linux-kernel - Re: [patch] Performance Counters for Linux, v3

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Date:	Thu, 11 Dec 2008 11:11:00 -0800
From:	"Tony Luck" <tony.luck@...el.com>
To:	"Ingo Molnar" <mingo@...e.hu>
Cc:	linux-kernel@...r.kernel.org,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Stephane Eranian" <eranian@...glemail.com>,
	"Eric Dumazet" <dada1@...mosbay.com>,
	"Robert Richter" <robert.richter@....com>,
	"Arjan van de Veen" <arjan@...radead.org>,
	"Peter Anvin" <hpa@...or.com>,
	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>,
	"Paul Mackerras" <paulus@...ba.org>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [patch] Performance Counters for Linux, v3

>        /*
>         * Special "software" counters provided by the kernel, even if
>         * the hardware does not support performance counters. These
>         * counters measure various physical and sw events of the
>         * kernel (and allow the profiling of them as well):
>         */
>        PERF_COUNT_CPU_CLOCK            = -1,
>        PERF_COUNT_TASK_CLOCK           = -2,
>        /*
>         * Future software events:
>         */
>        /* PERF_COUNT_PAGE_FAULTS       = -3,
>           PERF_COUNT_CONTEXT_SWITCHES  = -4, */

  ...
> +[ Note: more hw_event_types are supported as well, but they are CPU
> +  specific and are enumerated via /sys on a per CPU basis. Raw hw event
> +  types can be passed in as negative numbers. For example, to count
> +  "External bus cycles while bus lock signal asserted" events on Intel
> +  Core CPUs, pass in a -0x4064 event type value. ]

It looks like you have an overlap here.  You are using some negative numbers
to denote your special software events, but also as "raw" hardware events.
What if these conflict?

-Tony
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