Messages in this thread | | | Subject | Re: [RFC 3/3] Allow sched_{get,set}attr to change latency_tolerance of the task | From | Parth Shah <> | Date | Tue, 3 Dec 2019 21:21:55 +0530 |
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On 12/3/19 2:09 PM, Qais Yousef wrote: > 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.
ok.
> > The series looks good to me except for the 2 minor nits. Thanks for taking care > of this!
My pleasure. Infact, I'm trying to write patches around what Subhra posted for reducing wakeup scans https://lkml.org/lkml/2019/8/30/829 and few ideas from Peter's patch https://lkml.org/lkml/2018/5/30/632. Aim here is to reduce scans for lower latency_tolerance tasks and will post out soon which uses this feature.
> > Reviewed-by: Qais Yousef <qais.yousef@arm.com>
Thanks. Will add it.
> > 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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