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Date: Fri, 28 Oct 2005 21:25:03 +0800
From: David Xu <davidxu@freebsd.org>
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Cc: Pertti Kosunen <pertti.kosunen@pp.nic.fi>,
	Poul-Henning Kamp <phk@phk.freebsd.dk>, current@freebsd.org,
	"Yuriy N. Shkandybin" <jura@networks.ru>
Subject: Re: Timers and timing, was: MySQL Performance 6.0rc1
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Bernd Walter wrote:

>On Fri, Oct 28, 2005 at 06:43:10PM +0800, David Xu wrote:
>  
>
>>Poul-Henning Kamp wrote:
>>    
>>
>>>In message <4361FDBE.7000500@freebsd.org>, David Xu writes:
>>>
>>>
>>>the correct way to optimize this would be to add a time(2) systemcall
>>>which returns the value of the kernel global time_second.
>>>
>>>      
>>>
>>Can we make a page in kernel address space which is readable my user
>>code? put the variable in the page, I know read an integer is atomic-op,
>>needn't lock, so syscall is not needed.
>>    
>>
>
>Don't whink it is importent for 1s intervalls, but atomic != coherent.
>
>  
>
That's just an idea. :-)
As robert said, add a lower resolution CLOCK_ type  may work well.
Another thing I just though of, if reading timercounter is so slow, won't
gettimeofday hardly block cpu too many cycles ? the cpu is just stucked
there by a slow clock in hardware signals.