linux-kernel - [PATCH tip/core/rcu 10/30] refperf: Dynamically allocate experiment-summary output buffer

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Date:   Mon, 22 Jun 2020 17:29:53 -0700
From:   paulmck@...nel.org
To:     rcu@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, kernel-team@...com, mingo@...nel.org,
        jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
        rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
        fweisbec@...il.com, oleg@...hat.com, joel@...lfernandes.org,
        "Paul E. McKenney" <paulmck@...nel.org>
Subject: [PATCH tip/core/rcu 10/30] refperf: Dynamically allocate experiment-summary output buffer

From: "Paul E. McKenney" <paulmck@...nel.org>

Currently, the buffer used to accumulate the experiment-summary output
is fixed size, which will cause problems if someone decides to run
one hundred experiments.  This commit therefore dynamically allocates
this buffer.

Cc: Joel Fernandes (Google) <joel@...lfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 kernel/rcu/refperf.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/kernel/rcu/refperf.c b/kernel/rcu/refperf.c
index 6324449..75b9cce 100644
--- a/kernel/rcu/refperf.c
+++ b/kernel/rcu/refperf.c
@@ -333,9 +333,10 @@ u64 process_durations(int n)
 // point all the timestamps are printed.
 static int main_func(void *arg)
 {
+	bool errexit = false;
 	int exp, r;
 	char buf1[64];
-	char buf[512];
+	char *buf;
 	u64 *result_avg;
 
 	set_cpus_allowed_ptr(current, cpumask_of(nreaders % nr_cpu_ids));
@@ -343,8 +344,11 @@ static int main_func(void *arg)
 
 	VERBOSE_PERFOUT("main_func task started");
 	result_avg = kzalloc(nruns * sizeof(*result_avg), GFP_KERNEL);
-	if (!result_avg)
+	buf = kzalloc(64 + nruns * 32, GFP_KERNEL);
+	if (!result_avg || !buf) {
 		VERBOSE_PERFOUT_ERRSTRING("out of memory");
+		errexit = true;
+	}
 	atomic_inc(&n_init);
 
 	// Wait for all threads to start.
@@ -354,7 +358,7 @@ static int main_func(void *arg)
 
 	// Start exp readers up per experiment
 	for (exp = 0; exp < nruns && !torture_must_stop(); exp++) {
-		if (!result_avg)
+		if (errexit)
 			break;
 		if (torture_must_stop())
 			goto end;
@@ -391,13 +395,13 @@ static int main_func(void *arg)
 	strcat(buf, "Threads\tTime(ns)\n");
 
 	for (exp = 0; exp < nruns; exp++) {
-		if (!result_avg)
+		if (errexit)
 			break;
 		sprintf(buf1, "%d\t%llu.%03d\n", exp + 1, result_avg[exp] / 1000, (int)(result_avg[exp] % 1000));
 		strcat(buf, buf1);
 	}
 
-	if (result_avg)
+	if (!errexit)
 		PERFOUT("%s", buf);
 
 	// This will shutdown everything including us.
@@ -412,6 +416,8 @@ static int main_func(void *arg)
 
 end:
 	torture_kthread_stopping("main_func");
+	kfree(result_avg);
+	kfree(buf);
 	return 0;
 }
 
-- 
2.9.5