Accumulate unused quota from previous periods, thus accumulated
bandwidth runtime can be used in the following periods. During
accumulation, take care of runtime overflow. Previous non-burstable
CFS bandwidth controller only assign quota to runtime, that saves a lot.
A sysctl parameter sysctl_sched_cfs_bw_burst_onset_percent is introduced to
denote how many percent of burst is given on setting cfs bandwidth. By
default it is 0, which means on burst is allowed unless accumulated.
Also, parameter sysctl_sched_cfs_bw_burst_enabled is introduced as a
switch for burst. It is enabled by default.
Signed-off-by: Huaixin Chang <[email protected]>
Signed-off-by: Shanpei Chen <[email protected]>
Reported-by: kernel test robot <[email protected]>
---
include/linux/sched/sysctl.h | 2 ++
kernel/sched/core.c | 31 +++++++++++++++++++++++++----
kernel/sched/fair.c | 47 ++++++++++++++++++++++++++++++++++++--------
kernel/sched/sched.h | 4 ++--
kernel/sysctl.c | 18 +++++++++++++++++
5 files changed, 88 insertions(+), 14 deletions(-)
diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h
index 3c31ba88aca5..3400828eaf2d 100644
--- a/include/linux/sched/sysctl.h
+++ b/include/linux/sched/sysctl.h
@@ -72,6 +72,8 @@ extern unsigned int sysctl_sched_uclamp_util_min_rt_default;
#ifdef CONFIG_CFS_BANDWIDTH
extern unsigned int sysctl_sched_cfs_bandwidth_slice;
+extern unsigned int sysctl_sched_cfs_bw_burst_onset_percent;
+extern unsigned int sysctl_sched_cfs_bw_burst_enabled;
#endif
#ifdef CONFIG_SCHED_AUTOGROUP
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 48d3bad12be2..fecf0f05ef0c 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -66,6 +66,16 @@ const_debug unsigned int sysctl_sched_features =
*/
const_debug unsigned int sysctl_sched_nr_migrate = 32;
+#ifdef CONFIG_CFS_BANDWIDTH
+/*
+ * Percent of burst assigned to cfs_b->runtime on tg_set_cfs_bandwidth,
+ * 0 by default.
+ */
+unsigned int sysctl_sched_cfs_bw_burst_onset_percent;
+
+unsigned int sysctl_sched_cfs_bw_burst_enabled = 1;
+#endif
+
/*
* period over which we measure -rt task CPU usage in us.
* default: 1s
@@ -7891,7 +7901,7 @@ static DEFINE_MUTEX(cfs_constraints_mutex);
const u64 max_cfs_quota_period = 1 * NSEC_PER_SEC; /* 1s */
static const u64 min_cfs_quota_period = 1 * NSEC_PER_MSEC; /* 1ms */
/* More than 203 days if BW_SHIFT equals 20. */
-static const u64 max_cfs_runtime = MAX_BW * NSEC_PER_USEC;
+const u64 max_cfs_runtime = MAX_BW * NSEC_PER_USEC;
static int __cfs_schedulable(struct task_group *tg, u64 period, u64 runtime);
@@ -7900,7 +7910,7 @@ static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota,
{
int i, ret = 0, runtime_enabled, runtime_was_enabled;
struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
- u64 buffer;
+ u64 buffer, burst_onset;
if (tg == &root_task_group)
return -EINVAL;
@@ -7961,11 +7971,24 @@ static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota,
cfs_b->burst = burst;
cfs_b->buffer = buffer;
- __refill_cfs_bandwidth_runtime(cfs_b);
+ cfs_b->max_overrun = DIV_ROUND_UP_ULL(max_cfs_runtime, quota);
+ cfs_b->runtime = cfs_b->quota;
+
+ /* burst_onset needed */
+ if (cfs_b->quota != RUNTIME_INF &&
+ sysctl_sched_cfs_bw_burst_enabled &&
+ sysctl_sched_cfs_bw_burst_onset_percent > 0) {
+
+ burst_onset = do_div(burst, 100) *
+ sysctl_sched_cfs_bw_burst_onset_percent;
+
+ cfs_b->runtime += burst_onset;
+ cfs_b->runtime = min(max_cfs_runtime, cfs_b->runtime);
+ }
/* Restart the period timer (if active) to handle new period expiry: */
if (runtime_enabled)
- start_cfs_bandwidth(cfs_b);
+ start_cfs_bandwidth(cfs_b, 1);
raw_spin_unlock_irq(&cfs_b->lock);
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 6bb4f89259fd..abe6eb05fe09 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4598,10 +4598,23 @@ static inline u64 sched_cfs_bandwidth_slice(void)
*
* requires cfs_b->lock
*/
-void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
+static void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b,
+ u64 overrun)
{
- if (cfs_b->quota != RUNTIME_INF)
- cfs_b->runtime = cfs_b->quota;
+ u64 refill;
+
+ if (cfs_b->quota != RUNTIME_INF) {
+
+ if (!sysctl_sched_cfs_bw_burst_enabled) {
+ cfs_b->runtime = cfs_b->quota;
+ return;
+ }
+
+ overrun = min(overrun, cfs_b->max_overrun);
+ refill = cfs_b->quota * overrun;
+ cfs_b->runtime += refill;
+ cfs_b->runtime = min(cfs_b->runtime, cfs_b->buffer);
+ }
}
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
@@ -4623,7 +4636,7 @@ static int __assign_cfs_rq_runtime(struct cfs_bandwidth *cfs_b,
if (cfs_b->quota == RUNTIME_INF)
amount = min_amount;
else {
- start_cfs_bandwidth(cfs_b);
+ start_cfs_bandwidth(cfs_b, 0);
if (cfs_b->runtime > 0) {
amount = min(cfs_b->runtime, min_amount);
@@ -4957,7 +4970,7 @@ static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun, u
if (cfs_b->idle && !throttled)
goto out_deactivate;
- __refill_cfs_bandwidth_runtime(cfs_b);
+ __refill_cfs_bandwidth_runtime(cfs_b, overrun);
if (!throttled) {
/* mark as potentially idle for the upcoming period */
@@ -5181,6 +5194,7 @@ static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
}
extern const u64 max_cfs_quota_period;
+extern const u64 max_cfs_runtime;
static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
{
@@ -5210,7 +5224,14 @@ static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
new = old * 2;
if (new < max_cfs_quota_period) {
cfs_b->period = ns_to_ktime(new);
- cfs_b->quota *= 2;
+ cfs_b->quota = min(cfs_b->quota * 2,
+ max_cfs_runtime);
+
+ cfs_b->buffer = min(max_cfs_runtime,
+ cfs_b->quota + cfs_b->burst);
+ /* Add 1 in case max_overrun becomes 0. */
+ cfs_b->max_overrun >>= 1;
+ cfs_b->max_overrun++;
pr_warn_ratelimited(
"cfs_period_timer[cpu%d]: period too short, scaling up (new cfs_period_us = %lld, cfs_quota_us = %lld)\n",
@@ -5259,16 +5280,26 @@ static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
INIT_LIST_HEAD(&cfs_rq->throttled_list);
}
-void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
+void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b, int init)
{
+ u64 overrun;
+
lockdep_assert_held(&cfs_b->lock);
if (cfs_b->period_active)
return;
cfs_b->period_active = 1;
- hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
+ overrun = hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
+
+ /*
+ * When period timer stops, quota for the following period is not
+ * refilled, however period timer is already forwarded. We should
+ * accumulate quota once more than overrun here.
+ */
+ if (!init)
+ __refill_cfs_bandwidth_runtime(cfs_b, overrun + 1);
}
static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index a8772eca8cbb..ff8b5382485d 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -366,6 +366,7 @@ struct cfs_bandwidth {
u64 runtime;
u64 burst;
u64 buffer;
+ u64 max_overrun;
s64 hierarchical_quota;
u8 idle;
@@ -476,8 +477,7 @@ extern void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
struct sched_entity *parent);
extern void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b);
-extern void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b);
-extern void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b);
+extern void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b, int init);
extern void unthrottle_cfs_rq(struct cfs_rq *cfs_rq);
extern void free_rt_sched_group(struct task_group *tg);
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index afad085960b8..291dca62a571 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1842,6 +1842,24 @@ static struct ctl_table kern_table[] = {
.proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ONE,
},
+ {
+ .procname = "sched_cfs_bw_burst_onset_percent",
+ .data = &sysctl_sched_cfs_bw_burst_onset_percent,
+ .maxlen = sizeof(unsigned int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = SYSCTL_ZERO,
+ .extra2 = &one_hundred,
+ },
+ {
+ .procname = "sched_cfs_bw_burst_enabled",
+ .data = &sysctl_sched_cfs_bw_burst_enabled,
+ .maxlen = sizeof(unsigned int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = SYSCTL_ZERO,
+ .extra2 = SYSCTL_ONE,
+ },
#endif
#if defined(CONFIG_ENERGY_MODEL) && defined(CONFIG_CPU_FREQ_GOV_SCHEDUTIL)
{
--
2.14.4.44.g2045bb6
On Thu, Jan 21, 2021 at 07:04:51PM +0800, Huaixin Chang wrote:
> Accumulate unused quota from previous periods, thus accumulated
> bandwidth runtime can be used in the following periods. During
> accumulation, take care of runtime overflow. Previous non-burstable
> CFS bandwidth controller only assign quota to runtime, that saves a lot.
>
> A sysctl parameter sysctl_sched_cfs_bw_burst_onset_percent is introduced to
> denote how many percent of burst is given on setting cfs bandwidth. By
> default it is 0, which means on burst is allowed unless accumulated.
>
> Also, parameter sysctl_sched_cfs_bw_burst_enabled is introduced as a
> switch for burst. It is enabled by default.
>
> Signed-off-by: Huaixin Chang <[email protected]>
> Signed-off-by: Shanpei Chen <[email protected]>
Identical invalid SoB chain.
> Reported-by: kernel test robot <[email protected]>
What exactly did the robot report; the whole patch?
> ---
> include/linux/sched/sysctl.h | 2 ++
> kernel/sched/core.c | 31 +++++++++++++++++++++++++----
> kernel/sched/fair.c | 47 ++++++++++++++++++++++++++++++++++++--------
> kernel/sched/sched.h | 4 ++--
> kernel/sysctl.c | 18 +++++++++++++++++
> 5 files changed, 88 insertions(+), 14 deletions(-)
>
> diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h
> index 3c31ba88aca5..3400828eaf2d 100644
> --- a/include/linux/sched/sysctl.h
> +++ b/include/linux/sched/sysctl.h
> @@ -72,6 +72,8 @@ extern unsigned int sysctl_sched_uclamp_util_min_rt_default;
>
> #ifdef CONFIG_CFS_BANDWIDTH
> extern unsigned int sysctl_sched_cfs_bandwidth_slice;
> +extern unsigned int sysctl_sched_cfs_bw_burst_onset_percent;
> +extern unsigned int sysctl_sched_cfs_bw_burst_enabled;
> #endif
>
> #ifdef CONFIG_SCHED_AUTOGROUP
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 48d3bad12be2..fecf0f05ef0c 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -66,6 +66,16 @@ const_debug unsigned int sysctl_sched_features =
> */
> const_debug unsigned int sysctl_sched_nr_migrate = 32;
>
> +#ifdef CONFIG_CFS_BANDWIDTH
> +/*
> + * Percent of burst assigned to cfs_b->runtime on tg_set_cfs_bandwidth,
> + * 0 by default.
> + */
> +unsigned int sysctl_sched_cfs_bw_burst_onset_percent;
> +
> +unsigned int sysctl_sched_cfs_bw_burst_enabled = 1;
> +#endif
There's already an #ifdef block that contains that bandwidth_slice
thing, see the previous hunk, so why create a new #ifdef here?
Also, personally I think percentages are over-represented as members of
Q.
> @@ -7891,7 +7901,7 @@ static DEFINE_MUTEX(cfs_constraints_mutex);
> const u64 max_cfs_quota_period = 1 * NSEC_PER_SEC; /* 1s */
> static const u64 min_cfs_quota_period = 1 * NSEC_PER_MSEC; /* 1ms */
> /* More than 203 days if BW_SHIFT equals 20. */
> -static const u64 max_cfs_runtime = MAX_BW * NSEC_PER_USEC;
> +const u64 max_cfs_runtime = MAX_BW * NSEC_PER_USEC;
>
> static int __cfs_schedulable(struct task_group *tg, u64 period, u64 runtime);
>
> @@ -7900,7 +7910,7 @@ static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota,
> {
> int i, ret = 0, runtime_enabled, runtime_was_enabled;
> struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
> - u64 buffer;
> + u64 buffer, burst_onset;
>
> if (tg == &root_task_group)
> return -EINVAL;
> @@ -7961,11 +7971,24 @@ static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota,
> cfs_b->burst = burst;
> cfs_b->buffer = buffer;
>
> - __refill_cfs_bandwidth_runtime(cfs_b);
> + cfs_b->max_overrun = DIV_ROUND_UP_ULL(max_cfs_runtime, quota);
> + cfs_b->runtime = cfs_b->quota;
> +
> + /* burst_onset needed */
> + if (cfs_b->quota != RUNTIME_INF &&
> + sysctl_sched_cfs_bw_burst_enabled &&
> + sysctl_sched_cfs_bw_burst_onset_percent > 0) {
'creative' indentation again...
Also, this gives rise to the question as to why onset_percent is
separate from enabled.
> +
> + burst_onset = do_div(burst, 100) *
> + sysctl_sched_cfs_bw_burst_onset_percent;
and again..
> +
> + cfs_b->runtime += burst_onset;
> + cfs_b->runtime = min(max_cfs_runtime, cfs_b->runtime);
> + }
>
> /* Restart the period timer (if active) to handle new period expiry: */
> if (runtime_enabled)
> - start_cfs_bandwidth(cfs_b);
> + start_cfs_bandwidth(cfs_b, 1);
>
> raw_spin_unlock_irq(&cfs_b->lock);
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 6bb4f89259fd..abe6eb05fe09 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4598,10 +4598,23 @@ static inline u64 sched_cfs_bandwidth_slice(void)
> *
> * requires cfs_b->lock
> */
> -void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
> +static void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b,
> + u64 overrun)
> {
> - if (cfs_b->quota != RUNTIME_INF)
> - cfs_b->runtime = cfs_b->quota;
> + u64 refill;
> +
> + if (cfs_b->quota != RUNTIME_INF) {
> +
> + if (!sysctl_sched_cfs_bw_burst_enabled) {
> + cfs_b->runtime = cfs_b->quota;
> + return;
> + }
> +
> + overrun = min(overrun, cfs_b->max_overrun);
> + refill = cfs_b->quota * overrun;
> + cfs_b->runtime += refill;
> + cfs_b->runtime = min(cfs_b->runtime, cfs_b->buffer);
> + }
> }
>
> static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
> @@ -4623,7 +4636,7 @@ static int __assign_cfs_rq_runtime(struct cfs_bandwidth *cfs_b,
> if (cfs_b->quota == RUNTIME_INF)
> amount = min_amount;
> else {
> - start_cfs_bandwidth(cfs_b);
> + start_cfs_bandwidth(cfs_b, 0);
>
> if (cfs_b->runtime > 0) {
> amount = min(cfs_b->runtime, min_amount);
> @@ -4957,7 +4970,7 @@ static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun, u
> if (cfs_b->idle && !throttled)
> goto out_deactivate;
>
> - __refill_cfs_bandwidth_runtime(cfs_b);
> + __refill_cfs_bandwidth_runtime(cfs_b, overrun);
>
> if (!throttled) {
> /* mark as potentially idle for the upcoming period */
> @@ -5181,6 +5194,7 @@ static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
> }
>
> extern const u64 max_cfs_quota_period;
> +extern const u64 max_cfs_runtime;
>
> static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
> {
> @@ -5210,7 +5224,14 @@ static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
> new = old * 2;
> if (new < max_cfs_quota_period) {
> cfs_b->period = ns_to_ktime(new);
> - cfs_b->quota *= 2;
> + cfs_b->quota = min(cfs_b->quota * 2,
> + max_cfs_runtime);
again, broken indent
> +
> + cfs_b->buffer = min(max_cfs_runtime,
> + cfs_b->quota + cfs_b->burst);
and again..
> + /* Add 1 in case max_overrun becomes 0. */
A better comment would explain *why* 0 is a problem; and possibly
include a reference to the code that cares
(__refill_cfs_bandiwdth_runtime() afaict).
> + cfs_b->max_overrun >>= 1;
> + cfs_b->max_overrun++;
>
> pr_warn_ratelimited(
> "cfs_period_timer[cpu%d]: period too short, scaling up (new cfs_period_us = %lld, cfs_quota_us = %lld)\n",
> On Mar 10, 2021, at 9:04 PM, Peter Zijlstra <[email protected]> wrote:
>
> On Thu, Jan 21, 2021 at 07:04:51PM +0800, Huaixin Chang wrote:
>> Accumulate unused quota from previous periods, thus accumulated
>> bandwidth runtime can be used in the following periods. During
>> accumulation, take care of runtime overflow. Previous non-burstable
>> CFS bandwidth controller only assign quota to runtime, that saves a lot.
>>
>> A sysctl parameter sysctl_sched_cfs_bw_burst_onset_percent is introduced to
>> denote how many percent of burst is given on setting cfs bandwidth. By
>> default it is 0, which means on burst is allowed unless accumulated.
>>
>> Also, parameter sysctl_sched_cfs_bw_burst_enabled is introduced as a
>> switch for burst. It is enabled by default.
>>
>> Signed-off-by: Huaixin Chang <[email protected]>
>> Signed-off-by: Shanpei Chen <[email protected]>
>
> Identical invalid SoB chain.
>
>> Reported-by: kernel test robot <[email protected]>
>
> What exactly did the robot report; the whole patch?
A warning is reported by the robot. And I have fixed it in this series. I'll remove this line,
since it seems unnecessary.
>
>> ---
>> include/linux/sched/sysctl.h | 2 ++
>> kernel/sched/core.c | 31 +++++++++++++++++++++++++----
>> kernel/sched/fair.c | 47 ++++++++++++++++++++++++++++++++++++--------
>> kernel/sched/sched.h | 4 ++--
>> kernel/sysctl.c | 18 +++++++++++++++++
>> 5 files changed, 88 insertions(+), 14 deletions(-)
>>
>> diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h
>> index 3c31ba88aca5..3400828eaf2d 100644
>> --- a/include/linux/sched/sysctl.h
>> +++ b/include/linux/sched/sysctl.h
>> @@ -72,6 +72,8 @@ extern unsigned int sysctl_sched_uclamp_util_min_rt_default;
>>
>> #ifdef CONFIG_CFS_BANDWIDTH
>> extern unsigned int sysctl_sched_cfs_bandwidth_slice;
>> +extern unsigned int sysctl_sched_cfs_bw_burst_onset_percent;
>> +extern unsigned int sysctl_sched_cfs_bw_burst_enabled;
>> #endif
>>
>> #ifdef CONFIG_SCHED_AUTOGROUP
>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>> index 48d3bad12be2..fecf0f05ef0c 100644
>> --- a/kernel/sched/core.c
>> +++ b/kernel/sched/core.c
>> @@ -66,6 +66,16 @@ const_debug unsigned int sysctl_sched_features =
>> */
>> const_debug unsigned int sysctl_sched_nr_migrate = 32;
>>
>> +#ifdef CONFIG_CFS_BANDWIDTH
>> +/*
>> + * Percent of burst assigned to cfs_b->runtime on tg_set_cfs_bandwidth,
>> + * 0 by default.
>> + */
>> +unsigned int sysctl_sched_cfs_bw_burst_onset_percent;
>> +
>> +unsigned int sysctl_sched_cfs_bw_burst_enabled = 1;
>> +#endif
>
> There's already an #ifdef block that contains that bandwidth_slice
> thing, see the previous hunk, so why create a new #ifdef here?
>
> Also, personally I think percentages are over-represented as members of
> Q.
>
Sorry, I don't quite understand the "members of Q". Is this saying that the percentages
are over-designed here?
>> @@ -7891,7 +7901,7 @@ static DEFINE_MUTEX(cfs_constraints_mutex);
>> const u64 max_cfs_quota_period = 1 * NSEC_PER_SEC; /* 1s */
>> static const u64 min_cfs_quota_period = 1 * NSEC_PER_MSEC; /* 1ms */
>> /* More than 203 days if BW_SHIFT equals 20. */
>> -static const u64 max_cfs_runtime = MAX_BW * NSEC_PER_USEC;
>> +const u64 max_cfs_runtime = MAX_BW * NSEC_PER_USEC;
>>
>> static int __cfs_schedulable(struct task_group *tg, u64 period, u64 runtime);
>>
>> @@ -7900,7 +7910,7 @@ static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota,
>> {
>> int i, ret = 0, runtime_enabled, runtime_was_enabled;
>> struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
>> - u64 buffer;
>> + u64 buffer, burst_onset;
>>
>> if (tg == &root_task_group)
>> return -EINVAL;
>> @@ -7961,11 +7971,24 @@ static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota,
>> cfs_b->burst = burst;
>> cfs_b->buffer = buffer;
>>
>> - __refill_cfs_bandwidth_runtime(cfs_b);
>> + cfs_b->max_overrun = DIV_ROUND_UP_ULL(max_cfs_runtime, quota);
>> + cfs_b->runtime = cfs_b->quota;
>> +
>> + /* burst_onset needed */
>> + if (cfs_b->quota != RUNTIME_INF &&
>> + sysctl_sched_cfs_bw_burst_enabled &&
>> + sysctl_sched_cfs_bw_burst_onset_percent > 0) {
>
> 'creative' indentation again...
>
> Also, this gives rise to the question as to why onset_percent is
> separate from enabled.
Odin noticed the precent thing, too. Maybe I will remove this and let cfsb start with 0 burst.
In this way, this if statement can be removed too.
>
>> +
>> + burst_onset = do_div(burst, 100) *
>> + sysctl_sched_cfs_bw_burst_onset_percent;
>
> and again..
>
>> +
>> + cfs_b->runtime += burst_onset;
>> + cfs_b->runtime = min(max_cfs_runtime, cfs_b->runtime);
>> + }
>>
>> /* Restart the period timer (if active) to handle new period expiry: */
>> if (runtime_enabled)
>> - start_cfs_bandwidth(cfs_b);
>> + start_cfs_bandwidth(cfs_b, 1);
>>
>> raw_spin_unlock_irq(&cfs_b->lock);
>>
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index 6bb4f89259fd..abe6eb05fe09 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -4598,10 +4598,23 @@ static inline u64 sched_cfs_bandwidth_slice(void)
>> *
>> * requires cfs_b->lock
>> */
>> -void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
>> +static void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b,
>> + u64 overrun)
>> {
>> - if (cfs_b->quota != RUNTIME_INF)
>> - cfs_b->runtime = cfs_b->quota;
>> + u64 refill;
>> +
>> + if (cfs_b->quota != RUNTIME_INF) {
>> +
>> + if (!sysctl_sched_cfs_bw_burst_enabled) {
>> + cfs_b->runtime = cfs_b->quota;
>> + return;
>> + }
>> +
>> + overrun = min(overrun, cfs_b->max_overrun);
>> + refill = cfs_b->quota * overrun;
>> + cfs_b->runtime += refill;
>> + cfs_b->runtime = min(cfs_b->runtime, cfs_b->buffer);
>> + }
>> }
>>
>> static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
>> @@ -4623,7 +4636,7 @@ static int __assign_cfs_rq_runtime(struct cfs_bandwidth *cfs_b,
>> if (cfs_b->quota == RUNTIME_INF)
>> amount = min_amount;
>> else {
>> - start_cfs_bandwidth(cfs_b);
>> + start_cfs_bandwidth(cfs_b, 0);
>>
>> if (cfs_b->runtime > 0) {
>> amount = min(cfs_b->runtime, min_amount);
>> @@ -4957,7 +4970,7 @@ static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun, u
>> if (cfs_b->idle && !throttled)
>> goto out_deactivate;
>>
>> - __refill_cfs_bandwidth_runtime(cfs_b);
>> + __refill_cfs_bandwidth_runtime(cfs_b, overrun);
>>
>> if (!throttled) {
>> /* mark as potentially idle for the upcoming period */
>> @@ -5181,6 +5194,7 @@ static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
>> }
>>
>> extern const u64 max_cfs_quota_period;
>> +extern const u64 max_cfs_runtime;
>>
>> static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
>> {
>> @@ -5210,7 +5224,14 @@ static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
>> new = old * 2;
>> if (new < max_cfs_quota_period) {
>> cfs_b->period = ns_to_ktime(new);
>> - cfs_b->quota *= 2;
>> + cfs_b->quota = min(cfs_b->quota * 2,
>> + max_cfs_runtime);
>
> again, broken indent
>
>> +
>> + cfs_b->buffer = min(max_cfs_runtime,
>> + cfs_b->quota + cfs_b->burst);
>
> and again..
>
>> + /* Add 1 in case max_overrun becomes 0. */
>
> A better comment would explain *why* 0 is a problem; and possibly
> include a reference to the code that cares
> (__refill_cfs_bandiwdth_runtime() afaict).
>
>> + cfs_b->max_overrun >>= 1;
>> + cfs_b->max_overrun++;
>>
>> pr_warn_ratelimited(
>> "cfs_period_timer[cpu%d]: period too short, scaling up (new cfs_period_us = %lld, cfs_quota_us = %lld)\n",
On Fri, Mar 12, 2021 at 09:54:33PM +0800, changhuaixin wrote:
> > On Mar 10, 2021, at 9:04 PM, Peter Zijlstra <[email protected]> wrote:
> > There's already an #ifdef block that contains that bandwidth_slice
> > thing, see the previous hunk, so why create a new #ifdef here?
> >
> > Also, personally I think percentages are over-represented as members of
> > Q.
> >
> Sorry, I don't quite understand the "members of Q". Is this saying that the percentages
> are over-designed here?
You know the number groups (in order): N, Z, Q, R, C, H, O.
Percent being 1/100 is a fraction and thus part of Q (and anything
higher ofcourse).
Some people seem to think percent is magical and special. It's just a
fraction like the inifinite many others in Q. It's also a very crappy
one when we consider computers.
Basically I hate percentages, they're nothing special and often employed
where they should not be.