Messages in this thread Patch in this message | | | Date | Wed, 31 May 2023 13:58:53 +0200 | From | Peter Zijlstra <> | Subject | [RFC][PATCH 14/15] sched/fair: Add sched group latency support |
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From: Vincent Guittot <vincent.guittot@linaro.org>
Task can set its latency priority with sched_setattr(), which is then used to set the latency offset of its sched_enity, but sched group entities still have the default latency offset value.
Add a latency.nice field in cpu cgroup controller to set the latency priority of the group similarly to sched_setattr(). The latency priority is then used to set the offset of the sched_entities of the group.
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: K Prateek Nayak <kprateek.nayak@amd.com> Link: https://lkml.kernel.org/r/20230224093454.956298-7-vincent.guittot@linaro.org --- Documentation/admin-guide/cgroup-v2.rst | 10 ++++++++++ kernel/sched/core.c | 30 ++++++++++++++++++++++++++++++ kernel/sched/fair.c | 27 +++++++++++++++++++++++++++ kernel/sched/sched.h | 4 ++++ 4 files changed, 71 insertions(+)
--- a/Documentation/admin-guide/cgroup-v2.rst +++ b/Documentation/admin-guide/cgroup-v2.rst @@ -1121,6 +1121,16 @@ All time durations are in microseconds. values similar to the sched_setattr(2). This maximum utilization value is used to clamp the task specific maximum utilization clamp. + cpu.latency.nice + A read-write single value file which exists on non-root + cgroups. The default is "0". + + The nice value is in the range [-20, 19]. + + This interface file allows reading and setting latency using the + same values used by sched_setattr(2). The latency_nice of a group is + used to limit the impact of the latency_nice of a task outside the + group. Memory --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -11177,6 +11177,25 @@ static int cpu_idle_write_s64(struct cgr { return sched_group_set_idle(css_tg(css), idle); } + +static s64 cpu_latency_nice_read_s64(struct cgroup_subsys_state *css, + struct cftype *cft) +{ + return PRIO_TO_NICE(css_tg(css)->latency_prio); +} + +static int cpu_latency_nice_write_s64(struct cgroup_subsys_state *css, + struct cftype *cft, s64 nice) +{ + int prio; + + if (nice < MIN_NICE || nice > MAX_NICE) + return -ERANGE; + + prio = NICE_TO_PRIO(nice); + + return sched_group_set_latency(css_tg(css), prio); +} #endif static struct cftype cpu_legacy_files[] = { @@ -11191,6 +11210,11 @@ static struct cftype cpu_legacy_files[] .read_s64 = cpu_idle_read_s64, .write_s64 = cpu_idle_write_s64, }, + { + .name = "latency.nice", + .read_s64 = cpu_latency_nice_read_s64, + .write_s64 = cpu_latency_nice_write_s64, + }, #endif #ifdef CONFIG_CFS_BANDWIDTH { @@ -11408,6 +11432,12 @@ static struct cftype cpu_files[] = { .read_s64 = cpu_idle_read_s64, .write_s64 = cpu_idle_write_s64, }, + { + .name = "latency.nice", + .flags = CFTYPE_NOT_ON_ROOT, + .read_s64 = cpu_latency_nice_read_s64, + .write_s64 = cpu_latency_nice_write_s64, + }, #endif #ifdef CONFIG_CFS_BANDWIDTH { --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -12293,6 +12293,7 @@ int alloc_fair_sched_group(struct task_g goto err; tg->shares = NICE_0_LOAD; + tg->latency_prio = DEFAULT_PRIO; init_cfs_bandwidth(tg_cfs_bandwidth(tg)); @@ -12391,6 +12392,9 @@ void init_tg_cfs_entry(struct task_group } se->my_q = cfs_rq; + + set_latency_fair(se, tg->latency_prio - MAX_RT_PRIO); + /* guarantee group entities always have weight */ update_load_set(&se->load, NICE_0_LOAD); se->parent = parent; @@ -12519,6 +12523,29 @@ int sched_group_set_idle(struct task_gro mutex_unlock(&shares_mutex); return 0; +} + +int sched_group_set_latency(struct task_group *tg, int prio) +{ + int i; + + if (tg == &root_task_group) + return -EINVAL; + + mutex_lock(&shares_mutex); + + if (tg->latency_prio == prio) { + mutex_unlock(&shares_mutex); + return 0; + } + + tg->latency_prio = prio; + + for_each_possible_cpu(i) + set_latency_fair(tg->se[i], prio - MAX_RT_PRIO); + + mutex_unlock(&shares_mutex); + return 0; } #else /* CONFIG_FAIR_GROUP_SCHED */ --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -378,6 +378,8 @@ struct task_group { /* A positive value indicates that this is a SCHED_IDLE group. */ int idle; + /* latency priority of the group. */ + int latency_prio; #ifdef CONFIG_SMP /* @@ -488,6 +490,8 @@ extern int sched_group_set_shares(struct extern int sched_group_set_idle(struct task_group *tg, long idle); +extern int sched_group_set_latency(struct task_group *tg, int prio); + #ifdef CONFIG_SMP extern void set_task_rq_fair(struct sched_entity *se, struct cfs_rq *prev, struct cfs_rq *next);
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