linux-kernel - Re: [patch] perf_events: even more wrong events for AMD fam10h

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Date:	Mon, 27 Jun 2011 13:22:21 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Vince Weaver <vweaver1@...s.utk.edu>
Cc:	linux-kernel@...r.kernel.org, Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...e.hu>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Robert Richter <robert.richter@....com>,
	Stephane Eranian <eranian@...gle.com>,
	Andre Przywara <andre.przywara@....com>
Subject: Re: [patch] perf_events: even more wrong events for AMD fam10h

On Tue, 2011-06-07 at 17:07 -0400, Vince Weaver wrote:
> Here are two more problems I found with the superlative "generalized" 
> events on AMD fam10h.
> 
> The "l1-dcache-loads" event measures loads *and* stores.
>     This might be as close as you can get on AMD, but it's still wrong
>       as it's not what Intel measures.  
>     My patch removes it.  Better might be to add a proper
>     "l1-dcache-access" event.

The question to ask is, does it still have a strong correlation?

> The "l1-dcache-load-miss" event is an invalid event. (0x141).
>     From what I can tell that event (DATA_CACHE_MISSES) does not
>     take a mask.  It should be 0x41.  And it's actually measuring
>     all misses, not just load misses, see above.

See commit 83112e688f5f05dea1e63787db9a6c16b2887a1d. Also same as above.

> The "l1-dcache-stores" event does not work.  See the
>      ./validation/l1-dcache-stores test found in 
>      http://web.eecs.utk.edu/~vweaver1/projects/perf-events/validation.html
>    So remove it until we figure out why.
> 

Robert?

> Also, is the value for "no such event" 0 or -1?  The perf_event_amd.c
> file seems to use them interchangably from what I can tell.

	val = hw_cache_event_ids[cache_type][cache_op][cache_result];

	if (val == 0)
		return -ENOENT;

	if (val == -1)
		return -EINVAL;


But yeah, somewhat inconsistent. Robert, Andre, could you guys go over
the AMD events some time?
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