* [PATCH] sched/fair: sanitize vruntime of entity being migrated
@ 2023-03-04 8:29 Zhang Qiao
2023-03-06 11:12 ` Vincent Guittot
0 siblings, 1 reply; 3+ messages in thread
From: Zhang Qiao @ 2023-03-04 8:29 UTC (permalink / raw)
To: lkml
Cc: Valentin Schneider, Zhang Qiao, Ben Segall, Vincent Guittot,
Waiman Long, Peter Zijlstra, Steven Rostedt, Mel Gorman,
Dietmar Eggemann, Daniel Bristot de Oliveira, Ingo Molnar,
Juri Lelli
Commit 829c1651e9c4 ("sched/fair: sanitize vruntime of
entity being placed") fix an overflowing bug, but ignore
a case that se->exec_start is reset after a migration.
For fix this case, we reset the vruntime of a loog sleep
task in migrate_task_rq_fair().
Fixes: 829c1651e9c4 ("sched/fair: sanitize vruntime of entity being placed")
Suggested-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Zhang Qiao <zhangqiao22@huawei.com>
---
kernel/sched/fair.c | 73 ++++++++++++++++++++++++++++++++-------------
1 file changed, 53 insertions(+), 20 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index ff4dbbae3b10..6697462baf0f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4648,6 +4648,41 @@ static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
#endif
}
+static inline bool entity_is_long_sleep(struct sched_entity *se)
+{
+ struct cfs_rq *cfs_rq;
+ u64 sleep_time;
+
+ if (se->exec_start == 0)
+ return false;
+
+ cfs_rq = cfs_rq_of(se);
+ sleep_time = rq_clock_task(rq_of(cfs_rq)) - se->exec_start;
+ if ((s64)sleep_time > 60LL * NSEC_PER_SEC)
+ return true;
+
+ return false;
+}
+
+static inline u64 sched_sleeper_credit(struct sched_entity *se)
+{
+ unsigned long thresh;
+
+ if (se_is_idle(se))
+ thresh = sysctl_sched_min_granularity;
+ else
+ thresh = sysctl_sched_latency;
+
+ /*
+ * Halve their sleep time's effect, to allow
+ * for a gentler effect of sleepers:
+ */
+ if (sched_feat(GENTLE_FAIR_SLEEPERS))
+ thresh >>= 1;
+
+ return thresh;
+}
+
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
@@ -4664,23 +4699,8 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
vruntime += sched_vslice(cfs_rq, se);
/* sleeps up to a single latency don't count. */
- if (!initial) {
- unsigned long thresh;
-
- if (se_is_idle(se))
- thresh = sysctl_sched_min_granularity;
- else
- thresh = sysctl_sched_latency;
-
- /*
- * Halve their sleep time's effect, to allow
- * for a gentler effect of sleepers:
- */
- if (sched_feat(GENTLE_FAIR_SLEEPERS))
- thresh >>= 1;
-
- vruntime -= thresh;
- }
+ if (!initial)
+ vruntime -= sched_sleeper_credit(se);
/*
* Pull vruntime of the entity being placed to the base level of
@@ -4689,8 +4709,7 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
* the base as it may be too far off and the comparison may get
* inversed due to s64 overflow.
*/
- sleep_time = rq_clock_task(rq_of(cfs_rq)) - se->exec_start;
- if ((s64)sleep_time > 60LL * NSEC_PER_SEC)
+ if (entity_is_long_sleep(se))
se->vruntime = vruntime;
else
se->vruntime = max_vruntime(se->vruntime, vruntime);
@@ -7635,7 +7654,21 @@ static void migrate_task_rq_fair(struct task_struct *p, int new_cpu)
if (READ_ONCE(p->__state) == TASK_WAKING) {
struct cfs_rq *cfs_rq = cfs_rq_of(se);
- se->vruntime -= u64_u32_load(cfs_rq->min_vruntime);
+ /*
+ * We determine a task whether sleep for long by checking se->exec_start,
+ * and if it is, sanitize its vruntime at place_entity(). However, after
+ * a migration, this detection method fails due to se->exec_start is reset.
+ *
+ * For fix this case, we add the same check at here. For a task which has
+ * slept for long, its vruntime should be reset cfs_rq->min_vruntime and get
+ * a sleep credit. Because waking task's vruntime will be added cfs_rq->min_vruntime
+ * when enqueue, so we only need resetting the se->vruntime of waking task
+ * to a credit at here.
+ */
+ if (entity_is_long_sleep(se))
+ se->vruntime = -sched_sleeper_credit(se);
+ else
+ se->vruntime -= u64_u32_load(cfs_rq->min_vruntime);
}
if (!task_on_rq_migrating(p)) {
--
2.17.1
.
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] sched/fair: sanitize vruntime of entity being migrated
2023-03-04 8:29 [PATCH] sched/fair: sanitize vruntime of entity being migrated Zhang Qiao
@ 2023-03-06 11:12 ` Vincent Guittot
2023-03-06 12:26 ` Zhang Qiao
0 siblings, 1 reply; 3+ messages in thread
From: Vincent Guittot @ 2023-03-06 11:12 UTC (permalink / raw)
To: Zhang Qiao
Cc: lkml, Valentin Schneider, Ben Segall, Waiman Long,
Peter Zijlstra, Steven Rostedt, Mel Gorman, Dietmar Eggemann,
Daniel Bristot de Oliveira, Ingo Molnar, Juri Lelli
On Sat, 4 Mar 2023 at 09:29, Zhang Qiao <zhangqiao22@huawei.com> wrote:
>
> Commit 829c1651e9c4 ("sched/fair: sanitize vruntime of
> entity being placed") fix an overflowing bug, but ignore
> a case that se->exec_start is reset after a migration.
>
> For fix this case, we reset the vruntime of a loog sleep
> task in migrate_task_rq_fair().
some typo:
"For fixing this case, we reset the vruntime of a long sleeping task
in migrate_task_rq_fair()."
>
> Fixes: 829c1651e9c4 ("sched/fair: sanitize vruntime of entity being placed")
> Suggested-by: Vincent Guittot <vincent.guittot@linaro.org>
> Signed-off-by: Zhang Qiao <zhangqiao22@huawei.com>
Your patch doesn't apply. It seems to be malformed
> ---
> kernel/sched/fair.c | 73 ++++++++++++++++++++++++++++++++-------------
> 1 file changed, 53 insertions(+), 20 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index ff4dbbae3b10..6697462baf0f 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4648,6 +4648,41 @@ static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
> #endif
> }
> +static inline bool entity_is_long_sleep(struct sched_entity *se)
This extra space at the beg of the line above looks strange
> +{
> + struct cfs_rq *cfs_rq;
> + u64 sleep_time;
> +
> + if (se->exec_start == 0)
> + return false;
> +
> + cfs_rq = cfs_rq_of(se);
> + sleep_time = rq_clock_task(rq_of(cfs_rq)) - se->exec_start;
> + if ((s64)sleep_time > 60LL * NSEC_PER_SEC)
> + return true;
> +
> + return false;
> +}
> +
> +static inline u64 sched_sleeper_credit(struct sched_entity *se)
> +{
> + unsigned long thresh;
> +
> + if (se_is_idle(se))
> + thresh = sysctl_sched_min_granularity;
> + else
> + thresh = sysctl_sched_latency;
> +
> + /*
> + * Halve their sleep time's effect, to allow
> + * for a gentler effect of sleepers:
> + */
> + if (sched_feat(GENTLE_FAIR_SLEEPERS))
> + thresh >>= 1;
> +
> + return thresh;
> +}
> +
> static void
> place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
> {
> @@ -4664,23 +4699,8 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
> vruntime += sched_vslice(cfs_rq, se);
> /* sleeps up to a single latency don't count. */
> - if (!initial) {
> - unsigned long thresh;
> -
> - if (se_is_idle(se))
> - thresh = sysctl_sched_min_granularity;
> - else
> - thresh = sysctl_sched_latency;
> -
> - /*
> - * Halve their sleep time's effect, to allow
> - * for a gentler effect of sleepers:
> - */
> - if (sched_feat(GENTLE_FAIR_SLEEPERS))
> - thresh >>= 1;
> -
> - vruntime -= thresh;
> - }
> + if (!initial)
> + vruntime -= sched_sleeper_credit(se);
> /*
> * Pull vruntime of the entity being placed to the base level of
> @@ -4689,8 +4709,7 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
> * the base as it may be too far off and the comparison may get
> * inversed due to s64 overflow.
> */
> - sleep_time = rq_clock_task(rq_of(cfs_rq)) - se->exec_start;
> - if ((s64)sleep_time > 60LL * NSEC_PER_SEC)
> + if (entity_is_long_sleep(se))
> se->vruntime = vruntime;
> else
> se->vruntime = max_vruntime(se->vruntime, vruntime);
> @@ -7635,7 +7654,21 @@ static void migrate_task_rq_fair(struct task_struct *p, int new_cpu)
> if (READ_ONCE(p->__state) == TASK_WAKING) {
> struct cfs_rq *cfs_rq = cfs_rq_of(se);
> - se->vruntime -= u64_u32_load(cfs_rq->min_vruntime);
> + /*
> + * We determine a task whether sleep for long by checking se->exec_start,
> + * and if it is, sanitize its vruntime at place_entity(). However, after
> + * a migration, this detection method fails due to se->exec_start is reset.
some typo
"We determine whether a task sleeps for long by checking
se->exec_start, and if it is, we sanitize its vruntime at
place_entity(). However, after a migration, this detection method
fails due to se->exec_start being reset."
> + *
> + * For fix this case, we add the same check at here. For a task which has
> + * slept for long, its vruntime should be reset cfs_rq->min_vruntime and get
> + * a sleep credit. Because waking task's vruntime will be added cfs_rq->min_vruntime
For fixing this case, we add the same check here. For a task which has
slept for a long time, its vruntime should be reset to
cfs_rq->min_vruntime with a sleep credit.
Beside the typo and malformed patch, the proposed fix looks good to me
> + * when enqueue, so we only need resetting the se->vruntime of waking task
> + * to a credit at here.
> + */
> + if (entity_is_long_sleep(se))
> + se->vruntime = -sched_sleeper_credit(se);
> + else
> + se->vruntime -= u64_u32_load(cfs_rq->min_vruntime);
> }
> if (!task_on_rq_migrating(p)) {
> --
> 2.17.1
>
> .
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] sched/fair: sanitize vruntime of entity being migrated
2023-03-06 11:12 ` Vincent Guittot
@ 2023-03-06 12:26 ` Zhang Qiao
0 siblings, 0 replies; 3+ messages in thread
From: Zhang Qiao @ 2023-03-06 12:26 UTC (permalink / raw)
To: Vincent Guittot
Cc: lkml, Valentin Schneider, Ben Segall, Waiman Long,
Peter Zijlstra, Steven Rostedt, Mel Gorman, Dietmar Eggemann,
Daniel Bristot de Oliveira, Ingo Molnar, Juri Lelli
在 2023/3/6 19:12, Vincent Guittot 写道:
> On Sat, 4 Mar 2023 at 09:29, Zhang Qiao <zhangqiao22@huawei.com> wrote:
>>
>> Commit 829c1651e9c4 ("sched/fair: sanitize vruntime of
>> entity being placed") fix an overflowing bug, but ignore
>> a case that se->exec_start is reset after a migration.
>>
>> For fix this case, we reset the vruntime of a loog sleep
>> task in migrate_task_rq_fair().
>
> some typo:
> "For fixing this case, we reset the vruntime of a long sleeping task
> in migrate_task_rq_fair()."
>
>>
>> Fixes: 829c1651e9c4 ("sched/fair: sanitize vruntime of entity being placed")
>> Suggested-by: Vincent Guittot <vincent.guittot@linaro.org>
>> Signed-off-by: Zhang Qiao <zhangqiao22@huawei.com>
>
> Your patch doesn't apply. It seems to be malformed
>
>> ---
>> kernel/sched/fair.c | 73 ++++++++++++++++++++++++++++++++-------------
>> 1 file changed, 53 insertions(+), 20 deletions(-)
>>
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index ff4dbbae3b10..6697462baf0f 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -4648,6 +4648,41 @@ static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
>> #endif
>> }
>> +static inline bool entity_is_long_sleep(struct sched_entity *se)
>
> This extra space at the beg of the line above looks strange
>
>> +{
>> + struct cfs_rq *cfs_rq;
>> + u64 sleep_time;
>> +
>> + if (se->exec_start == 0)
>> + return false;
>> +
>> + cfs_rq = cfs_rq_of(se);
>> + sleep_time = rq_clock_task(rq_of(cfs_rq)) - se->exec_start;
>> + if ((s64)sleep_time > 60LL * NSEC_PER_SEC)
>> + return true;
>> +
>> + return false;
>> +}
>> +
>> +static inline u64 sched_sleeper_credit(struct sched_entity *se)
>> +{
>> + unsigned long thresh;
>> +
>> + if (se_is_idle(se))
>> + thresh = sysctl_sched_min_granularity;
>> + else
>> + thresh = sysctl_sched_latency;
>> +
>> + /*
>> + * Halve their sleep time's effect, to allow
>> + * for a gentler effect of sleepers:
>> + */
>> + if (sched_feat(GENTLE_FAIR_SLEEPERS))
>> + thresh >>= 1;
>> +
>> + return thresh;
>> +}
>> +
>> static void
>> place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
>> {
>> @@ -4664,23 +4699,8 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
>> vruntime += sched_vslice(cfs_rq, se);
>> /* sleeps up to a single latency don't count. */
>> - if (!initial) {
>> - unsigned long thresh;
>> -
>> - if (se_is_idle(se))
>> - thresh = sysctl_sched_min_granularity;
>> - else
>> - thresh = sysctl_sched_latency;
>> -
>> - /*
>> - * Halve their sleep time's effect, to allow
>> - * for a gentler effect of sleepers:
>> - */
>> - if (sched_feat(GENTLE_FAIR_SLEEPERS))
>> - thresh >>= 1;
>> -
>> - vruntime -= thresh;
>> - }
>> + if (!initial)
>> + vruntime -= sched_sleeper_credit(se);
>> /*
>> * Pull vruntime of the entity being placed to the base level of
>> @@ -4689,8 +4709,7 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
>> * the base as it may be too far off and the comparison may get
>> * inversed due to s64 overflow.
>> */
>> - sleep_time = rq_clock_task(rq_of(cfs_rq)) - se->exec_start;
>> - if ((s64)sleep_time > 60LL * NSEC_PER_SEC)
>> + if (entity_is_long_sleep(se))
>> se->vruntime = vruntime;
>> else
>> se->vruntime = max_vruntime(se->vruntime, vruntime);
>> @@ -7635,7 +7654,21 @@ static void migrate_task_rq_fair(struct task_struct *p, int new_cpu)
>> if (READ_ONCE(p->__state) == TASK_WAKING) {
>> struct cfs_rq *cfs_rq = cfs_rq_of(se);
>> - se->vruntime -= u64_u32_load(cfs_rq->min_vruntime);
>> + /*
>> + * We determine a task whether sleep for long by checking se->exec_start,
>> + * and if it is, sanitize its vruntime at place_entity(). However, after
>> + * a migration, this detection method fails due to se->exec_start is reset.
>
> some typo
>
> "We determine whether a task sleeps for long by checking
> se->exec_start, and if it is, we sanitize its vruntime at
> place_entity(). However, after a migration, this detection method
> fails due to se->exec_start being reset."
>
>> + *
>> + * For fix this case, we add the same check at here. For a task which has
>> + * slept for long, its vruntime should be reset cfs_rq->min_vruntime and get
>> + * a sleep credit. Because waking task's vruntime will be added cfs_rq->min_vruntime
>
> For fixing this case, we add the same check here. For a task which has
> slept for a long time, its vruntime should be reset to
> cfs_rq->min_vruntime with a sleep credit.
>
> Beside the typo and malformed patch, the proposed fix looks good to me
HI, Vincent,
Thank you for your correction.
>
>> + * when enqueue, so we only need resetting the se->vruntime of waking task
>> + * to a credit at here.
>> + */
>> + if (entity_is_long_sleep(se))
>> + se->vruntime = -sched_sleeper_credit(se);
>> + else
>> + se->vruntime -= u64_u32_load(cfs_rq->min_vruntime);
>> }
>> if (!task_on_rq_migrating(p)) {
>> --
>> 2.17.1
>>
>> .
> .
>
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2023-03-06 12:26 UTC | newest]
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2023-03-04 8:29 [PATCH] sched/fair: sanitize vruntime of entity being migrated Zhang Qiao
2023-03-06 11:12 ` Vincent Guittot
2023-03-06 12:26 ` Zhang Qiao
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