On Sat, 28 Oct 2023 19:04:44 +0200
Christophe JAILLET <christophe.jaillet@xxxxxxxxxx> wrote:
> 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.
>
Agreed.
> Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
> ---
> kernel/rcu/refscale.c | 20 +++++++++++++-------
> 1 file changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
> index 2c2648a3ad30..861485d865ec 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>
> @@ -890,31 +891,36 @@ 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;
> +
> + seq_buf_init(&s, buf, 800 + 64);
> +
> sprintf(buf, "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) {
> + seq_buf_putc(&s, '\n');
I was confused here thinking it was originally adding a '\n' to buf1 on
i % 5, but it's adding it to buf!
Yeah, using seq_buf is much less confusing and then less error prone.
Reviewed-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
-- Steve
> +
> + if (seq_buf_used(&s) >= 800) {
> + seq_buf_terminate(&s);
> pr_alert("%s", buf);
> - buf[0] = 0;
> + seq_buf_clear(&s);
> }
> - strcat(buf, buf1);
> +
> + seq_buf_printf(&s, "%d: %llu\t", i, rt->last_duration_ns);
>
> sum += rt->last_duration_ns;
> }
> + seq_buf_terminate(&s);
> pr_alert("%s\n", buf);
>
> kfree(buf);
