Date: Mon, 1 Oct 2007 02:13:57 -0700 (PDT) From: Jeff Roberson <jroberson@chesapeake.net> To: Bruce Evans <brde@optusnet.com.au> Cc: src-committers@freebsd.org, 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 Message-ID: <20071001020835.B583@10.0.0.1> In-Reply-To: <20071001172620.X1839@besplex.bde.org> References: <20070930040318.094E345018@ptavv.es.net> <20070930153430.U583@10.0.0.1> <20071001172620.X1839@besplex.bde.org>
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On Mon, 1 Oct 2007, Bruce Evans wrote: > 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. Given that the overwhelming amount of feedback by qualified poeple, I think it's fair to say that ULE gives a more responsive system under load. > >> 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. I meant no significant difference in performance. I'm sure there are corner case workloads in favor of one or the other. > >> 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. There is a significant enough class of problems that benefit from the improved interactive priorities that people notice it. I have heard reports from a number of laptop users who can run at lower power levels using ULE. I am trivially able to create workloads where 4bsd falls over well before ULE. It is true that io behavior dominates in many cases but that's really a seperate issue. Jeff > > Bruce >
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