Subject: Re: Thread benchmarks, round 2
To: Kris Kennaway <>
From: Kris Kennaway <>
List: tech-kern
Date: 10/05/2007 21:08:07
Kris Kennaway wrote:

> The 4 thread performance is basically identical to the 8 CPU case, 
> showing that the FreeBSD scaling graphed on 8 CPUs is the same as on 4 
> CPUs (but without the tail since mysql contention is now rate-limited), 
> i.e. FreeBSD is continuing to scale linearly.
> This measurement shows that FreeBSD is performing 70-80% better than 
> NetBSD in this 4 CPU configuration.  This is in contrast to Andrew's 
> findings which seem to show NetBSD performing 10% better than FreeBSD on 
> a 4 CPU system (a very old one though).
> I will try later with the experimental kernel Andrew sent me (which 
> includes the new scheduler).  If it indeed gives a 100% performance 
> improvement that would be a significant result :-)

OK, I have repeated the benchmarking in two additional cases:

1) NetBSD with 8 CPUs and some kind of experimental kernel that Andrew 
gave me (based on the vmlocking branch).  This is using the new scheduler.

2) As above with experimental libc and libpthread also given to me by 
Andrew.  I dunno what changes these contain either :)

I was only able to run in the 8 CPU configuration because when I tried 
to disable CPUs with cpuctl, processes would hang under load.  This is 
probably a scheduler issue.

This shows some improvement but not much, relatively speaking.  In 
particular performance at 4 threads is still significantly below FreeBSD 
performance, which (given what I measured previously) suggests that 
there is still a performance deficit with 4 CPUs on NetBSD.  It would be 
nice to be able to test this directly though, maybe Andrew can give me a 
kernel that has MAXCPU=4 or whatever the NetBSD version is.