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Date: Tue, 25 Feb 2014 16:11:00 -0000
From: =?utf-8?B?T25kxZllaiBCw61sa2E=?= <neleai@seznam.cz>
To: bugdal at aerifal dot cx <sourceware-bugzilla@sourceware.org>
Cc: glibc-bugs@sourceware.org
Subject: Re: [Bug nptl/16630] Use SYSENTER for pthread_cond_broadcast/signal() (i.e. fix "FIXME: Ingo" issue)
Message-ID: <20140225161112.GA21809@domone.podge>
References: <bug-16630-131@http.sourceware.org/bugzilla/> <bug-16630-131-tWjO7oaks6@http.sourceware.org/bugzilla/>
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On Tue, Feb 25, 2014 at 05:47:16AM +0000, bugdal at aerifal dot cx wrote:
> http://sourceware.org/bugzilla/show_bug.cgi?id=16630
> 
> --- Comment #3 from Rich Felker <bugdal at aerifal dot cx> ---
> On Tue, Feb 25, 2014 at 04:51:18AM +0000, cjones.bugs at gmail dot com wrote:
> > Do you happen to know if that's filed already?  I'm curious what it would be
> > replaced with.
> 
> There is portable C code for all of these functions already and a
> strong sentiment from some users and developers that the asm is
> unnecessary, error-prone, and lags behind the C in getting fixes and
> improvements. See the related thread on the libc-alpha mailing list:
> 
> [RFC][BZ #16549, #16410] Remove pthread_(cond)wait assembly implementations?
> 
> Basically I think if it could be demonstrated that the C performs just
> as well (or within a margin of difference that's not significant), the
> asm could be removed.
> 
Actually c is around 5000 cycles faster. My guess is that its because
assembly does extra syscall which has bigger impact than
microoptimizations, I did not trace that yet.