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Date:      Sun, 2 Mar 2008 21:59:58 +1100
From:      Peter Jeremy <peterjeremy@optushome.com.au>
To:        Jeff Roberson <jroberson@chesapeake.net>
Cc:        cvs-src@freebsd.org, src-committers@freebsd.org, cvs-all@freebsd.org
Subject:   Re: cvs commit: src/sys/kern sched_ule.c
Message-ID:  <20080302105958.GF67687@server.vk2pj.dyndns.org>
In-Reply-To: <20080301222513.Y920@desktop>
References:  <200803020821.m228L0Yw042389@repoman.freebsd.org> <20080301222513.Y920@desktop>

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On Sat, Mar 01, 2008 at 10:29:50PM -1000, Jeff Roberson wrote:
>With these changes ULE is the only scheduler that supports the new cpuset=
=20
>api.

Excellent work.  I didn't expect it to be implemented so quickly.

>  It succeeds on 4BSD but the scheduler doesn't obey the masks. I don't=20
>presently have a plan to implement it on 4BSD as it will be potentially=20
>very inefficient to search the runq for a compatible thread on every=20
>context switch.  I won't object if someone else wants to implement this,=
=20
>otherwise I'll make the syscalls return ENOSYS if 4BSD is compiled in.

I would prefer to see the project devote available resources to
improving ULE - with a view to deprecating 4BSD ASAP - rather than
retrofitting new features into 4BSD.

IMHO, it's not clear whether requests via the cpuset API should be
mandatory or advisory - I believe valid cases can be made for either
approach.  In the latter case, it would be more reasonable for the
cpuset implementation on 4BSD to just be a no-op, rather than failing.

>Kris has done some excellent benchmarking as usual.  Here you can see the=
=20
>improvement in postgres depending on various scheduler debug settings:
>
>http://people.freebsd.org/~kris/scaling/pgsql-16cpu.png

The improvement is quite substantial.  Congratulations Jeff.

--=20
Peter Jeremy
Please excuse any delays as the result of my ISP's inability to implement
an MTA that is either RFC2821-compliant or matches their claimed behaviour.

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