Re: [RFC][PATCH 01/13] sched/deadline: Impose global limits on sched_attr::sched_period

[Daniel Bristot de Oliveira <bristot@redhat.com>]

On 29/07/2019 10:57, Juri Lelli wrote:
> Hi,
> 
> 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
> s/rediculous/ridiculous/
> 
>> + * 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 */
> These limits look sane to me. I've actually been experimenting with 10us
> period tasks and throttling seemed to behave fine, but I guess 100us is
> a saner default.
> 
> So, (with a few lines of changelog :)
> 
> Acked-by: Juri Lelli <juri.lelli@redhat.com>


Looks sane to me too!

Acked-by: Daniel Bristot de Oliveira <bristot@redhat.com>

-- Daniel