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>
 <CA+55aFxPE5St5S1_C7AC-d+=Q7_cQcPmjmP=rdHBp8e4f9ZRqw@mail.gmail.com>
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 <alpine.DEB.2.20.1707042108120.2131@nanos>
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: <1d9fe4ab-72a2-dc86-8beb-39c586a04545@mellanox.com>
Date: Tue, 4 Jul 2017 23:48:17 +0300
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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.