linux-kernel - [PATCH 3/3] perf bench numa: fix immediate meeting of convergence condition

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Message-Id: <1429198699-25039-4-git-send-email-pholasek@redhat.com>
Date:	Thu, 16 Apr 2015 17:38:19 +0200
From:	Petr Holasek <pholasek@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Jiri Olsa <jolsa@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	Petr Holasek <pholasek@...hat.com>
Subject: [PATCH 3/3] 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>
---
 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 72edc49..1704929 100644
--- a/tools/perf/bench/numa.c
+++ b/tools/perf/bench/numa.c
@@ -832,6 +832,9 @@ 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;
 	}
 
@@ -886,6 +889,11 @@ 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);
 	}
-- 
2.1.0

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