Re: [PATCH] irqchip: gicv3-its: Use NUMA aware memory allocation for ITS tables

From: Ganapatrao Kulkarni
Date: Mon Jul 10 2017 - 05:08:46 EST

On Mon, Jul 10, 2017 at 2:36 PM, Marc Zyngier <marc.zyngier@xxxxxxx> wrote:
> On 10/07/17 09:48, Ganapatrao Kulkarni wrote:
>> Hi Marc,
>> On Mon, Jul 3, 2017 at 8:23 PM, Marc Zyngier <marc.zyngier@xxxxxxx> wrote:
>>> Hi Shanker,
>>> On 03/07/17 15:24, Shanker Donthineni wrote:
>>>> Hi Marc,
>>>> On 06/30/2017 03:51 AM, Marc Zyngier wrote:
>>>>> On 30/06/17 04:01, Ganapatrao Kulkarni wrote:
>>>>>> On Fri, Jun 30, 2017 at 8:04 AM, Ganapatrao Kulkarni
>>>>>> <gpkulkarni@xxxxxxxxx> wrote:
>>>>>>> Hi Shanker,
>>>>>>> On Sun, Jun 25, 2017 at 9:16 PM, Shanker Donthineni
>>>>>>> <shankerd@xxxxxxxxxxxxxx> wrote:
>>>>>>>> The NUMA node information is visible to ITS driver but not being used
>>>>>>>> other than handling errata. This patch allocates the memory for ITS
>>>>>>>> tables from the corresponding NUMA node using the appropriate NUMA
>>>>>>>> aware functions.
>>>>>> IMHO, the description would have been more constructive?
>>>>>> "All ITS tables are mapped by default to NODE 0 memory.
>>>>>> Adding changes to allocate memory from respective NUMA NODES of ITS devices.
>>>>>> This will optimize tables access and avoids unnecessary inter-node traffic."
>>>>> But more importantly, I'd like to see figures showing the actual benefit
>>>>> of this per-node allocation. Given that both of you guys have access to
>>>>> such platforms, please show me the numbers!
>>>> I'll share the actual results which shows the improvement whenever
>>>> available on our next chips. Current version of Qualcomm qdf2400 doesn't
>>>> support multi socket configuration to capture results and share with you.
>>>> Do you see any other issues with this patch apart from the performance
>>>> improvements. I strongly believe this brings the noticeable improvement
>>>> in numbers on systems where it has multi node memory/CPU configuration.
>>> I agree that it *could* show an improvement, but it very much depends on
>>> how often the ITS misses in its caches. For this kind of patches, I want
>>> to see two things:
>>> 1) It brings a measurable benefit on NUMA platforms
>> Did some measurement of interrupt response time for LPIs and we don't
>> see any major
>> improvement due to caching of Tables. However, we have seen
>> improvements of around 5%.
> An improvement of what exactly?

interrupt response time.
> M.
> --
> Jazz is not dead. It just smells funny...