Re: [PATCH 3/4, v2] x86: enlightenment for ticket spin locks - eliminateNOPs introduced by first patch

From: H. Peter Anvin
Date: Wed Jun 30 2010 - 13:13:41 EST

On 06/30/2010 12:07 AM, Jan Beulich wrote:
>> If you're stretching (bloating) them anyway, perhaps we should be using
>> "add" instructions instead, with their better EFLAGS behavior?
> Hmm, yes, that possibility I didn't even consider. Would have
> the potential to get away without that admittedly ugly "unary"
> assembler macro altogether, though at the price of growing all
> instructions rather than just those that have a non-symbolic
> and small displacement. Since unlock generally gets inlined, I'm
> not certain this additional growth in code size would be
> acceptable...
> Please let me know, though before submitting an eventual third
> version I'd appreciate knowing especially the first two patches
> need further changes in order to get accepted.

Will look at it today, hopefully. The Syslinux 4.00 release has
unfortunately occupied me over the last week-plus.

As far as the "unary" macro is concerned... I have to admit I couldn't
even figure out what it was supposed to do. It could definitely use a
better comment.


H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.

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