[dpdk-stable] patch 'app/eventdev: fix SMP barrier in performance test' has been queued to stable release 19.11.7

[Christian Ehrhardt]

Hi,

FYI, your patch has been queued to stable release 19.11.7

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 02/06/21. 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/cpaelzer/dpdk-stable-queue

This queued commit can be viewed at:
https://github.com/cpaelzer/dpdk-stable-queue/commit/bd99c999510c1cca6f52a3efaca6842be63c77f6

Thanks.

Christian Ehrhardt <christian.ehrhardt at canonical.com>

---
>From bd99c999510c1cca6f52a3efaca6842be63c77f6 Mon Sep 17 00:00:00 2001
From: Feifei Wang <feifei.wang2 at arm.com>
Date: Thu, 14 Jan 2021 15:08:26 +0800
Subject: [PATCH] app/eventdev: fix SMP barrier in performance test

[ upstream commit c7c033d173f2d4f14834c0fb942b84725ac940e8 ]

This patch fixes RTE SMP barrier bugs for the perf test of eventdev.

For the "perf_process_last_stage" function, wmb after storing
processed_pkts should be moved before it. This is because the worker
lcore should ensure it has really finished data processing, e.g. event
stored into buffers, before the shared variables "w->processed_pkts"are
stored.

For the "perf_process_last_stage_latency", on the one hand, the wmb
should be moved before storing into "w->processed_pkts". The reason is
the same as above. But on the other hand, for "w->latency", wmb is
unnecessary due to data dependency.

Fixes: 2369f73329f8 ("app/testeventdev: add perf queue worker functions")

Signed-off-by: Feifei Wang <feifei.wang2 at arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang at arm.com>
Acked-by: Pavan Nikhilesh <pbhagavatula at marvell.com>
---
 app/test-eventdev/test_perf_common.h | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/app/test-eventdev/test_perf_common.h b/app/test-eventdev/test_perf_common.h
index d8fbee6d89..e095da9a47 100644
--- a/app/test-eventdev/test_perf_common.h
+++ b/app/test-eventdev/test_perf_common.h
@@ -97,8 +97,13 @@ perf_process_last_stage(struct rte_mempool *const pool,
 		void *bufs[], int const buf_sz, uint8_t count)
 {
 	bufs[count++] = ev->event_ptr;
-	w->processed_pkts++;
+
+	/* wmb here ensures event_prt is stored before
+	 * updating the number of processed packets
+	 * for worker lcores
+	 */
 	rte_smp_wmb();
+	w->processed_pkts++;
 
 	if (unlikely(count == buf_sz)) {
 		count = 0;
@@ -116,6 +121,12 @@ perf_process_last_stage_latency(struct rte_mempool *const pool,
 	struct perf_elt *const m = ev->event_ptr;
 
 	bufs[count++] = ev->event_ptr;
+
+	/* wmb here ensures event_prt is stored before
+	 * updating the number of processed packets
+	 * for worker lcores
+	 */
+	rte_smp_wmb();
 	w->processed_pkts++;
 
 	if (unlikely(count == buf_sz)) {
@@ -127,7 +138,6 @@ perf_process_last_stage_latency(struct rte_mempool *const pool,
 	}
 
 	w->latency += latency;
-	rte_smp_wmb();
 	return count;
 }
 
-- 
2.30.0

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2021-02-04 12:04:31.840364133 +0100
+++ 0092-app-eventdev-fix-SMP-barrier-in-performance-test.patch	2021-02-04 12:04:28.098789794 +0100
@@ -1 +1 @@
-From c7c033d173f2d4f14834c0fb942b84725ac940e8 Mon Sep 17 00:00:00 2001
+From bd99c999510c1cca6f52a3efaca6842be63c77f6 Mon Sep 17 00:00:00 2001
@@ -5,0 +6,2 @@
+[ upstream commit c7c033d173f2d4f14834c0fb942b84725ac940e8 ]
+
@@ -20 +21,0 @@
-Cc: stable at dpdk.org
@@ -30 +31 @@
-index ff9705df88..e7233e5a5b 100644
+index d8fbee6d89..e095da9a47 100644