Subject: Re: [GIT pull] irq updates for 4.13
To: Thomas Gleixner <tglx@linutronix.de>,
        Linus Torvalds <torvalds@linux-foundation.org>
References: <alpine.DEB.2.20.1707030923220.2188@nanos>
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 <alpine.DEB.2.20.1707042108120.2131@nanos>
 <1d9fe4ab-72a2-dc86-8beb-39c586a04545@mellanox.com>
CC: Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>,
        LKML <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Ingo Molnar <mingo@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>
From: Max Gurtovoy <maxg@mellanox.com>
Message-ID: <904c392a-5e3c-3f2b-5ae9-6326d8fef265@mellanox.com>
Date: Thu, 6 Jul 2017 16:58:39 +0300
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On 7/4/2017 11:48 PM, Max Gurtovoy wrote:
>
>
> On 7/4/2017 10:10 PM, Thomas Gleixner wrote:
>> On Tue, 4 Jul 2017, Linus Torvalds wrote:
>>> On Tue, Jul 4, 2017 at 8:17 AM, Jens Axboe <axboe@kernel.dk> wrote:
>>>> On 07/03/2017 06:00 PM, Linus Torvalds wrote:
>>>>>
>>>>> If they ever do come online, does that get fixed? I don't know.
>>>>> Somebody should check.
>>>>
>>>> Yes, the blk-mq cpu hotplug code updates mappings when CPUs come and
>>>> go, so that part is fine. That's exercised everytime the laptop is
>>>> suspended and resumed.
>>>
>>> I don't think that's true any more. Commit fe631457ff3e changed it to
>>> map the initial CPU's sequentially whether they are online or not.
>>> Only after you run out of hardware queues will we start playing games.
>>>
>>> That's what worries me about the conflict - the two changes did very
>>> different things to the same code. I'd really like somebody to take a
>>> look at my resolution, and just in general how those two different
>>> changes work together.
>>
>> Hmm, I leave that to Christoph. He wrote the irq stuff and reviewed
>> fe631457ff3e.
>>
>> Thanks,
>>
>>     tglx
>>
>
> Hi Linus,
> From code reviewing the changes you made during the merge, I'm good with
> my commit purpose (fix the mapping between CPUs and HWQs). You actually
> replaced the "struct cpumask *online_mask" with cpu_online(cpu) function
> and it's fine. I'll run some tests to see that I'm not missing something.
> Regarding the second patch from Christoph, let's wait for his review (I
> can also test other scenarios like offline/online CPU's after initial
> mapping of CPUs to HWQs).
>
> Cheers,
> Max.

FYI,
My tests for the mapping between (72) CPUs and (64) HWQs passed 
successfully with 4.12.0+.