linux-kernel - Re: [PATCH 3/8] x86/intel_rdt/mba: Improvements to handle more RDT resources like MBA

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Message-ID: <alpine.DEB.2.10.1701171652370.15892@vshiva-Udesk>
Date:   Tue, 17 Jan 2017 16:53:23 -0800 (PST)
From:   Shivappa Vikas <vikas.shivappa@...el.com>
To:     Thomas Gleixner <tglx@...utronix.de>
cc:     Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
        vikas.shivappa@...el.com, linux-kernel@...r.kernel.org,
        x86@...nel.org, hpa@...or.com, mingo@...nel.org,
        peterz@...radead.org, ravi.v.shankar@...el.com,
        tony.luck@...el.com, fenghua.yu@...el.com, h.peter.anvin@...el.com
Subject: Re: [PATCH 3/8] x86/intel_rdt/mba: Improvements to handle more RDT
 resources like MBA



On Mon, 16 Jan 2017, Thomas Gleixner wrote:

> On Tue, 10 Jan 2017, Vikas Shivappa wrote:
>> This patch does some changes to get ready to handle more resources like
>> Memory b/w allocation(MBA).
>>
>> -Update the control registers only when user changes the controls(cbm for
>> Cache resources and Mem b/w for memory). Hence not sending IPIs on all
>> domains when user updates the control vals.
>> -Introduce next_enabled_resource rather than looping through all
>> resources while parsing each schemata line. The order of resources
>> should be anyways the same as the root schemata.
>> -Return error as soon as we detect a resource not entering all domain
>> values in schemata rather than waiting till we parse all resources.
>
> That looks all like reasonable optimizations and I have a hard time to
> understand why this is a prerequisite for the bandwidth support.
>
> And each of these changes is independent so they should be in seperate
> patches.

Ok will split them. Its not a pre requisite for MBA. Should i send as a seperate 
series ?

>
>> +/*
>> + * Parameter r must be NULL or pointing to
>> + * a valid rdt_resource_all entry.
>> + * Points r to the next enabled RDT resource at the end.
>> + */
>> +#define next_enabled_rdt_resource(r)					\
>> +do {									\
>> +	if (!r)								\
>> +		r = rdt_resources_all;					\
>> +	else								\
>> +		r++;							\
>> +	for (; r < rdt_resources_all + RDT_NUM_RESOURCES; r++)		\
>> +		if (r->enabled)						\
>> +			break;						\
>> +} while (0)
>
>
> This is crap, really. What the heck is wrong with a proper function?
>
> static struct rdt_resource *get_next_enabled_resource(struct rdt_resource *r)
> {
> 	....
>
> 	return r;
> }
>

Will fix,

Thanks,
Vikas

> Thanks,
>
> 	tglx
>