Subject: Re: [RFC PATCH 0/3] Add a new flag for ITS device to control indirect
 route
To: "majun (Euler7)" <majun258@huawei.com>, linux-kernel@vger.kernel.org,
        linux-acpi@vger.kernel.org, robert.moore@intel.com, lenb@kernel.org,
        lv.zheng@intel.com, rafael.j.wysocki@intel.com, devel@acpica.org,
        mark.rutland@arm.com, robh+dt@kernel.org, jason@lakedaemon.net
References: <1480578360-9268-1-git-send-email-majun258@huawei.com>
 <3ce161a7-ee63-a018-4a75-9e7520143d97@arm.com> <58413F0E.3030604@huawei.com>
Cc: dingtianhong@huawei.com, guohanjun@huawei.com
From: Marc Zyngier <marc.zyngier@arm.com>
Organization: ARM Ltd
Message-ID: <bd4114c2-a6d9-123c-8f9f-e6da33a481ba@arm.com>
Date: Fri, 2 Dec 2016 09:35:10 +0000
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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...