Re: FC3 and system performance

From: prg (rdgentry1_at_cablelynx.com)
Date: 12/21/04 

Date: 21 Dec 2004 09:13:13 -0800

Ross wrote:
> Hi,
> we have a biprocessor server (PIII 500 Mhz, 256 Mb RAM) running
Fedora
> Core 3 with severe perfomance problems. Memory usage is almost at
99%,
> the swap partition has ben set to 2 Gb but it is never used.
> The cached memory is now more than 170 Mb.
>
> This is the output of FREE:
>
> total used free shared buffers
>
> Mem: 254980 252984 1996 0 17620
> cached
> 172984
>
> -/+ buffers/cache: 62380 192600
>
> Swap: 2100816 15520 2085296
>
>
> The system is slow and network users (roughly 15) complain about
that.
> Why the swap partition is not being used? We could add more RAM but,
> in general, how can we optimize the system performance?
>
> Thanks.

You don't mention anything about the nature of use, but must assume you
have some network app that users are accessing. What is it or give
some description of its nature -- eg., database app? http? nfs?

Regardless, 256 MB seems rather constipated for any but the simplest
app. My desktop here on an old PII350 has that. You are dipping into
swap for about 15MB but mine using 8+, so that doesn't seem too bad.
Is the server running strictly in console/text mode? What does ps tell
you about running apps?

Also know that some older SMP / multi-threaded apps were not written
that well and that the kernel (2.6) has changed substantially since 2.4
especially re: SMP/multi-threaded apps.

BTW, Linux will always use as much ram as you have (well, within
limits) rather than letting it lie about unused. And ram is _always_
much faster than swap -- and these days it's still pretty cheap.

Unless you can give some past experience with this box and Linux, I'm
inclined to suspect you need to tune Linux + app or confirm that the
app is properly designed to run well in the 2.6 kernel. Just a guess
though. And double check your nic setup -- 100Mbs at full-duplex
_should_ be OK while half-duplex is a killer (especially at 10Mbs).
hth,
prg
email above disabled

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