Re: [PATCH v5 08/12] sched: move cfs task on a CPU with higher capacity

[Vincent Guittot]

On 5 September 2014 14:06, Preeti U Murthy <preeti@xxxxxxxxxxxxxxxxxx> wrote:
> Hi Vincent,
>
> On 08/26/2014 04:36 PM, Vincent Guittot wrote:
>> If the CPU is used for handling lot of IRQs, trig a load balance to check if
>> it's worth moving its tasks on another CPU that has more capacity.
>>
>> As a sidenote, this will note generate more spurious ilb because we already
>> trig an ilb if there is more than 1 busy cpu. If this cpu is the only one that
>> has a task, we will trig the ilb once for migrating the task.
>>
>> The nohz_kick_needed function has been cleaned up a bit while adding the new
>> test
>>
>> Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
>
> So I see that there are added checks in your previous patches on if the
> cpu capacity for CFS tasks is good enough to run tasks on the cpu. My
> concern is although they appear sensible, would they trigger an increase
> in the number of times we load balance to a large extent.
>
> Ebizzy would not test this aspect right? There are no real time
> tasks/interrupts that get generated.

yes, ebizzy doesn't test this part but check for non regression

The scp test is the one that i use to check this patch and the
previous one but a test with some cfs and rt tasks should also do the
jobs.
we can see an increase of 82% for the dual core when
CONFIG_IRQ_TIME_ACCOUNTING is enable

>
> Besides, what is the column that says patchset+irq? What is the irq
> accounting patchset that you refer to in your cover letter?

it refers to CONFIG_IRQ_TIME_ACCOUNTING which includes the time spent
under interrupt context to compute the scale_rt_capacity

Regards,
Vincent

>
> Regards
> Preeti U Murthy
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/