From owner-freebsd-hackers  Thu Dec 23 16: 7:55 1999
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Date: Thu, 23 Dec 1999 19:07:51 -0500
From: scott <scott@chronis.pobox.com>
To: Scott Hess <scott@avantgo.com>
Cc: freebsd-hackers@freebsd.org
Subject: Re: Status of kernel threads.
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I've found

http://www.cornfed.com/pk

looks weird, but says it will do kernel threads for FreeBSD.  It
replaces the kernel, though, so I don't know how it works with FreeBSD
hardware drivers.

I was bit by soddy mysql performance when the number of concurrent
clients and queries was high under FreeBSD, and have been looking into
solutions myself.

scott

On Thu, Dec 23, 1999 at 03:54:56PM -0800, Scott Hess wrote:
> I've been looking at hardware upgrades for a production MYSQL server.
> While banging on a hardware RAID solution, I found that the performance
> improvement for test harnesses hitting MYSQL sucked badly compared to other
> tests.  My hunch is that the blocking nature of disk I/O is interacting
> with FreeBSD's userland pthreads to effectively serialize disk requests
> (since disk I/O always blocks, there will never be multiple reads from disk
> in progress at a time, so no elevator sorting).  To verify the hunch, I ran
> multiple MYSQL daemons against the same database (using filesystem locking
> to synchronize), and hit each of them with 1/N of the load from the earlier
> test.  Indeed, the N-daemon version ran much faster overall, and showed
> much greater iostat numbers.
> 
> Does my evaluation of the problem make sense?  [For reference, in the
> 2-mysqld case, I ran 2 mysqld processes against a single set of tables on
> different ports, and hit each port with 2 100-unit client loads apiece, and
> 1-unit loads finished about 25% faster, while iostat tps numbers were about
> 40% higher.  With 4 mysqld processes and 1 100-unit client load apiece,
> units finished an additional 10% faster and iostat tps went up another 30%.
> All against a 32M cache SCSI-SCSI RAID5 controller with 6 10krpm drives.]
> 
> I periodically hear reference to kernel threads - but from what I can tell
> from following these lists for a couple months, and also searching the
> archives, kernel threads aren't quite "there" yet ("there"=="can
> use -kthread instead of -pthread and away we go").  Am I just missing the
> right search phrases?
> 
> Assuming the "kernel threads" still means "LinuxThreads" and not something
> new that I haven't found, does anyone have any positive or negative
> comments on how reasonable LinuxThreads on FreeBSD is for production use?
> Is it stable, or still in development?
> 
> Thanks,
> scott
> 
> 
> 
> 
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