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DragonFly bugs List (threaded) for 2004-11
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Process launch problem with DFLY

From: "Nigel Weeks" <nweeks@xxxxxxxxxxxxxxx>
Date: Thu, 11 Nov 2004 15:24:37 +1100

Hi All,

I ran the cd of  DFLY1.0A on my P4 2.8GHz HT 512MB ram, and things went
really smoothly.

I decided to see if it would handle loads better than FreeBSD 4.10.

I wrote a small program in C++: (hog.cpp)

#include <iostream>

return 0;

Compiled it:
`g++ hog.cpp`

Renamed it:
`mv a.out hog.exe`

And ran 10 of them - no worries
started launching them 10 at a time - started slowing down around 200
copies, but still launching around 20-30 spinlocks per second.

Then the weirdness happened:
at about 1000 copies of the program, process launching became instant!!!
I rapidly starting launching more and more - got to around 1500 copies of
this program.
Then everything got slow....reeeeeal slow.
Tried a 'top' and it took nearly 3 seconds to appear.

I kept on launching processes, then running 'top' to see the load averages,
and noticed something else...

As soon as the load average reaches 1000, the load then drops away to 20 or
so, then climbs back up to 1000
Is this like a 'rev limiter' for the scheduler?

Processes launched while load is low happen instantly, but slow back down
again as the load average creeps back up...any ideas?

Found no upper limit though(not yet, anyway) - 1649 running processes and
still going...

Great work guys!


Nigel Weeks
Tech Support & Systems Developer
71 - 75 Paterson Street
Tasmania 7250
Phone: 03 6336 7234

Any idea about the pheno

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