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From: Ross Johnson <Ross.Johnson@homemail.com.au>
To: Ramiro Polla <ramiro@lisha.ufsc.br>,
	  Pthreads-Win32 list <pthreads-win32@sourceware.org>
Subject: Re: Static libraries initialization
Date: Sat, 26 Apr 2008 00:07:00 -0000	[thread overview]
Message-ID: <48127206.9060205@homemail.com.au> (raw)
In-Reply-To: <4811657E.40608@homemail.com.au>

Ross Johnson wrote:
>>
>> The overhead of one if()? If the branch prediction sets the if() to 
>> be unlikely, there should be 1 memory access and 1 cmp function 
>> overhead. It shouldn't even disturb the instruction pipeline.
> Yes, it's almost negligible and I use the same method to initialise 
> static POSIX mutexes, cond vars, etc., although this one is slightly 
> worse in that the data isn't necessarily in cache already or local. 
> IIRC, we need to use an Interlocked routine to compare the value, not 
> for atomicity necessarily but so that we get the memory barrier 
> effects right. And I've found that these calls can be relatively slow 
> due to bus locking. I'm also still assuming that every single routine 
> needs this overhead, but that may not be necessary in the end.
I'll retract my interlocked/memory fence comments - they aren't needed 
here. I keep forgetting it's just the first quick check, and the second 
thorough check will only ever be performed once or twice.

Ross

  reply	other threads:[~2008-04-26  0:07 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-04-24 12:53 Ramiro Polla
     [not found] ` <4810ABB9.10106@homemail.com.au>
     [not found]   ` <4810D5C3.2070306@lisha.ufsc.br>
2008-04-25  5:01     ` Ross Johnson
2008-04-26  0:07       ` Ross Johnson [this message]
2008-05-19 11:29       ` Roland Schwarz

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