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SubjectRe: [RFC 3/3] Allow sched_{get,set}attr to change latency_tolerance of the task
On 11/25/19 15:16, Parth Shah wrote:
> Introduce the latency_tolerance attribute to sched_attr and provide a
> mechanism to change the value with the use of sched_setattr/sched_getattr
> syscall.
>
> Also add new flag "SCHED_FLAG_LATENCY_TOLERANCE" to hint the change in
> latency_tolerance of the task on every sched_setattr syscall.
>
> Signed-off-by: Parth Shah <parth@linux.ibm.com>
> ---
> include/uapi/linux/sched.h | 4 +++-
> include/uapi/linux/sched/types.h | 2 ++
> kernel/sched/core.c | 15 +++++++++++++++
> kernel/sched/sched.h | 1 +
> 4 files changed, 21 insertions(+), 1 deletion(-)
>
> diff --git a/include/uapi/linux/sched.h b/include/uapi/linux/sched.h
> index b3105ac1381a..73db430d11b6 100644
> --- a/include/uapi/linux/sched.h
> +++ b/include/uapi/linux/sched.h
> @@ -71,6 +71,7 @@ struct clone_args {
> #define SCHED_FLAG_KEEP_PARAMS 0x10
> #define SCHED_FLAG_UTIL_CLAMP_MIN 0x20
> #define SCHED_FLAG_UTIL_CLAMP_MAX 0x40
> +#define SCHED_FLAG_LATENCY_TOLERANCE 0x80
>
> #define SCHED_FLAG_KEEP_ALL (SCHED_FLAG_KEEP_POLICY | \
> SCHED_FLAG_KEEP_PARAMS)
> @@ -82,6 +83,7 @@ struct clone_args {
> SCHED_FLAG_RECLAIM | \
> SCHED_FLAG_DL_OVERRUN | \
> SCHED_FLAG_KEEP_ALL | \
> - SCHED_FLAG_UTIL_CLAMP)
> + SCHED_FLAG_UTIL_CLAMP | \
> + SCHED_FLAG_LATENCY_TOLERANCE)
>
> #endif /* _UAPI_LINUX_SCHED_H */
> diff --git a/include/uapi/linux/sched/types.h b/include/uapi/linux/sched/types.h
> index c852153ddb0d..960774ac0c70 100644
> --- a/include/uapi/linux/sched/types.h
> +++ b/include/uapi/linux/sched/types.h
> @@ -118,6 +118,8 @@ struct sched_attr {
> __u32 sched_util_min;
> __u32 sched_util_max;
>
> + /* latency requirement hints */
> + __s32 sched_latency_tolerance;
> };
>
> #endif /* _UAPI_LINUX_SCHED_TYPES_H */
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index ea7abbf5c1bb..dfd36ec14404 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -4695,6 +4695,9 @@ static void __setscheduler_params(struct task_struct *p,
> p->rt_priority = attr->sched_priority;
> p->normal_prio = normal_prio(p);
> set_load_weight(p, true);
> +
> + /* Change latency tolerance of the task if !SCHED_FLAG_KEEP_PARAMS */
> + p->latency_tolerance = attr->sched_latency_tolerance;
> }
>
> /* Actually do priority change: must hold pi & rq lock. */
> @@ -4852,6 +4855,13 @@ static int __sched_setscheduler(struct task_struct *p,
> return retval;
> }
>
> + if (attr->sched_flags & SCHED_FLAG_LATENCY_TOLERANCE) {
> + if (attr->sched_latency_tolerance > MAX_LATENCY_TOLERANCE)
> + return -EINVAL;
> + if (attr->sched_latency_tolerance < MIN_LATENCY_TOLERANCE)
> + return -EINVAL;
> + }
> +
> if (pi)
> cpuset_read_lock();
>
> @@ -4886,6 +4896,9 @@ static int __sched_setscheduler(struct task_struct *p,
> goto change;
> if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)
> goto change;
> + if (attr->sched_flags & SCHED_FLAG_LATENCY_TOLERANCE &&
> + attr->sched_latency_tolerance != p->latency_tolerance)
> + goto change;
>
> p->sched_reset_on_fork = reset_on_fork;
> retval = 0;
> @@ -5392,6 +5405,8 @@ SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
> else
> kattr.sched_nice = task_nice(p);
>
> + kattr.sched_latency_tolerance = p->latency_tolerance;
> +
> #ifdef CONFIG_UCLAMP_TASK
> kattr.sched_util_min = p->uclamp_req[UCLAMP_MIN].value;
> kattr.sched_util_max = p->uclamp_req[UCLAMP_MAX].value;
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index 0db2c1b3361e..bb181175954b 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -21,6 +21,7 @@
> #include <linux/sched/nohz.h>
> #include <linux/sched/numa_balancing.h>
> #include <linux/sched/prio.h>
> +#include <linux/sched/latency_tolerance.h>

nit: keep in alphabatical order.

The series looks good to me except for the 2 minor nits. Thanks for taking care
of this!

Reviewed-by: Qais Yousef <qais.yousef@arm.com>

Cheers

--
Qais Yousef

> #include <linux/sched/rt.h>
> #include <linux/sched/signal.h>
> #include <linux/sched/smt.h>
> --
> 2.17.2
>

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