vchiq: Performance regression since 5.18-rc1

[Stefan Wahren]

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.

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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