SMP stall on process creation

[Tony Mantler]

At 3:00 PM -0600 12/16/2000, Daniel Jacobowitz wrote:
>I've been using a dual G4/500 with the linuxppc_2_5 tree for a couple weeks
>now, and having all sorts of strange problems.  While trying to debug one
>(console corruption on select, and sometimes on boot), I discovered
>something very interesting.
>
>I ran, in zsh, this command:
>% time (for i in {1..100}; do /bin/echo -n; done)
>
>on several machines.  On an old 604e/200:
>  0.52s user 1.25s system 100% cpu 1.759 total
>
>On a dual-450 celeron system:
>  0.15s user 0.18s system 62% cpu 0.530 system
>
>But on the G4:
>  0.07s user 6.24s system 100% cpu 6.302 total
>
>This obviously slows shell scripts to a crawl - forking or execing is being
>severely penalized.  I'm also a little startled by the 100% cpu - this is a
>multiprocessor system, that loop should NOT have been throttling both
>processors.
>
>Does anyone have any ideas?  I'm going to go play with 2.2 SMP and 2.4 UP
>for comparison.
[...]

Just ran this on my 9600/200mp, 2.4.0-test11 (linux-pmac-devel, not
terribly current). time says:
 0.84s user 2.63s system 100% cpu 3.466 total

I bumped the count to 1000, and ran top to verify. Top said (roughly) 16%
user (zsh, top, X), 40% system, 44% nice (seti at home, niced 19), which is
about what it should say with only one CPU throttled.

Not as zippy as it could be, but definatley not hammering both CPUs.


Cheers - Tony 'Nicoya' Mantler :)


--
Tony "Nicoya" Mantler - Renaissance Nerd Extraordinaire - nicoya at apia.dhs.org
Winnipeg, Manitoba, Canada           --           http://nicoya.feline.pp.se/


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