linux-kernel - Re: [PATCH 1/1] perf tools: Add missing user space support for config1/config2

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Date:	Fri, 29 Apr 2011 21:32:37 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Vince Weaver <vweaver1@...s.utk.edu>
Cc:	Arnaldo Carvalho de Melo <acme@...radead.org>,
	linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Stephane Eranian <eranian@...il.com>,
	Lin Ming <ming.m.lin@...el.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 1/1] perf tools: Add missing user space support for
 config1/config2

* Vince Weaver <vweaver1@...s.utk.edu> wrote:

> On Wed, 27 Apr 2011, Ingo Molnar wrote:
> 
> > Secondly, you are still quite wrong even with your revised opinion. Being able 
> > to type '-e cycles' and '-e instructions' in perf and get ... cycles and 
> > instructions counts/events, and the kernel helping that kind of approach is not 
> > 'abstraction to the extreme', it's called 'common sense'.
> 
> by your logic I should be able to delete a file by saying
>
>   echo "delete /tmp/tempfile" > /dev/sdc1

> because using unlink() is too low of an abstraction and confusing to the 
> user.

Erm, unlink() does not pass magic hexa constants to the disk controller.

unlink() is a high level interface that works across a vast range of disk 
controllers, disks, network mounted filesystems, in-RAM filesystems, in-ROM 
filesystems, clustered filesystems and other mediums.

Just like that we can tell perf to count 'cycles', 'branches' or 
'branch-misses' - all of these are relatively high level concepts (in the scope 
of CPUs) that work across a vast range of CPU types and models.

Similarly, for offcore we want to introduce the concept of 'node local' versus 
'remote' memory - perhaps with some events for inter-CPU traffic as well - 
because that probably covers most of the NUMA related memory profiling needs.

Raw events are to perf what ioctls are to the VFS: small details nobody felt 
worth generalizing. My point in this discussion is that we do not offer new 
filesystems that support *only* ioctl calls ... Is this simple concept so hard 
to understand?

Thanks,

	Ingo
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