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SubjectRe: [Question]: try to fix contention between expire_timers and try_to_del_timer_sync

Hi Qiao,


On 2017-08-01 00:37, qiaozhou wrote:
> On 2017年07月31日 19:20, qiaozhou wrote:
>>
>>

<snip>

>>> =====================================================
>>> Also apply Vikram's patch and have a test.
>
> cpu2: a53, 832MHz, cpu7: a73, 1.75Hz
> Without cpu_relax bodging patch
> =====================================================
> cpu2 time | cpu2 counter | cpu7 time | cpu7 counter |
> ==========|==============|===========|==============|
> 16505| 5243| 2| 12487322|
> 16494| 5619| 1| 12013291|
> 16498| 5276| 2| 11706824|
> 16494| 7123| 1| 12532355|
> 16470| 7208| 2| 11784617|
> =====================================================
>
> cpu2: a53, 832MHz, cpu7: a73, 1.75Hz
> With cpu_relax bodging patch:
> =====================================================
> cpu2 time | cpu2 counter | cpu7 time | cpu7 counter |
> ==========|==============|===========|==============|
> 3991| 140714| 1| 11430528|
> 4018| 144371| 1| 11430528|
> 4034| 143250| 1| 11427011|
> 4330| 147345| 1| 11423583|
> 4752| 138273| 1| 11433241|
> =====================================================
>
> It has some improvements, but not so good as Vikram's data. The big
> core still has much more chance to acquire lock.
>>>
>>> Thanks,
>>> Vikram
>>>

Thanks for your data! I'll check on one of our other platforms to see
if I see similar behavior. This may have something to do with the
event-stream on your platform or the A53 revision as Sudeep pointed
out here [1] - something to check I suppose...

Thanks,
Vikram

[1] - https://lkml.org/lkml/2016/11/21/458

--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

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