On 1/9/20 4:27 PM, Olivier Matz wrote:
> 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: sta...@dpdk.org
>
> Signed-off-by: Olivier Matz <olivier.m...@6wind.com>
LGTM except already mentioned bug with missing mz == NULL to retry loop.
Plus one minor question below.
> ---
> lib/librte_mempool/rte_mempool.c | 29 ++++++++++++-----------------
> 1 file changed, 12 insertions(+), 17 deletions(-)
>
> diff --git a/lib/librte_mempool/rte_mempool.c
> b/lib/librte_mempool/rte_mempool.c
> index bda361ce6..03c8d984c 100644
> --- a/lib/librte_mempool/rte_mempool.c
> +++ b/lib/librte_mempool/rte_mempool.c
> @@ -481,6 +481,7 @@ 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)
> @@ -560,30 +561,24 @@ 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;
Does it make sense to make max_alloc_size multiple of
min_chunk_size here? I think it could help to waste less
memory space.
> + } while (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
>
