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Date:      Sun, 10 Dec 2000 11:29:21 -0500
From:      mbac@mmap.nyct.net (Michael Bacarella)
To:        David Schwartz <davids@webmaster.com>
Cc:        Noor Dawod <noor@comrax.com>, stable@FreeBSD.ORG
Subject:   Re: MySQLd not using both CPUs
Message-ID:  <20001210112921.A5531@mmap.nyct.net>
In-Reply-To: <NCBBLIEPOCNJOAEKBEAKOEADMGAA.davids@webmaster.com>; from davids@webmaster.com on Sun, Dec 10, 2000 at 12:54:01AM -0800
References:  <PHEBIOJOBJJLIIJCOINKEEDHCPAA.noor@comrax.com> <NCBBLIEPOCNJOAEKBEAKOEADMGAA.davids@webmaster.com>

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On Sun, Dec 10, 2000 at 12:54:01AM -0800, David Schwartz wrote:

> 	2) Multiple I/O operations can be pending. The whole process won't be stuck
> waiting a file to be read.

In my experience, that doesn't happen. What does instead happen is that
an operation that would block is instead delayed and sched_yield() is
called.

In cases where nothing can be done (waiting for 10 read()s to complete and
all would block, for example), you go into a busy wait loop.

> 	However, there is at least one caveat -- each thread will show as a process
> in tools like 'ps', which can be disconcerting. You may also need to raise
> the limit on the number of processes you can have, because to the kernel,
> each thread is a process.

>       My recollection is that MySQLd works perfectly with LinuxThreads on Linu
> There should be no reason it should be any different on FreeBSD. The trick
> will be getting the configuration right. Be sure to read the
> 'README.FreeBSD' file included with the LinuxThreads port.

I think the whole 1 thread to 1 process scheme that LinuxThreads uses would
be much slower under FreeBSD. Unless some magic has been put in
to special case this scheme in the scheduler... you'll probably see
better performance running LinuxThreads with Linux.

-- 
Michael Bacarella <mbac@mmap.nyct.net>	;finger address for public key
GPG Key Fingerprint: B4E4 82F5 BCAC AB83 E6F7  B5AA 933E 2A75 79A4 A9C1
Technical Staff / New York Connect Net


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