On Fri, Oct 22, 2021 at 06:51:11PM +0800, Li Zhijian wrote:
> 0Day/LKP observed that the refscale results become incompleted
> when a larger nruns(such as 300) is specified.
> It seems that printk() can accept < 1024 buffer at once.
> Print the buffer if its length exceeds 800 simply.
>
> CC: Philip Li <philip.li@xxxxxxxxx>
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Signed-off-by: Li Zhijian <lizhijian@xxxxxxxxxxxxxx>
Good catch! A couple of questions below.
Thanx, Paul
> ---
> kernel/rcu/refscale.c | 23 +++++++++++++----------
> 1 file changed, 13 insertions(+), 10 deletions(-)
>
> diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
> index 2cbe2a2ba387..b1b9052010fd 100644
> --- a/kernel/rcu/refscale.c
> +++ b/kernel/rcu/refscale.c
> @@ -604,7 +604,7 @@ static u64 process_durations(int n)
> char *buf;
> u64 sum = 0;
>
> - buf = kmalloc(128 + nreaders * 32, GFP_KERNEL);
> + buf = kmalloc(64 * 20, GFP_KERNEL);
This allocation (and the one below) is 1280 bytes rather than
1024 bytes. Why the extra couple hundred bytes?
> if (!buf)
> return 0;
> buf[0] = 0;
> @@ -617,13 +617,15 @@ static u64 process_durations(int n)
>
> if (i % 5 == 0)
> strcat(buf, "\n");
> + if (strlen(buf) > 800) {
> + pr_alert("%s", buf);
Does the tools/testing/selftests/rcutorture/bin/kvm-recheck-refscale.sh
script also require changes to handle the partial lines?
Same for the later comparison against 800.
> + buf[0] = 0;
> + }
> strcat(buf, buf1);
>
> sum += rt->last_duration_ns;
> }
> - strcat(buf, "\n");
> -
> - SCALEOUT("%s\n", buf);
> + pr_alert("%s\n", buf);
>
> kfree(buf);
> return sum;
> @@ -648,7 +650,7 @@ static int main_func(void *arg)
>
> VERBOSE_SCALEOUT("main_func task started");
> result_avg = kzalloc(nruns * sizeof(*result_avg), GFP_KERNEL);
> - buf = kzalloc(64 + nruns * 32, GFP_KERNEL);
> + buf = kzalloc(64 * 20, GFP_KERNEL);
> if (!result_avg || !buf) {
> VERBOSE_SCALEOUT_ERRSTRING("out of memory");
> errexit = true;
> @@ -701,10 +703,7 @@ static int main_func(void *arg)
> if (errexit)
> goto err;
>
> - buf[0] = 0;
> - strcat(buf, "\n");
> - strcat(buf, "Runs\tTime(ns)\n");
> -
> + pr_alert("Runs\tTime(ns)\n");
> for (exp = 0; exp < nruns; exp++) {
> u64 avg;
> u32 rem;
> @@ -712,9 +711,13 @@ static int main_func(void *arg)
> avg = div_u64_rem(result_avg[exp], 1000, &rem);
> sprintf(buf1, "%d\t%llu.%03u\n", exp + 1, avg, rem);
> strcat(buf, buf1);
> + if (strlen(buf) > 800) {
> + pr_alert("%s", buf);
> + buf[0] = 0;
> + }
> }
>
> - SCALEOUT("%s", buf);
> + pr_alert("%s", buf);
>
> err:
> // This will shutdown everything including us.
> --
> 2.33.0
>
>
>
