Re: [RFC 3/6] Introduce static key to enable or disable TurboSched

[Parth Shah <parth015@linux.vnet.ibm.com>]

On 4/4/19 3:28 PM, Akshay Adiga wrote:
> On Mon, Mar 25, 2019 at 03:42:48PM -0700, Doug Smythies wrote:
>> On 2019.03.21 23:06 Parth Shah wrote:
>>
>>> Signed-off-by: Parth Shah <parth015@linux.vnet.ibm.com>
>>> ---
>>>  kernel/sched/core.c  | 36 ++++++++++++++++++++++++++++++++++++
>>> kernel/sched/fair.c  |  2 +-
>>> kernel/sched/sched.h |  7 +++++++
>>> 3 files changed, 44 insertions(+), 1 deletion(-)
>>
>> ...[snip]...
>>
>> I wanted to try this patch set with a particular work flow.
>> I actually don't think it will help, but wanted to try it.
>>
>> Forgive me if this is something that should be obvious but...
>>
>> I have not been able to figure out how to enable or disable
>> Turboshed.
>>
>> This patch suggests that I should be able to, but how?
>>
>> I have a kernel 5.1-rc1 with this entire patch set added.
>>  
>> ... Doug
>>
>>
> I think he added attribute called cpu.turbo_sched for each cpu controller.
> 
> In order to enable this feature you need first create a cpu cgroup, and set
> the attribute value cpu.turbo_sched to :
>   - cpu.turbo_sched = 1 (tasks benefiting from high freq) or
>   - cpu.turbo_sched = 2 (tasks which are jitters)
> 
> Looks like  the feature is disabled by default or cpu.turbo_sched = 0.
> 

Correct Akshay.

In fact, one can follow the below procedure to create 2 different categories
of workload,

cd  /sys/fs/cgroup/cpu/
mkdir type1
execute type1_workload
echo `pidof type1_workload` > type1/cgroup.procs && echo 1 > type1/cpu.turbo_sched
mkdir type2
execute type2_workload
echo `pidof type2_workload` > type2/cgroup.procs && echo 2 > type2/cpu.turbo_sched

where    Type1 = tasks benefiting from high freq
and    Type2 = tasks which are jitters


One can use the test benchmark (wofbench.c) to have a quick demo of TurboSched as follows

Execute program with 8 jitters and 8 High util tasks: wofbench -t 30 -h 8 -n 16
Create cgroup: cd  /sys/fs/cgroup/cpu/ && mkdir type2
Put task: echo `pidof wofbench`> type2/cgroup.procs && echo 2 > type2/cpu.turbo_sched
Result: Jitters will be packed on the same core as other 8 High util tasks.

Thus during multi-thread workload execution, if the system throttles frequency
due to power budget constraint of the system, using these patches may result in
sustaining of higher frequencies by keeping maximum cores idle.

Hope this helps. Thanks