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Date: Sun, 26 Dec 2004 02:33:57 -0500 (EST)
From: Jeff Roberson <jroberson@chesapeake.net>
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Subject: Re: cvs commit: src/sys/kern subr_trap.c
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I forgot to mention.  This change was made possible by observing thread
states with schedgraph.py. :-)

On Sun, 26 Dec 2004, Jeff Roberson wrote:

> This causes a slight slowdown with sched_ule because ule depends on extra
> context switches to help out the load balancer.  I'm in the process of
> making a slightly more agressive rebalancer at the moment, after which it
> will be an improvement on ULE as well.  Allowing the thread to continue to
> run even though it is not technically the highest priority thread is
> acceptable in this case because priority propagation ensures that we are
> not running when something as important as an interrupt thread is still
> waiting to run.
>
> On Sun, 26 Dec 2004, Jeff Roberson wrote:
>
> > jeff        2004-12-26 07:30:36 UTC
> >
> >   FreeBSD src repository
> >
> >   Modified files:
> >     sys/kern             subr_trap.c
> >   Log:
> >    - Run sched_userret() after thread_userret().  Before, sched_userret() would
> >      lower the priority of the returning thread to a user priority before
> >      calling into thread_userret() which would call wakeup() which in turn would
> >      cause the returning thread to eventually context switch rather than
> >      completing its slice.  Allowing this thread to complete its slice first
> >      yields a 15% performance improvement in super-smack on my dual opteron with
> >      4BSD.
> >
> >   Revision  Changes    Path
> >   1.277     +4 -5      src/sys/kern/subr_trap.c
> >
>