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

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Date:   Mon, 10 Jul 2017 14:38:40 +0530
From:   Ganapatrao Kulkarni <gpkulkarni@...il.com>
To:     Marc Zyngier <marc.zyngier@....com>
Cc:     Shanker Donthineni <shankerd@...eaurora.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Vikram Sethi <vikrams@...eaurora.org>,
        Jayachandran C <jnair@...iumnetworks.com>,
        "ganapatrao.kulkarni@...ium.com" <ganapatrao.kulkarni@...ium.com>
Subject: Re: [PATCH] irqchip: gicv3-its: Use NUMA aware memory allocation for
 ITS tables

On Mon, Jul 10, 2017 at 2:36 PM, Marc Zyngier <marc.zyngier@....com> 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@....com> 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@...il.com> wrote:
>>>>>>> Hi Shanker,
>>>>>>>
>>>>>>> On Sun, Jun 25, 2017 at 9:16 PM, Shanker Donthineni
>>>>>>> <shankerd@...eaurora.org> 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...

thanks
Ganapat