
@@ -505,6 +505,7 @@ rte_mempool_populate_default(struct rte_mempool *mp)
        unsigned mz_id, n;
        int ret;
        bool need_iova_contig_obj;
+       size_t max_alloc_size = SIZE_MAX;
 
        ret = mempool_ops_alloc_once(mp);
        if (ret != 0)
@@ -584,30 +585,24 @@ rte_mempool_populate_default(struct rte_mempool *mp)
                if (min_chunk_size == (size_t)mem_size)
                        mz_flags |= RTE_MEMZONE_IOVA_CONTIG;
 
-               mz = rte_memzone_reserve_aligned(mz_name, mem_size,
+               /* Allocate a memzone, retrying with a smaller area on ENOMEM */
+               do {
+                       mz = rte_memzone_reserve_aligned(mz_name,
+                               RTE_MIN((size_t)mem_size, max_alloc_size),
                                mp->socket_id, mz_flags, align);
 
-               /* don't try reserving with 0 size if we were asked to reserve
-                * IOVA-contiguous memory.
-                */
-               if (min_chunk_size < (size_t)mem_size && mz == NULL) {
-                       /* not enough memory, retry with the biggest zone we
-                        * have
-                        */
-                       mz = rte_memzone_reserve_aligned(mz_name, 0,
-                                       mp->socket_id, mz_flags, align);
-               }
+                       if (mz == NULL && rte_errno != ENOMEM)
+                               break;
+
+                       max_alloc_size = RTE_MIN(max_alloc_size,
+                                               (size_t)mem_size) / 2;
+               } while (mz == NULL && max_alloc_size >= min_chunk_size);
+
                if (mz == NULL) {
                        ret = -rte_errno;
                        goto fail;
                }
 
-               if (mz->len < min_chunk_size) {
-                       rte_memzone_free(mz);
-                       ret = -ENOMEM;
-                       goto fail;
-               }
-
                if (need_iova_contig_obj)
                        iova = mz->iova;
                else