On Sat, 28 Oct 2023 19:04:44 +0200 Christophe JAILLET <[email protected]> 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 <[email protected]> > --- > 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) <[email protected]> -- 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);
