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@wanadoo.fr>
Tested-by: "Paul E. McKenney" <paulmck@kernel.org>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>

diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
index f4ea5b1ec068a7a72172bb0ec63c87be2d361b5f..cfec0648e1418750c2392a596a21ecfaf9cf32e3 100644 (file)
--- 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;