linux-kernel - [PATCH 5.7 74/79] selftests/net: relax cpu affinity requirement in msg

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Date:   Mon, 10 Aug 2020 17:21:33 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Colin Ian King <colin.king@...onical.com>,
        Willem de Bruijn <willemb@...gle.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 5.7 74/79] selftests/net: relax cpu affinity requirement in msg_zerocopy test

From: Willem de Bruijn <willemb@...gle.com>

[ Upstream commit 16f6458f2478b55e2b628797bc81a4455045c74e ]

The msg_zerocopy test pins the sender and receiver threads to separate
cores to reduce variance between runs.

But it hardcodes the cores and skips core 0, so it fails on machines
with the selected cores offline, or simply fewer cores.

The test mainly gives code coverage in automated runs. The throughput
of zerocopy ('-z') and non-zerocopy runs is logged for manual
inspection.

Continue even when sched_setaffinity fails. Just log to warn anyone
interpreting the data.

Fixes: 07b65c5b31ce ("test: add msg_zerocopy test")
Reported-by: Colin Ian King <colin.king@...onical.com>
Signed-off-by: Willem de Bruijn <willemb@...gle.com>
Acked-by: Colin Ian King <colin.king@...onical.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 tools/testing/selftests/net/msg_zerocopy.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

--- a/tools/testing/selftests/net/msg_zerocopy.c
+++ b/tools/testing/selftests/net/msg_zerocopy.c
@@ -125,9 +125,8 @@ static int do_setcpu(int cpu)
 	CPU_ZERO(&mask);
 	CPU_SET(cpu, &mask);
 	if (sched_setaffinity(0, sizeof(mask), &mask))
-		error(1, 0, "setaffinity %d", cpu);
-
-	if (cfg_verbose)
+		fprintf(stderr, "cpu: unable to pin, may increase variance.\n");
+	else if (cfg_verbose)
 		fprintf(stderr, "cpu: %u\n", cpu);
 
 	return 0;