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Message-ID: <1317938915.4729.31.camel@gandalf.stny.rr.com>
Date: Thu, 06 Oct 2011 18:08:34 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Jeremy Fitzhardinge <jeremy@...p.org>
Cc: "H. Peter Anvin" <hpa@...or.com>, Jason Baron <jbaron@...hat.com>,
"David S. Miller" <davem@...emloft.net>,
David Daney <david.daney@...ium.com>,
Michael Ellerman <michael@...erman.id.au>,
Jan Glauber <jang@...ux.vnet.ibm.com>,
the arch/x86 maintainers <x86@...nel.org>,
Xen Devel <xen-devel@...ts.xensource.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>,
peterz@...radead.org, rth@...hat.com
Subject: Re: [PATCH RFC V2 3/5] jump_label: if a key has already been
initialized, don't nop it out
On Thu, 2011-10-06 at 14:39 -0700, Jeremy Fitzhardinge wrote:
> I'm not sure it would be a win, necessarily. My test with back-to-back
> jmp2 was definitely slower than with the nop padding it out to 5 bytes;
> I suspect that's a result of having too many jmps within one cacheline.
> Of course, there's no reason why the CPU would optimise for jumps to
> jumps, so perhaps its just hitting a "stupid programmer" path.
Just a note. Micro-benchmarks are known to be as good as political polls
and statistics. They show a much different view of the world than what
is really there.
-- Steve
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