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Message-ID: <77d6d8ee94d7149e6c33b10b78b43daf48ab8c70.1721546569.git.christophe.jaillet@wanadoo.fr>
Date: Sun, 21 Jul 2024 09:23:46 +0200
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Davidlohr Bueso <dave@...olabs.net>,
"Paul E. McKenney" <paulmck@...nel.org>,
Josh Triplett <josh@...htriplett.org>,
Frederic Weisbecker <frederic@...nel.org>,
Neeraj Upadhyay <neeraj.upadhyay@...nel.org>,
Joel Fernandes <joel@...lfernandes.org>,
Boqun Feng <boqun.feng@...il.com>,
Uladzislau Rezki <urezki@...il.com>,
Steven Rostedt <rostedt@...dmis.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Lai Jiangshan <jiangshanlai@...il.com>,
Zqiang <qiang.zhang1211@...il.com>
Cc: linux-kernel@...r.kernel.org,
kernel-janitors@...r.kernel.org,
Christophe JAILLET <christophe.jaillet@...adoo.fr>,
rcu@...r.kernel.org
Subject: [PATCH v2] refscale: Optimize process_durations()
process_durations() is not a hot path, but there is no good reason to
iterate over and over the data already in 'buf'.
Using a seq_buf saves some useless strcat() and the need of a temp buffer.
Data is written directly at the correct place.
Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
---
This patch is compile tested only.
I introduced a bug in v1 (see 1st item in the changes below), so it should
definitively be tested by someone!
v1 was un-usable because seq_buf_putc() was not exported. It is now
available since v6.7.
Because of the changes, I don't know if the previous R-b should kept.
In case, it was:
Reviewed-by: Steven Rostedt (Google) <rostedt@...dmis.org>
Reviewed-by: Davidlohr Bueso <dave@...olabs.net>
Changes in v2:
- Use seq_buf_printf() alseo for the first string, otherwise it would
get lost
- Use seq_buf_str() instead of seq_buf_terminate() because the API has
changed
v1: https://lore.kernel.org/all/bbbab32e3e104bdc2238724a6a4a85e539f49ddd.1698512661.git.christophe.jaillet@wanadoo.fr/
---
kernel/rcu/refscale.c | 25 ++++++++++++++-----------
1 file changed, 14 insertions(+), 11 deletions(-)
diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
index f4ea5b1ec068..cfec0648e141 100644
--- a/kernel/rcu/refscale.c
+++ b/kernel/rcu/refscale.c
@@ -28,6 +28,7 @@
#include <linux/rcupdate_trace.h>
#include <linux/reboot.h>
#include <linux/sched.h>
+#include <linux/seq_buf.h>
#include <linux/spinlock.h>
#include <linux/smp.h>
#include <linux/stat.h>
@@ -891,32 +892,34 @@ static u64 process_durations(int n)
{
int i;
struct reader_task *rt;
- char buf1[64];
+ struct seq_buf s;
char *buf;
u64 sum = 0;
buf = kmalloc(800 + 64, GFP_KERNEL);
if (!buf)
return 0;
- buf[0] = 0;
- sprintf(buf, "Experiment #%d (Format: <THREAD-NUM>:<Total loop time in ns>)",
- exp_idx);
+ seq_buf_init(&s, buf, 800 + 64);
+
+ seq_buf_printf(&s, "Experiment #%d (Format: <THREAD-NUM>:<Total loop time in ns>)",
+ exp_idx);
for (i = 0; i < n && !torture_must_stop(); i++) {
rt = &(reader_tasks[i]);
- sprintf(buf1, "%d: %llu\t", i, rt->last_duration_ns);
if (i % 5 == 0)
- strcat(buf, "\n");
- if (strlen(buf) >= 800) {
- pr_alert("%s", buf);
- buf[0] = 0;
+ seq_buf_putc(&s, '\n');
+
+ if (seq_buf_used(&s) >= 800) {
+ pr_alert("%s", seq_buf_str(&s));
+ seq_buf_clear(&s);
}
- strcat(buf, buf1);
+
+ seq_buf_printf(&s, "%d: %llu\t", i, rt->last_duration_ns);
sum += rt->last_duration_ns;
}
- pr_alert("%s\n", buf);
+ pr_alert("%s\n", seq_buf_str(&s));
kfree(buf);
return sum;
--
2.45.2
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