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List:       freebsd-alpha
Subject:    Re: SMP is stable now.  Whee! :)
From:       John Baldwin <jhb () FreeBSD ! org>
Date:       2001-04-23 17:54:40
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On 21-Apr-01 Andrew Gallatin wrote:
> 
> John Baldwin writes:
>  > > 
>  > > I'm happy to report that with this patchset, plus the
>  > > cricical_enter/exit changes I just committed, a dual cpu 2100 made it
>  > > through a buildworld last night just fine ;)
>  > 
>  > Woo!  The dual 4100 here is still cranking through a -j 8 world.
> 
> What's the appropriate -j level for an MP box, anyway?
> 
> I just naively used -j 2.  Should I go higher?  I realize going higher
> will be a better stress test, where does the overhead from cache
> pollution & extra scheduling outwheigh the possability of having
> another job whose I/O has completed & is ready to run?
> At least on a modern UP, like my tbird, omitting the -j seems to speed
> things up slightly..

Hrm, I've heard the magic formula 4 * NCPU before.  I.e. -j 4 should be better
on UP even so that there is somthing for the CPU to do while waiting on I/O.

> Drew

-- 

John Baldwin <jhb@FreeBSD.org> -- http://www.FreeBSD.org/~jhb/
PGP Key: http://www.baldwin.cx/~john/pgpkey.asc
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/

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