Re: [RFC PATCH 0/3] Add a new flag for ITS device to control indirect route

Marc Zyngier
2016-12-02T09:35:14Z

On 02/12/16 09:29, majun (Euler7) wrote:
>
>
> 在 2016/12/1 17:07, Marc Zyngier 写道:
>> On 01/12/16 07:45, Majun wrote:
>>> From: MaJun <majun258@huawei.com>
>>>
>>> For current ITS driver, two level table (indirect route) is enabled when the memory used
>>> for LPI route table over the limit(64KB * 2) size. But this function impact the
>>> performance of LPI interrupt actually because need more time to look up the table.
>>
>> Are you implying that your ITS doesn't have a cache to lookup the most
>> active devices, hence performing a full lookup on each interrupt?
>
> Our ITS chip has the cache with depth 64. But this seems not enough for some
> scenario,espeically on virtulization platform.

Then I don't see how switching to to flat tables is going to improve
things. Can you share actual performance numbers?

>> Anyway, doing this as a DT quirk doesn't feel right. Please use the ITS
>> quirk infrastructure.
>
> If there is no other better solutions, I will do this.

Thanks,

M.
--
Jazz is not dead. It just smells funny...