linux-kernel - Re: [PATCH 0/4] RFC: jump label

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Message-Id: <20090903211142.8490C47C94@magilla.sf.frob.com>
Date:	Thu,  3 Sep 2009 14:11:42 -0700 (PDT)
From:	Roland McGrath <roland@...hat.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Jason Baron <jbaron@...hat.com>, linux-kernel@...r.kernel.org,
	mathieu.desnoyers@...ymtl.ca, rth@...hat.com
Subject: Re: [PATCH 0/4] RFC: jump label - (tracepoint optimizations)

> This looks really interesting and desired. Once GCC adds this (or an 
> equivalent) feature, i'd love to have your optimization in the 
> kernel.

We expect it will be in gcc 4.5 and backported to Fedora's 4.4 pretty soon.
But it's not finalized yet, so we are only doing proof-of-concept so far.

> Basically everything that is optional and touches some very hot 
> codepath would be eligible - not just tracepoints.

Sure.  Any place you have a load+conditional-jump where that is too costly,
we can make it a nop that costs a only cycle or so.  We probably want to
think a little harder about the nicest macro setup we can do to make
employing this trivial in the source.

Thanks,
Roland
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