Date: Thu, 26 Mar 1998 14:59:56 +1030 From: Greg Lehey <grog@lemis.com> To: "Daniel R. Brownstone" <drbrowns@ls.wustl.edu> Cc: questions@FreeBSD.ORG Subject: Re: Optimizing FreeBSD Message-ID: <19980326145956.12247@freebie.lemis.com> In-Reply-To: <Pine.BSF.3.96.980325200608.8638E-100000@ls.wustl.edu>; from Daniel R. Brownstone on Wed, Mar 25, 1998 at 08:09:27PM -0600 References: <19980326122209.64374@freebie.lemis.com> <Pine.BSF.3.96.980325200608.8638E-100000@ls.wustl.edu>
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On Wed, 25 March 1998 at 20:09:27 -0600, Daniel R. Brownstone wrote:
> On Thu, 26 Mar 1998, Greg Lehey wrote:
>
>> FreeBSD adapts to the user load much better than earlier versions of
>> UNIX did, so there's not much call for the kind of optimization that I
>> suspect you're talking about. In general, unless you have performance
>> problems, you don't need to do much. If you do have problems, you
>> need to address them individually. On this list, this means you need
>> to tell us what the problems are.
>
> Funny you should mention that.
>
> We have up to about 30 users logged on simulatenously, some via modem (up
> to 56k), and the rest via 100 Base T. Recently (the last couple of
> months) at various times -- usually during heavy usage -- the system will
> slow down very quickly, and finally just freeze up, with the only solution
> being to do a hard reboot. Very annoying. I can't find any processes
> that are always running at the time, and with my lack of sophistication, I
> can't otherwise diagnose the error. When this all started, we were
> running 2.2-SNAP from like October 96, and so I upgraded to 2.2.5-STABLE.
> However, the problem has not corrected itself.
Hmmm. I wouldn't consider this a matter for tuning. I'd call it a
bug.
> One thing of interest is that when the system does lock up, the "IN USE"
> light on one of the hard drives is always on solid. Near as I can tell,
> however, it's not always the same drive.
>
> The system is a Proliant 5000 with 256 MB of RAM and a few GB of storage.
>
> Does that help?
It brings us a lot closer. Let's consider what it could be:
1. You mention a disk light being on. This could be a clue, but I've
noticed that happening a number of times when disk access wasn't
the problem, so we should defer that until we have to look at it.
2. You have a 100 BaseT network. What kind of board? Could be that
there are problems with the driver. Could be that they're coupled
with problems with the net (bad cable, for example).
3. You say the system slows down over a period of time. Is this the
case from the console as well? Maybe you can recognize some kind
of unusual circumstance, like excessive retransmits or such. I
can't tell you where to look here, just how to go about looking
for it.
4. You should consider building a debug kernel with the kernel
debugger. You can strip the kernel before booting, but you need
the debug version (about 10 MB) for dump analysis. Take a look at
the online handbook for more details. That way we at least have
an idea of what has gone wrong.
Greg
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