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Date: Mon, 1 Oct 2007 17:37:10 +1000 (EST)
From: Bruce Evans <brde@optusnet.com.au>
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To: Jeff Roberson <jroberson@chesapeake.net>
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Cc: src-committers@freebsd.org, Kevin Oberman <oberman@es.net>,
	cvs-src@freebsd.org, Jeff Roberson <jeff@freebsd.org>,
	Garance A Drosehn <gad@freebsd.org>,
	Ben Kaduk <minimarmot@gmail.com>, cvs-all@freebsd.org
Subject: Re: cvs commit: src/sys/kern sched_ule.c 
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On Sun, 30 Sep 2007, Jeff Roberson wrote:

> On Sat, 29 Sep 2007, Kevin Oberman wrote:

>> YMMV, but ULE seems to generally work better then 4BSD for interactive
>> uniprocessor systems. The preferred scheduler for uniprocessor servers
>> is less clear, but many test have shown ULE does better for those
>> systems in the majority of cases.
>
> I feel it's safe to say desktop behavior on UP is definitely superior.

This is unsafe to say.

> I 
> think there is no significant difference on UP between 4BSD and ULE

This may be safe to say, but is inconsistent with the above.

> except 
> perhaps in context switching microbenchmarks where ULE falls behind.

It is safe to say that interactive users cannot notice insignificant
differences.  It takes a micro-benchmark to notice possibly-significant
differences of hundreds or even thousands of nanonseconds for context
switching.

ULE may give higher priority to interactive processes, but most loss of
interactivity is caused by blocking on I/O, and there is nothing nothing
a scheduler can do to speed up slow or overloaded devices.

Bruce