linux-kernel - [tip:perf/urgent] perf bench numa: Fix immediate meeting of convergence condition

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Date:	Fri, 1 May 2015 03:16:01 -0700
From:	tip-bot for Petr Holasek <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	jolsa@...hat.com, tglx@...utronix.de, linux-kernel@...r.kernel.org,
	hpa@...or.com, acme@...hat.com, mingo@...nel.org,
	pholasek@...hat.com
Subject: [tip:perf/urgent] perf bench numa:
  Fix immediate meeting of convergence condition

Commit-ID:  1d90a685eb75a56648d7dd22c704a1a6da516de9
Gitweb:     http://git.kernel.org/tip/1d90a685eb75a56648d7dd22c704a1a6da516de9
Author:     Petr Holasek <pholasek@...hat.com>
AuthorDate: Thu, 16 Apr 2015 17:38:19 +0200
Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
CommitDate: Mon, 27 Apr 2015 13:57:50 -0300

perf bench numa: Fix immediate meeting of convergence condition

This patch fixes the race in the beginning of benchmark run when some
threads hasn't got assigned curr_cpu yet so they don't occur in
nodes-of-process stats and benchmark concludes that all remaining
threads are converged already.

The race can be reproduced with small amount of threads and some bigger
amount of shared process memory, e.g. one process, two threads and 5GB
of process memory.

Signed-off-by: Petr Holasek <pholasek@...hat.com>
Reviewed-by: Ingo Molnar <mingo@...nel.org>
Cc: Jiri Olsa <jolsa@...hat.com>
Link: http://lkml.kernel.org/r/1429198699-25039-4-git-send-email-pholasek@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/bench/numa.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tools/perf/bench/numa.c b/tools/perf/bench/numa.c
index cd872e9c..ba5efa4 100644
--- a/tools/perf/bench/numa.c
+++ b/tools/perf/bench/numa.c
@@ -828,6 +828,9 @@ static int count_process_nodes(int process_nr)
 		td = g->threads + task_nr;
 
 		node = numa_node_of_cpu(td->curr_cpu);
+		if (node < 0) /* curr_cpu was likely still -1 */
+			return 0;
+
 		node_present[node] = 1;
 	}
 
@@ -882,6 +885,11 @@ static void calc_convergence_compression(int *strong)
 	for (p = 0; p < g->p.nr_proc; p++) {
 		unsigned int nodes = count_process_nodes(p);
 
+		if (!nodes) {
+			*strong = 0;
+			return;
+		}
+
 		nodes_min = min(nodes, nodes_min);
 		nodes_max = max(nodes, nodes_max);
 	}
--
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