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SubjectRe: [RFC][PATCH 01/13] sched/deadline: Impose global limits on sched_attr::sched_period
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On 5/20/20 8:38 PM, Juri Lelli wrote:
> Hi Peter,
>
> On 26/07/19 16:54, Peter Zijlstra wrote:
>> Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
>> Cc: Luca Abeni <luca.abeni@santannapisa.it>
>> Cc: Juri Lelli <juri.lelli@redhat.com>
>> Cc: Dmitry Vyukov <dvyukov@google.com>
>> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
>> ---
>> include/linux/sched/sysctl.h | 3 +++
>> kernel/sched/deadline.c | 23 +++++++++++++++++++++--
>> kernel/sysctl.c | 14 ++++++++++++++
>> 3 files changed, 38 insertions(+), 2 deletions(-)
>>
>> --- a/include/linux/sched/sysctl.h
>> +++ b/include/linux/sched/sysctl.h
>> @@ -56,6 +56,9 @@ int sched_proc_update_handler(struct ctl
>> extern unsigned int sysctl_sched_rt_period;
>> extern int sysctl_sched_rt_runtime;
>>
>> +extern unsigned int sysctl_sched_dl_period_max;
>> +extern unsigned int sysctl_sched_dl_period_min;
>> +
>> #ifdef CONFIG_UCLAMP_TASK
>> extern unsigned int sysctl_sched_uclamp_util_min;
>> extern unsigned int sysctl_sched_uclamp_util_max;
>> --- a/kernel/sched/deadline.c
>> +++ b/kernel/sched/deadline.c
>> @@ -2597,6 +2597,14 @@ void __getparam_dl(struct task_struct *p
>> }
>>
>> /*
>> + * Default limits for DL period; on the top end we guard against small util
>> + * tasks still getting rediculous long effective runtimes, on the bottom end we
>> + * guard against timer DoS.
>> + */
>> +unsigned int sysctl_sched_dl_period_max = 1 << 22; /* ~4 seconds */
>> +unsigned int sysctl_sched_dl_period_min = 100; /* 100 us */
>> +
>> +/*
>> * This function validates the new parameters of a -deadline task.
>> * We ask for the deadline not being zero, and greater or equal
>> * than the runtime, as well as the period of being zero or
>> @@ -2608,6 +2616,8 @@ void __getparam_dl(struct task_struct *p
>> */
>> bool __checkparam_dl(const struct sched_attr *attr)
>> {
>> + u64 period, max, min;
>> +
>> /* special dl tasks don't actually use any parameter */
>> if (attr->sched_flags & SCHED_FLAG_SUGOV)
>> return true;
>> @@ -2631,12 +2641,21 @@ bool __checkparam_dl(const struct sched_
>> attr->sched_period & (1ULL << 63))
>> return false;
>>
>> + period = attr->sched_period;
>> + if (!period)
>> + period = attr->sched_deadline;
>> +
>> /* runtime <= deadline <= period (if period != 0) */
>> - if ((attr->sched_period != 0 &&
>> - attr->sched_period < attr->sched_deadline) ||
>> + if (period < attr->sched_deadline ||
>> attr->sched_deadline < attr->sched_runtime)
>> return false;
>>
>> + max = (u64)READ_ONCE(sysctl_sched_dl_period_max) * NSEC_PER_USEC;
>> + min = (u64)READ_ONCE(sysctl_sched_dl_period_min) * NSEC_PER_USEC;
>> +
>> + if (period < min || period > max)
>> + return false;
>> +
>> return true;
>> }
>>
>> --- a/kernel/sysctl.c
>> +++ b/kernel/sysctl.c
>> @@ -443,6 +443,20 @@ static struct ctl_table kern_table[] = {
>> .proc_handler = sched_rt_handler,
>> },
>> {
>> + .procname = "sched_deadline_period_max_us",
>> + .data = &sysctl_sched_dl_period_max,
>> + .maxlen = sizeof(unsigned int),
>> + .mode = 0644,
>> + .proc_handler = proc_dointvec,
>> + },
>> + {
>> + .procname = "sched_deadline_period_min_us",
>> + .data = &sysctl_sched_dl_period_min,
>> + .maxlen = sizeof(unsigned int),
>> + .mode = 0644,
>> + .proc_handler = proc_dointvec,
>> + },
>> + {
>> .procname = "sched_rr_timeslice_ms",
>> .data = &sysctl_sched_rr_timeslice,
>> .maxlen = sizeof(int),
> I think this never made it upstream. And I believe both me and Daniel
> were OK with it. Do you recall if any additional change was needed?

Just to confirm, yes I am OK with it!

-- Daniel

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