patch 'app/testpmd: fix external buffer allocation' has been queued to stable release 21.11.1

[Kevin Traynor]

Hi,

FYI, your patch has been queued to stable release 21.11.1

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 02/26/22. 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.

Queued patches are on a temporary branch at:
https://github.com/kevintraynor/dpdk-stable

This queued commit can be viewed at:
https://github.com/kevintraynor/dpdk-stable/commit/ef94549efe574bddcc8d65a9ac66b4b4734d7ffe

Thanks.

Kevin

---
>From ef94549efe574bddcc8d65a9ac66b4b4734d7ffe Mon Sep 17 00:00:00 2001
From: Dmitry Kozlyuk <dkozlyuk at nvidia.com>
Date: Fri, 17 Dec 2021 11:58:16 +0200
Subject: [PATCH] app/testpmd: fix external buffer allocation

[ upstream commit 13b196425ce371a82fa8008fa46ce66861d4202b ]

External pinned buffer memory (--mp-alloc=xbuf)
was allocated as multiple IOVA-contiguous memzones
of 2M size and 2M alignment.
Due to the malloc overhead and the alignment requirement,
each 2M memzone consumed 4M of hugepage memory:
2M of usable memory + X of malloc overhead + (2M-X) padding.
The allocation often failed with 2M hugepages and IOVA-as-PA
if a PA-contiguous span of 2 hugepages could not be found.
Also, with any hugepage size and IOVA mode
memory consumption was almost 2x of the usable amount.

Alignment requirement of 2M for external buffers is redundant.
It was an attempt to ensure IOVA-contiguity
by forcing memzones to start at hugepage boundaries,
while 2M size intended to leave no unused space on the page.
As shown above, this in fact caused excessive memory consumption
and decreased the chance of a successful allocation.
RTE_MEMZONE_F_IOVA_CONTIG already ensures IOVA-contiguity.

Remove the alignment requirement.
Reduce the memzone size by the malloc overhead size (4 cache lines),
so that memory consumption for each memzone is
(2M-X) of usable memory + X of malloc overhead = 2M.
This also means that whenever there are free 2M hugepages,
an IOVA-contiguous memzone can always be allocated.

Fixes: 72512e1897b2 ("app/testpmd: add mempool with external data buffers")

Signed-off-by: Dmitry Kozlyuk <dkozlyuk at nvidia.com>
Signed-off-by: Viacheslav Ovsiienko <viacheslavo at nvidia.com>
---
 app/test-pmd/testpmd.c | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/app/test-pmd/testpmd.c b/app/test-pmd/testpmd.c
index 6c387bde84..e1da961311 100644
--- a/app/test-pmd/testpmd.c
+++ b/app/test-pmd/testpmd.c
@@ -85,5 +85,11 @@
 
 #define EXTMEM_HEAP_NAME "extmem"
-#define EXTBUF_ZONE_SIZE RTE_PGSIZE_2M
+/*
+ * Zone size with the malloc overhead (max of debug and release variants)
+ * must fit into the smallest supported hugepage size (2M),
+ * so that an IOVA-contiguous zone of this size can always be allocated
+ * if there are free 2M hugepages.
+ */
+#define EXTBUF_ZONE_SIZE (RTE_PGSIZE_2M - 4 * RTE_CACHE_LINE_SIZE)
 
 uint16_t verbose_level = 0; /**< Silent by default. */
@@ -1062,10 +1068,9 @@ setup_extbuf(uint32_t nb_mbufs, uint16_t mbuf_sz, unsigned int socket_id,
 			break;
 		}
-		mz = rte_memzone_reserve_aligned(mz_name, EXTBUF_ZONE_SIZE,
-						 socket_id,
-						 RTE_MEMZONE_IOVA_CONTIG |
-						 RTE_MEMZONE_1GB |
-						 RTE_MEMZONE_SIZE_HINT_ONLY,
-						 EXTBUF_ZONE_SIZE);
+		mz = rte_memzone_reserve(mz_name, EXTBUF_ZONE_SIZE,
+					 socket_id,
+					 RTE_MEMZONE_IOVA_CONTIG |
+					 RTE_MEMZONE_1GB |
+					 RTE_MEMZONE_SIZE_HINT_ONLY);
 		if (mz == NULL) {
 			/*
-- 
2.34.1

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2022-02-21 15:22:46.232098310 +0000
+++ 0073-app-testpmd-fix-external-buffer-allocation.patch	2022-02-21 15:22:44.159704279 +0000
@@ -1 +1 @@
-From 13b196425ce371a82fa8008fa46ce66861d4202b Mon Sep 17 00:00:00 2001
+From ef94549efe574bddcc8d65a9ac66b4b4734d7ffe Mon Sep 17 00:00:00 2001
@@ -5,0 +6,2 @@
+[ upstream commit 13b196425ce371a82fa8008fa46ce66861d4202b ]
+
@@ -33 +34,0 @@
-Cc: stable at dpdk.org