linux-kernel - Re: [tip:perf/core] perf/x86/intel: Clean-up/reduce PEBS code

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Message-ID: <20130916160311.GW18242@two.firstfloor.org>
Date:	Mon, 16 Sep 2013 18:03:11 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Andi Kleen <andi@...stfloor.org>, mingo@...nel.org, hpa@...or.com,
	linux-kernel@...r.kernel.org, tglx@...utronix.de,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:perf/core] perf/x86/intel: Clean-up/reduce PEBS code

> There already was an implicit division there, and
> sizeof(pebs_record_hsw) = 176, can it really optimize that constant
> division?

Yes it can (if nothing else then by converting it to * 1/x)

The only exception is with -Os, but if you want performance
you should not be using that anyways.

You could do that manually, but it's easiest to just keep
the code paths separate and let the compiler worry about it.

> I suppose we could go and introduce CONFIG_PERF_DEBUG and stuff sanity
> checks under that.. :/

Hmm, it's not a sanity check?

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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