linux-kernel - Re: [RFC][PATCH 09/11] perf_counter: revamp syscall input ABI

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Date:	Thu, 19 Mar 2009 09:15:16 +1100
From:	Paul Mackerras <paulus@...ba.org>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	mingo@...e.hu, rostedt@...dmis.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH 09/11] perf_counter: revamp syscall input ABI

Peter Zijlstra writes:

> Ah, I thought we should keep a pure 64 bit raw value. You never know
> what hardware will do.

Oh I see, you use hw_event->raw_event if hw_event->raw is set.  I
missed that before.

Still, you're putting that into hwc->config along with other bits like
ARCH_PERFMON_EVENTSEL_USR and ARCH_PERFMON_EVENTSEL_OS, so I would
think we could spare two bits for the type, leaving 62 bits for the
raw event code.  And if that isn't enough, there's the
hw_event.extra_config_len field, which allows userspace to pass in
arbitrary amounts of extra PMU configuration data.

Paul.
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