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Date:      Thu, 07 Jan 1999 10:15:57 +0000
From:      Karl Pielorz <kpielorz@tdx.co.uk>
To:        current@FreeBSD.ORG
Subject:   Problem with -current, SMP and multiple 'nice' processes?
Message-ID:  <3694895D.37DEEE92@tdx.co.uk>

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Hi,

I'm running -current as of a few days ago, and I've 'rediscovered' a long
standing problem I've had...

I run the RC5 client on my machine (OK, it's probably not that a 'technically
correct' program). The machine is a dual PPro-200 (256Mb RAM), running an SMP
a.out kernel...

I've noticed this in the past, but thought it might have been 'fixed' or
changed by now...

If I run the client once (the client warns threads under FreeBSD aren't SMP
aware etc. - so I tell it I have 1 CPU, and follow their other instructions
{keep reading}).. With this 1 client running at a 'nice' priority level, the
load average goes up to 1.0 - and everything is fine...

If I run the client again {as per RC5's instructions for SMP FreeBSD machines}
the load average goes up to 2.0 (as I'd guess you'd expect), and the machine
performs like a dog...

I have samba, sendmail + a few other bits & pieces running on the machine...
Samba's performance drops from just under 5Mb's a second (via a 100Mb FDX
link) to around 30-40k/sec). Everything else on the machine just 'judders'
along very slowly...

I've noticed this happening when I've been running other 'compute' intensive
apps as well (I have a number of home-brew number crunching programs as well)
- no amount of fiddling with 'nice' and priority levels seems to work...

Is this just a 'symptom' of -current's present handling of SMP? - I know the
machine will bottleneck around the kernel, but none of the programs I'm
running are I/O or Kernel bound...

If the concensus is that it's RC5's client that's 'bad' in someway, I might go
on to write some more 'controlled' test programs etc.

-Kp

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