linux-kernel - Re: [RFC][PATCH] perf: Add a few generic stalled-cycles events

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Date:	Mon, 15 Oct 2012 17:55:34 +0200
From:	Robert Richter <robert.richter@....com>
To:	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
CC:	<acme@...hat.com>, <mingo@...nel.org>, <peterz@...radead.org>,
	<eranian@...gle.com>, <asharma@...com>,
	Anton Blanchard <anton@....ibm.com>, <paulus@...ba.org>,
	<mpjohn@...ibm.com>, <linuxppc-dev@...abs.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCH] perf: Add a few generic stalled-cycles events

On 11.10.12 18:28:39, Sukadev Bhattiprolu wrote:
> +  { .type = PERF_TYPE_HARDWARE, .config = PERF_COUNT_HW_STALLED_CYCLES_FIXED_POINT },
> +  { .type = PERF_TYPE_HARDWARE, .config = PERF_COUNT_HW_STALLED_CYCLES_LOAD_STORE },
> +  { .type = PERF_TYPE_HARDWARE, .config = PERF_COUNT_HW_STALLED_CYCLES_INSTRUCTION_FETCH },
> +  { .type = PERF_TYPE_HARDWARE, .config = PERF_COUNT_HW_STALLED_CYCLES_BRANCH },

Instead of adding new hardware event types I would prefer to use raw
events in conjunction with sysfs, see e.g. the intel-uncore
implementation. Something like:

 $ find /sys/bus/event_source/devices/cpu/events/
 ...
 /sys/bus/event_source/devices/cpu/events/stalled-cycles-fixed-point
 /sys/bus/event_source/devices/cpu/events/stalled-cycles-load-store
 /sys/bus/event_source/devices/cpu/events/stalled-cycles-instruction-fetch
 /sys/bus/event_source/devices/cpu/events/stalled-cycles-branch
 ...
 $ cat /sys/bus/event_source/devices/cpu/events/stalled-cycles-fixed-point
 event=0xff,umask=0x00

Perf tool works then out-of-the-box with:

 $ perf record -e cpu/stalled-cycles-fixed-point/ ...

The event string can easily be reused by other architectures as a
quasi standard.

-Robert

-- 
Advanced Micro Devices, Inc.
Operating System Research Center

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