[dpdk-dev] [PATCH] mempool: fix alignment of memzone length when populating

[Olivier Matz <olivier.matz@6wind.com>]

When populating a mempool with the default function, if there is not
enough virtually contiguous memory for the whole mempool, it will be
populated with several chunks. A chunk of the maximum available length
is requested with:

  mz = rte_memzone_reserve_aligned(..., len=0, ..., align=x)

If align is smaller than the page size, the length of the memzone may
not be a multiple of the page size. This makes
rte_mempool_populate_virt() to fail because it requires a page-aligned
length. This patch forces the memzone length to be a multiple of page
size.

The problem can be reproduced easily by allocating more than available
memory:
  ./build/app/testpmd -l 0,1 -- --total-num-mbufs=65536
  ...
  Cause: Creation of mbuf pool for socket 0 failed: Invalid argument

After the patch, the error code is correct:
  ./build/app/testpmd -l 0,1 -- --total-num-mbufs=65536
  ...
  Cause: Creation of mbuf pool for socket 0 failed: Cannot allocate memory

Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
Fixes: ba0009560c30 ("mempool: support new allocation methods")
---

Hi Anatoly,

Another	option to fix this issue could be to ensure that
rte_memzone_reserve_aligned(..., len=0, ..., align=x) returns a length
that is	multiple of page size. Something like:

        mz = rte_memzone_reserve_aligned(mz_name, 0,
  -                       mp->socket_id, flags, align);
  +                       mp->socket_id, flags, RTE_MAX(pg_sz, align));

Let me know if you prefer this way.

Thanks,
Olivier


 lib/librte_mempool/rte_mempool.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/librte_mempool/rte_mempool.c b/lib/librte_mempool/rte_mempool.c
index cf5d124ec..78c3e95ec 100644
--- a/lib/librte_mempool/rte_mempool.c
+++ b/lib/librte_mempool/rte_mempool.c
@@ -709,7 +709,7 @@ rte_mempool_populate_default(struct rte_mempool *mp)
 				(void *)(uintptr_t)mz);
 		else
 			ret = rte_mempool_populate_virt(mp, mz->addr,
-				mz->len, pg_sz,
+				RTE_ALIGN_FLOOR(mz->len, pg_sz), pg_sz,
 				rte_mempool_memchunk_mz_free,
 				(void *)(uintptr_t)mz);
 		if (ret < 0) {
-- 
2.11.0