On 10/05/20 13:56, Pavankumar Kondeti wrote:
> The intention of commit 96e74ebf8d59 ("sched/debug: Add task uclamp
> values to SCHED_DEBUG procfs") was to print requested and effective
> task uclamp values. The requested values printed are read from p->uclamp,
> which holds the last effective values. Fix this by printing the values
> from p->uclamp_req.
>
> Fixes: 96e74ebf8d59 ("sched/debug: Add task uclamp values to SCHED_DEBUG
> procfs")
> Signed-off-by: Pavankumar Kondeti <pkond...@codeaurora.org>
Argh, Qais pointed this out to me ~ a week ago, and I left this in my todo
stack. I goofed up, sorry!
As Pavan points out, p->uclamp[foo] is just a cache of uclamp_eff_value(p,
foo) from the last time p was enqueued and runnable - what we are
interested in is indeed comparing this with the *requested* value.
I wanted to send an example along with a patch, I guess that's the kick I
needed!
My setup is a busy loop, its per-task clamps are set to (256, 768) via
sched_setattr(), and it's shoved in a cpu cgroup with uclamp settings of
(50%, 50%)
On the current master (e99332e7b4cd ("gcc-10: mark more functions __init to
avoid section mismatch warnings")), this gives me:
$ uclamp-get $PID # via sched_getattr()
uclamp.min=256 uclamp.max=768
$ cat /proc/$PID/sched | grep uclamp
uclamp.min : 256
uclamp.max : 512
effective uclamp.min : 256
effective uclamp.max : 512
With Pavan's patch, I get:
$ uclamp-get $PID # via sched_getattr()
uclamp.min=256 uclamp.max=768
$ cat /proc/$PID/sched | grep uclamp
uclamp.min : 256
uclamp.max : 768
effective uclamp.min : 256
effective uclamp.max : 512
Minor print nit below, otherwise:
Tested-and-reviewed-by: Valentin Schneider <valentin.schnei...@arm.com>
Peter/Ingo, any chance this can go to sched/urgent? I know it's a debug
interface, but I'd rather have it land in a shape that makes sense. Again,
apologies for the goof.
> ---
> kernel/sched/debug.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
> index a562df5..239970b 100644
> --- a/kernel/sched/debug.c
> +++ b/kernel/sched/debug.c
> @@ -948,8 +948,8 @@ void proc_sched_show_task(struct task_struct *p, struct
> pid_namespace *ns,
> P(se.avg.util_est.enqueued);
> #endif
> #ifdef CONFIG_UCLAMP_TASK
> - __PS("uclamp.min", p->uclamp[UCLAMP_MIN].value);
> - __PS("uclamp.max", p->uclamp[UCLAMP_MAX].value);
> + __PS("uclamp.min", p->uclamp_req[UCLAMP_MIN].value);
> + __PS("uclamp.max", p->uclamp_req[UCLAMP_MAX].value);
While we're at it, I'd prepend this with "requested".
> __PS("effective uclamp.min", uclamp_eff_value(p, UCLAMP_MIN));
> __PS("effective uclamp.max", uclamp_eff_value(p, UCLAMP_MAX));
> #endif
