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To: David Xu <davidxu@freebsd.org>
From: "Poul-Henning Kamp" <phk@phk.freebsd.dk>
In-Reply-To: Your message of "Thu, 27 Oct 2005 15:12:21 +0800."
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Date: Thu, 27 Oct 2005 10:20:20 +0200
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Cc: current@freebsd.org, Marian Hettwer <MH@kernel32.de>
Subject: Re: MySQL Performance 6.0rc1 
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In message <43607DD5.3020708@freebsd.org>, David Xu writes:

>Check gettimeofday syscall, it follows every I/O syscall, I think
>our gettimeofday is tooooooo expensive, if we can directly get time from
>memory, the performance will be improved further.

Why would anybody take a timestamp at all I/O syscalls ? 

"I wonder why my car can only go 30 km/h with the trunk full of concrete" ?

In a data base application I could possibly understand a timestamp
after every write.

But after _all_ I/O syscalls ?  That's just plain stupid...

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.