linux-kernel - Re: [patch 1/2] x86, x2apic: minimize IPI register writes using cluster groups v4

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Date:	Tue, 03 May 2011 10:59:45 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Suresh Siddha <suresh.b.siddha@...el.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [patch 1/2] x86, x2apic: minimize IPI register writes using cluster
 groups v4

On 05/03/2011 10:31 AM, Ingo Molnar wrote:
> 
> * Cyrill Gorcunov <gorcunov@...il.com> wrote:
> 
>> On 05/02/2011 07:05 PM, Ingo Molnar wrote:
>> ...
>>>>
>>>>   Ingo, would it be fine to make apic->init() either _before_ this series or 
>>>> on top of them (because if I introduce it inside this particular patch it 
>>>> would contain some unrelated code snippets such as .init = NULL for all apics 
>>>> declaration).
>>>
>>> Of course it should be a separate patch - even this patch looks a bit large - 
>>> any way to split it up further?
>>
>>   Well, for this particular path the only minimum is used, so i fear there is no
>> way to split it, probably I could drop some 'cleanup' bits from it and make it
>> a separate one. Gimme some time.
> 
> Well, first try to do *all* preparatory and cleanup changes that have low 
> regression risk.

OK

> 
> *Then* keep the most dangerous part to the end of it - so that it's easily 
> reverted, should the need arise. Preferably the dangerous part should be much 
> smaller than:
> 
>  3 files changed, 136 insertions(+), 46 deletions(-)
> 
> And no, it is not at all true that there is 'no way' to split the patch up any 
> further: you could certainly add the data structures, init methods and such 
> support code (which is low regression risk) in a separate patch than the 
> changes that modify the existing x2apic_send_IPI_mask_allbutself() function and 
> such.

OK

> 
> Also, the loop body in the new __x2apic_send_IPI_mask() function could 
> certainly be split out into a helper inline, making the code flow clearer.

OK, will try so, thanks Ingo!

> 
> Thanks,
> 
> 	Ingo


-- 
Thanks,
  Cyrill
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