linux-kernel - Re: [PATCH 3/7] x86/intel_rdt: Add support for cache bit mask management

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Date:	Wed, 20 May 2015 10:22:21 -0700 (PDT)
From:	Vikas Shivappa <vikas.shivappa@...el.com>
To:	Thomas Gleixner <tglx@...utronix.de>
cc:	Vikas Shivappa <vikas.shivappa@...el.com>,
	Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
	x86@...nel.org, linux-kernel@...r.kernel.org, hpa@...or.com,
	mingo@...nel.org, tj@...nel.org, peterz@...radead.org,
	Matt Fleming <matt.fleming@...el.com>,
	"Auld, Will" <will.auld@...el.com>, peter.zijlstra@...el.com,
	h.peter.anvin@...el.com,
	"Juvva, Kanaka D" <kanaka.d.juvva@...el.com>, mtosatti@...hat.com
Subject: Re: [PATCH 3/7] x86/intel_rdt: Add support for cache bit mask
 management



On Mon, 18 May 2015, Thomas Gleixner wrote:

> On Mon, 18 May 2015, Vikas Shivappa wrote:
>> On Fri, 15 May 2015, Thomas Gleixner wrote:
>>>> +static inline bool intel_rdt_update_cpumask(int cpu)
>>>> +{
>>>> +	}
>>>
>>> You must be kidding.
>>
>> the rapl and cqm use similar code. You want me to keep a seperate package mask
>> for this code which not would be that frequent at all ?
>
> You find for everything a place where you copied your stuff from
> without thinking about it, right?
>
> Other people dessperately try to fix the cpu online times which are
> more and more interesting the larger the systems become. So it might
> be a good idea to come up with a proper fast implementation which can
> be used everywhere instead of blindly copying code.

Ok , i can try to do this as a seperate patch after the cache allocation to get 
a support for faster implementation for traversing package and cpus in the 
packages which can be used by everyone. we would need to start from scratch with 
having packagemask_t equivalent to cpumask_t. hope that is fair ?

Thanks,
Vikas

>
>> for c-state transitions only idle_notifier gets called - so this is only when
>> a new package is physically added. and we dont need anything for cache alloc
>> for idle transitions. not really frequent ?
>
> Crap. It's called for every cpu which comes online and goes offline,
> not for new packages.
>
> Thanks,
>
> 	tglx
>
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