linux-kernel - Re: [PATCH] Performance Stats: Kernel patch

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Message-ID: <466507B4.2070802@linux.vnet.ibm.com>
Date:	Tue, 05 Jun 2007 12:20:28 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Maxim Uvarov <muvarov@...mvista.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Shailabh Nagar <nagar@...son.ibm.com>,
	Balbir Singh <balbir@...ibm.com>, Jay Lan <jlan@...r.sgi.com>
Subject: Re: [PATCH] Performance Stats: Kernel patch

Andrew Morton wrote:
> On Wed, 30 May 2007 18:49:46 +0000
> Maxim Uvarov <muvarov@...mvista.com> wrote:
> 
>> +void print_taskstats(struct taskstats *t)
>> +{
>> +	printf("\n\nTask   %15s%15s\n"
>> +	       "       %15lu%15lu\n",
>> +	       "voluntary", "nonvoluntary",
>> +	       t->nvcsw, t->nivcsw);
>> +}
> 
> print_task_stats versus print_taskstats is a bit confusing, but I guess it
> doesn't matter.
> 
> More significantly, the whole idea of calling it "task stats" isn't a good
> one: it's far too general.  The whole kernel interface is called taskstats,
> but the additions here are a tiny part of that.
> 
> Perhaps task_context_switch_rates would be more appropriate, although
> rather a lot to type.
>

I agree, taskstats is the name given to the genetlink interface.

 
> The patch otherwise seems OK.  Thoughts:
> 
> - Do we need to increment TASKSTATS_VERSION for this?  I forget the rules
>   there.

Any ABI change should result in a version bump. So the bump is ok

> 
> - The lack of context-switch accounting in taskstats is, I think, a
>   simple oversight.  It should have been included on day one.  
> 

Yes, it should have been included

>   There are perhaps other things which _should_ be in taskstats, but we
>   forgot to add them.  Can we think of any such things?
>

I think it's worth reviewing the data exported. I thought CSA filled
out the gaps, but it's definitely worth revisiting.

 
>   We shouldn't just toss any old random stuff in there: it should be
>   things which make sense, and which Unix or Linux accounting traditionally
>   provides, and it should be something which we expect won't suddenly
>   become unsupportable if people make internal kernel changes.
> 

Yes, agreed. The interface must also be open for changes to accounting information
that might be useful as a result of new features, like containers, etc.

-- 
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL
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