[dpdk-stable] patch 'mempool: fix slow allocation of large pools' has been queued to stable release 19.11.1

[luca.boccassi at gmail.com]

Hi,

FYI, your patch has been queued to stable release 19.11.1

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 02/13/20. So please
shout if anyone has objections.

Also note that after the patch there's a diff of the upstream commit vs the
patch applied to the branch. This will indicate if there was any rebasing
needed to apply to the stable branch. If there were code changes for rebasing
(ie: not only metadata diffs), please double check that the rebase was
correctly done.

Thanks.

Luca Boccassi

---
>From b019099e527f0ca0f120b32cb24845594c029cdd Mon Sep 17 00:00:00 2001
From: Olivier Matz <olivier.matz at 6wind.com>
Date: Fri, 17 Jan 2020 10:51:49 +0100
Subject: [PATCH] mempool: fix slow allocation of large pools

[ upstream commit 3a3d0c75b43e8d1670c5ea6bf85cb3e1e60dfa2b ]

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")

Signed-off-by: Olivier Matz <olivier.matz at 6wind.com>
Acked-by: Anatoly Burakov <anatoly.burakov at intel.com>
Reviewed-by: Andrew Rybchenko <arybchenko at solarflare.com>
Tested-by: Ali Alnubani <alialnu at mellanox.com>
---
 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 f8d453d21f..aea597224a 100644
--- a/lib/librte_mempool/rte_mempool.c
+++ b/lib/librte_mempool/rte_mempool.c
@@ -463,6 +463,7 @@ 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)
@@ -542,30 +543,24 @@ 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
-- 
2.20.1

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2020-02-11 11:17:42.718460591 +0000
+++ 0113-mempool-fix-slow-allocation-of-large-pools.patch	2020-02-11 11:17:38.580004713 +0000
@@ -1,8 +1,10 @@
-From 3a3d0c75b43e8d1670c5ea6bf85cb3e1e60dfa2b Mon Sep 17 00:00:00 2001
+From b019099e527f0ca0f120b32cb24845594c029cdd Mon Sep 17 00:00:00 2001
 From: Olivier Matz <olivier.matz at 6wind.com>
 Date: Fri, 17 Jan 2020 10:51:49 +0100
 Subject: [PATCH] mempool: fix slow allocation of large pools
 
+[ upstream commit 3a3d0c75b43e8d1670c5ea6bf85cb3e1e60dfa2b ]
+
 When allocating a mempool which is larger than the largest
 available area, it can take a lot of time:
 
@@ -29,7 +31,6 @@
 below min_chunk_size, stop and return an error.
 
 Fixes: eba11e364614 ("mempool: reduce wasted space on populate")
-Cc: stable at dpdk.org
 
 Signed-off-by: Olivier Matz <olivier.matz at 6wind.com>
 Acked-by: Anatoly Burakov <anatoly.burakov at intel.com>