Re: [Xen-devel] [PATCH] x86/apic/x2apic: Share IRQ vector between cluster members only when no cpumask is specified

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 08/08/2017 09:28 AM, Andrew Cooper wrote:
> On 08/08/17 14:25, Boris Ostrovsky wrote:
>> On 08/08/2017 05:48 AM, Jan Beulich wrote:
>>>>>> Andrew Cooper <andrew.cooper3@xxxxxxxxxx> 08/07/17 7:19 PM >>>
>>>> More than once, we've discussed freeing up the legacy PIC range of
>>>> vectors, and freeing up the unallocated vectors in 0xfx.
>>> And that's something I would prefer over the change proposed here,
>>> albeit I realize that the amount of vectors to recover isn't that large.
>> That would only net us 32 vectors at the most. That probably wouldn't be
>> sufficient in many cases where we are currently having vector shortage.
>> Unfortunately I don't have access to my failing system to say how may
>> vectors I was short but I believe it was more than that.
> Indeed, which is why I haven't actually undertaken the work.  It doesn't
> come close to solving the problem.
>
>> (I am also not sure I understand what is meant by "freeing". Where are
>> they going?)
> By "freeing", I mean "available for general irq use" rather than being
> reserved and unused in the system.
>


OK, so it's then definitely less than 32 vectors that would become
available.

I will send v2 of this patch.

-boris

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