vchiq: Performance regression since 5.18-rc1

[Stefan Wahren]

Am 25.05.22 um 17:37 schrieb Marcelo Tosatti:
> On Wed, May 25, 2022 at 04:07:47PM +0200, Stefan Wahren wrote:
>> Hi Marcelo,
>>
>> Am 25.05.22 um 15:56 schrieb Marcelo Tosatti:
>>> On Mon, May 23, 2022 at 09:09:07AM +0200, Sebastian Andrzej Siewior wrote:
>>>> On 2022-05-22 01:22:00 [+0200], Stefan Wahren wrote:
>>>>> Hi,
>>>> Hi,
>>>>
>>>>> while testing the staging/vc04_services/interface/vchiq_arm driver with my
>>>>> Raspberry Pi 3 B+ (multi_v7_defconfig) i noticed a huge performance
>>>>> regression since [ff042f4a9b050895a42cae893cc01fa2ca81b95c] mm:
>>>>> lru_cache_disable: replace work queue synchronization with synchronize_rcu
>>>>>
>>>>> Usually i run "vchiq_test -f 1" to see the driver is still working [1].
>>>> What about
>>>> 	https://lore.kernel.org/all/YmrWK%2FKoU1zrAxPI@fuller.cnet/
>>>>
>>>> Sebastian
>>> Stefan,
>>>
>>> Can you please try the patch above ?
>> this was the same as Paul send. I think i need more time for investigation,
>> maybe there is an issue with the application.
> To clarify: they are not the same patches.
Thanks for pointing out. I will test it ASAP.
>
>> All i noticed so far is that in good case the CPU usage is around ~ 60 % and
>> higher, while in bad case the CPU is almost idle. Also the issue is not
>> reproducible with arm64/defconfig.
>>
>>>
>>>
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>>