[RFC][PATCH 12/16] sched: A quick and dirty cgroup tagging interface

[Peter Zijlstra]

Marks all tasks in a cgroup as matching for core-scheduling.

Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
---
 kernel/sched/core.c  |   62 +++++++++++++++++++++++++++++++++++++++++++++++++++
 kernel/sched/sched.h |    4 +++
 2 files changed, 66 insertions(+)

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6608,6 +6608,15 @@ static void sched_change_group(struct ta
        tg = container_of(task_css_check(tsk, cpu_cgrp_id, true),
                          struct task_group, css);
        tg = autogroup_task_group(tsk, tg);
+
+#ifdef CONFIG_SCHED_CORE
+       if ((unsigned long)tsk->sched_task_group == tsk->core_cookie)
+               tsk->core_cookie = 0UL;
+
+       if (tg->tagged /* && !tsk->core_cookie ? */)
+               tsk->core_cookie = (unsigned long)tg;
+#endif
+
        tsk->sched_task_group = tg;
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
@@ -7067,6 +7076,43 @@ static u64 cpu_rt_period_read_uint(struc
 }
 #endif /* CONFIG_RT_GROUP_SCHED */
 
+#ifdef CONFIG_SCHED_CORE
+static u64 cpu_core_tag_read_u64(struct cgroup_subsys_state *css, struct 
cftype *cft)
+{
+       struct task_group *tg = css_tg(css);
+
+       return !!tg->tagged;
+}
+
+static int cpu_core_tag_write_u64(struct cgroup_subsys_state *css, struct 
cftype *cft, u64 val)
+{
+       struct task_group *tg = css_tg(css);
+       struct css_task_iter it;
+       struct task_struct *p;
+
+       if (val > 1)
+               return -ERANGE;
+
+       if (tg->tagged == !!val)
+               return 0;
+
+       tg->tagged = !!val;
+
+       if (!!val)
+               sched_core_get();
+
+       css_task_iter_start(css, 0, &it);
+       while ((p = css_task_iter_next(&it)))
+               p->core_cookie = !!val ? (unsigned long)tg : 0UL;
+       css_task_iter_end(&it);
+
+       if (!val)
+               sched_core_put();
+
+       return 0;
+}
+#endif
+
 static struct cftype cpu_legacy_files[] = {
 #ifdef CONFIG_FAIR_GROUP_SCHED
        {
@@ -7103,6 +7149,14 @@ static struct cftype cpu_legacy_files[]
                .write_u64 = cpu_rt_period_write_uint,
        },
 #endif
+#ifdef CONFIG_SCHED_CORE
+       {
+               .name = "tag",
+               .flags = CFTYPE_NOT_ON_ROOT,
+               .read_u64 = cpu_core_tag_read_u64,
+               .write_u64 = cpu_core_tag_write_u64,
+       },
+#endif
        { }     /* Terminate */
 };
 
@@ -7270,6 +7324,14 @@ static struct cftype cpu_files[] = {
                .write = cpu_max_write,
        },
 #endif
+#ifdef CONFIG_SCHED_CORE
+       {
+               .name = "tag",
+               .flags = CFTYPE_NOT_ON_ROOT,
+               .read_u64 = cpu_core_tag_read_u64,
+               .write_u64 = cpu_core_tag_write_u64,
+       },
+#endif
        { }     /* terminate */
 };
 
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -363,6 +363,10 @@ struct cfs_bandwidth {
 struct task_group {
        struct cgroup_subsys_state css;
 
+#ifdef CONFIG_SCHED_CORE
+       int                     tagged;
+#endif
+
 #ifdef CONFIG_FAIR_GROUP_SCHED
        /* schedulable entities of this group on each CPU */
        struct sched_entity     **se;