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Subject: Re: [RFT][patch 17/18] sched: use jump labels to reduce overhead
 when bandwidth control is inactive
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Richard Henderson <rth@redhat.com>
Cc: Jason Baron <jbaron@redhat.com>, Paul Turner <pjt@google.com>,
        linux-kernel@vger.kernel.org,
        Bharata B Rao <bharata@linux.vnet.ibm.com>,
        Dhaval Giani <dhaval.giani@gmail.com>,
        Balbir Singh <bsingharora@gmail.com>,
        Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>,
        Srivatsa Vaddagiri <vatsa@in.ibm.com>,
        Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>,
        Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>,
        Ingo Molnar <mingo@elte.hu>, Pavel Emelyanov <xemul@openvz.org>
Date: Fri, 05 Aug 2011 17:14:14 +0200
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On Fri, 2011-08-05 at 08:11 -0700, Richard Henderson wrote:
> On 08/05/2011 01:30 AM, Peter Zijlstra wrote:
> > OK, so _WHY_ does that make a difference and will a next version of
> > gnu-binutils not mess that up?
> 
> The Why is micro-architectual, and I can't answer that.
> 
> But ld will never re-order the files as given on the command-line.
> There are too many functions and tables that are constructed 
> piece-wise from input sections; re-ordering them would change
> the semantics of the program.

Right, so I was wondering about things like whole-program-optimization
passes at link time. Since I've no clue why the proposed patch does what
it does, its hard to say what invariant is needed to be kept.