Call for testers, amd64 only, new scheduler. (fwd)

Jeff Roberson jroberson at
Wed Jun 13 20:38:22 UTC 2007

I'm forwarding this email that I sent to current@ in the hopes that some 
performance minded people will tell me their results with this new 
scheduler infrastructure.


---------- Forwarded message ----------
Date: Tue, 12 Jun 2007 19:28:39 -0700 (PDT)
From: Jeff Roberson <jroberson at>
To: current at
Subject: Call for testers, amd64 only, new scheduler.

This is actually a ULE derivative that I have been discussing for some time. 
It is now stable enough that I would like more people to bang on it and give 
feedback about performance and tell me about any stability problems they 

You can see in the following graph that the ramp-up times for the sysbench 
benchmark have improved although the tail has suffered a little:

The new scheduler is FreeBSD-7.0-ULE-pcpulocks.  On my dual cpu system the 
results are much less ambiguous.  It's a 10-15% win on sysbench across the 
board.  This also improves an artificial thread benchmark included with 
sysbench by 500% on an 8 way and gives us ebizzy numbers on par with or better 
than linux.

It also includes a mechanism that should improve bde's nfs buildworld times, 
although I have not yet verified that.  Hopefully he'll try it as well.  It 
should reduce CPU idle time while also negating the effects of thrashing other 
cpus run queues in the idle thread.

The new patch is at:

You have to change your scheduler to SCHED_SMP.  x86 support is forthcoming. 
Depending on feedback and what re thinks I am going to consider replacing ULE 
entirely with SCHED_SMP or committing this as a seperate scheduler for 7.0.

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