Date: Fri, 12 Jul 2002 18:20:17 -0700 (PDT) From: Matthew Dillon <dillon@apollo.backplane.com> To: "Ken Menzel" <kenm@icarz.com> Cc: "Hartmann, O." <ohartman@klima.physik.uni-mainz.de>, <freebsd-stable@FreeBSD.ORG> Subject: Re: tuning(7) request was: Re: Performance boost with kernel options in FBSD 4.6 Message-ID: <200207130120.g6D1KHoq064689@apollo.backplane.com> References: <20020710104730.L10343-100000@klima.physik.uni-mainz.de> <04a601c228dc$c6dbb980$681663cf@icarz.com> <200207111930.g6BJUX5m096974@apollo.backplane.com> <064901c22919$9738d2c0$681663cf@icarz.com>
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:Hi Matt,
: Regarding your comment about highly IO intensive programs; many of
:us run SQL databases (highly intensive IO). I have noticed a tendency
:for a single process to monopolize the CPU with MySQL, to the
:exclusion of other users. I do understand the detrimental effects of
:state changes on a CPU, so I can relate to not setting this value too
:high. I wonder if we might see an effect with this as well?
:
:I don't remember seeing this discussed here. I do not mean to bring
:up a topic that has been discussed before, either here or another
:list. However, the effect on IO for a server with several hundred
:simultaneous connections could be noticeable. I am not sure a simple
:benchmark would should any advantage, although I am planning to play
:...
:
:The main thing I was wondering is what effects I might watch for, and
:any hints as to what I should not waste my time on. In our
:environment we run FreeBSD,Apache,PHP, MySQL for about a thousand
:users. It is an interactive database application so this may have
:...
:Thanks for the input,
:Ken
Well, this is a bit too vague for me to give a specific answer.
In general terms if you are running a mix of services the two
big issues are going to be (1) memory, and (2) multiple disks.
You can observe disk loads using 'systat -vm 1', and you can observe
memory from the same command. Disk loads are in the lower left
corner (look at the percentage load, not the transfer rates),
and VM is displayed on the right, where programs 'eat' free memory
and pages are shift downward, from active to inactive to cache to
free. But for VM the the 'react'ivation rate on the right can be an
indicator that the system is starting to overload. Reactivation
rates beyond a few hundred pages per second would be an indication
that more investigation is required.
-Matt
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