[patch] sched/fair: Move se->vruntime normalization state into struct sched_entity
From: Mike Galbraith
Date: Sun May 22 2016 - 03:00:30 EST
On Sat, 2016-05-21 at 21:00 +0200, Mike Galbraith wrote:
> On Sat, 2016-05-21 at 16:04 +0200, Mike Galbraith wrote:
>
> > Wakees that were not migrated/normalized eat an unwanted min_vruntime,
> > and likely take a size XXL latency hit. Big box running master bled
> > profusely under heavy load until I turned TTWU_QUEUE off.
May as well make it official and against master.today. Fly or die
little patchlet.
sched/fair: Move se->vruntime normalization state into struct sched_entity
b5179ac70de ceased globally normalizing wakee vruntime in ttwu(), leaving
sched_ttwu_pending() with the need to know whether each wakee on wake_list
was migrated or not, to pass that on to fair class functions so they can
DTRT wrt vruntime normalization. Store vruntime normalization state in
struct sched_entity, so fair class functions that need it always have it,
and sched_ttwu_pending() again doesn't need to care whether tasks on the
wake_list have been migrated or not.
Since there are now no consumers of ENQUEUE_MIGRATED, drop it as well.
master v4.6-8889-gf6c658df6385 virgin
256 49096 71698.99 MB/sec warmup 1 sec latency 1136.488 ms
256 155009 72862.08 MB/sec execute 1 sec latency 3136.900 ms
256 207430 72628.04 MB/sec execute 2 sec latency 4137.001 ms
256 259635 72442.97 MB/sec execute 3 sec latency 5137.105 ms
256 311905 72371.84 MB/sec execute 4 sec latency 6137.214 ms
256 364210 72564.99 MB/sec execute 5 sec latency 7137.323 ms
256 416551 72598.74 MB/sec execute 6 sec latency 5816.895 ms
256 468824 72601.54 MB/sec execute 7 sec latency 6815.386 ms
256 520996 72621.87 MB/sec execute 8 sec latency 7815.499 ms
256 573113 72608.75 MB/sec execute 9 sec latency 8815.609 ms
256 cleanup 10 sec
0 cleanup 10 sec
master v4.6-8889-gf6c658df6385 post
256 51527 75357.55 MB/sec warmup 1 sec latency 21.591 ms
256 157610 73188.06 MB/sec execute 1 sec latency 12.985 ms
256 210089 72809.01 MB/sec execute 2 sec latency 11.543 ms
256 262554 72681.86 MB/sec execute 3 sec latency 0.209 ms
256 315432 72798.65 MB/sec execute 4 sec latency 0.206 ms
256 368162 72963.33 MB/sec execute 5 sec latency 8.052 ms
256 420854 72976.50 MB/sec execute 6 sec latency 0.221 ms
256 473420 72953.76 MB/sec execute 7 sec latency 0.198 ms
256 525859 73011.17 MB/sec execute 8 sec latency 2.810 ms
256 578301 73052.84 MB/sec execute 9 sec latency 0.247 ms
256 cleanup 10 sec
0 cleanup 10 sec
Fixes: b5179ac70de sched/fair: Prepare to fix fairness problems on migration
Signed-off-by: Mike Galbraith <umgwanakikbuti@xxxxxxxxx>
---
include/linux/sched.h | 1
kernel/sched/core.c | 6 +----
kernel/sched/fair.c | 60 ++++++++++++++++++++------------------------------
3 files changed, 28 insertions(+), 39 deletions(-)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1319,6 +1319,7 @@ struct sched_entity {
struct rb_node run_node;
struct list_head group_node;
unsigned int on_rq;
+ bool normalized;
u64 exec_start;
u64 sum_exec_runtime;
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1719,9 +1719,6 @@ ttwu_do_activate(struct rq *rq, struct t
#ifdef CONFIG_SMP
if (p->sched_contributes_to_load)
rq->nr_uninterruptible--;
-
- if (wake_flags & WF_MIGRATED)
- en_flags |= ENQUEUE_MIGRATED;
#endif
ttwu_activate(rq, p, en_flags);
@@ -1774,7 +1771,7 @@ void sched_ttwu_pending(void)
* See ttwu_queue(); we only call ttwu_queue_remote() when
* its a x-cpu wakeup.
*/
- ttwu_do_activate(rq, p, WF_MIGRATED, cookie);
+ ttwu_do_activate(rq, p, 0, cookie);
}
lockdep_unpin_lock(&rq->lock, cookie);
@@ -2166,6 +2163,7 @@ static void __sched_fork(unsigned long c
p->se.prev_sum_exec_runtime = 0;
p->se.nr_migrations = 0;
p->se.vruntime = 0;
+ p->se.normalized = true;
INIT_LIST_HEAD(&p->se.group_node);
#ifdef CONFIG_FAIR_GROUP_SCHED
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3230,6 +3230,7 @@ place_entity(struct cfs_rq *cfs_rq, stru
/* ensure we never gain time by being placed backwards. */
se->vruntime = max_vruntime(se->vruntime, vruntime);
+ se->normalized = false;
}
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
@@ -3285,29 +3286,40 @@ static inline void check_schedstat_requi
* CPU and an up-to-date min_vruntime on the destination CPU.
*/
+static void normalize_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
+{
+ se->vruntime -= cfs_rq->min_vruntime;
+ se->normalized = true;
+}
+
+static void renormalize_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
+{
+ se->vruntime += cfs_rq->min_vruntime;
+ se->normalized = false;
+}
+
static void
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{
- bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED);
- bool curr = cfs_rq->curr == se;
+ bool renorm = se->normalized, curr = cfs_rq->curr == se;
/*
- * If we're the current task, we must renormalise before calling
+ * If we're the current task, we must renormalize before calling
* update_curr().
*/
if (renorm && curr)
- se->vruntime += cfs_rq->min_vruntime;
+ renormalize_entity(cfs_rq, se);
update_curr(cfs_rq);
/*
- * Otherwise, renormalise after, such that we're placed at the current
+ * Otherwise, renormalize after, such that we're placed at the current
* moment in time, instead of some random moment in the past. Being
* placed in the past could significantly boost this task to the
* fairness detriment of existing tasks.
*/
if (renorm && !curr)
- se->vruntime += cfs_rq->min_vruntime;
+ renormalize_entity(cfs_rq, se);
enqueue_entity_load_avg(cfs_rq, se);
account_entity_enqueue(cfs_rq, se);
@@ -3406,7 +3418,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, st
* movement in our normalized position.
*/
if (!(flags & DEQUEUE_SLEEP))
- se->vruntime -= cfs_rq->min_vruntime;
+ normalize_entity(cfs_rq, se);
/* return excess runtime on last dequeue */
return_cfs_rq_runtime(cfs_rq);
@@ -5408,7 +5420,7 @@ static void migrate_task_rq_fair(struct
min_vruntime = cfs_rq->min_vruntime;
#endif
- se->vruntime -= min_vruntime;
+ normalize_entity(cfs_rq, se);
}
/*
@@ -8319,7 +8331,7 @@ static void task_fork_fair(struct task_s
resched_curr(rq);
}
- se->vruntime -= cfs_rq->min_vruntime;
+ normalize_entity(cfs_rq, se);
raw_spin_unlock_irqrestore(&rq->lock, flags);
}
@@ -8348,29 +8360,7 @@ prio_changed_fair(struct rq *rq, struct
static inline bool vruntime_normalized(struct task_struct *p)
{
- struct sched_entity *se = &p->se;
-
- /*
- * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
- * the dequeue_entity(.flags=0) will already have normalized the
- * vruntime.
- */
- if (p->on_rq)
- return true;
-
- /*
- * When !on_rq, vruntime of the task has usually NOT been normalized.
- * But there are some cases where it has already been normalized:
- *
- * - A forked child which is waiting for being woken up by
- * wake_up_new_task().
- * - A task which has been woken up by try_to_wake_up() and
- * waiting for actually being woken up by sched_ttwu_pending().
- */
- if (!se->sum_exec_runtime || p->state == TASK_WAKING)
- return true;
-
- return false;
+ return p->se.normalized;
}
static void detach_task_cfs_rq(struct task_struct *p)
@@ -8384,7 +8374,7 @@ static void detach_task_cfs_rq(struct ta
* cause 'unlimited' sleep bonus.
*/
place_entity(cfs_rq, se, 0);
- se->vruntime -= cfs_rq->min_vruntime;
+ normalize_entity(cfs_rq, se);
}
/* Catch up with the cfs_rq and remove our load when we leave */
@@ -8407,8 +8397,8 @@ static void attach_task_cfs_rq(struct ta
/* Synchronize task with its cfs_rq */
attach_entity_load_avg(cfs_rq, se);
- if (!vruntime_normalized(p))
- se->vruntime += cfs_rq->min_vruntime;
+ if (vruntime_normalized(p))
+ renormalize_entity(cfs_rq, se);
}
static void switched_from_fair(struct rq *rq, struct task_struct *p)