FreeBSD 5.x performance tips (ISC)

Andre Guibert de Bruet andy at
Tue Jan 13 19:41:58 PST 2004

On Tue, 13 Jan 2004, Peter Losher wrote:

> > What state does top report these processes in? On a busy ftp server, I
> > would expect *Giant, getblk, biord or select. What kind of load averages
> > are you seeing under load, and when somewhat idle? If this system is
> > currently contending on Giant, 5.2 will still exhibit this behavior but to
> > a lesser degree.
> Apologies for not mentioning the cvsup server, but most of those processes are
> always reported as *Giant, the top 4-5 ftpd process are also *Giant; the rest
> are either biord, sbwait, or in one or two cases accept.  httpd processes are
> almost all selects.
> The load average w/ a SMP kernel is 1-3, in a non-SMP kernel, it's around 50.

That was around what I was expecting. As more commits push Giant up,
things should be getting better with time. This machine probably won't see
the benefits of all of the work being done until 5.3 unless you're going
to run CURRENT on it.

> > For a little performance boost, try the ZERO_COPY_SOCKETS and
> > ADAPTIVE_MUTEXES combo in your kernel config. It Works Here (TM). :)
> Are you using ADAPTIVE_MUTEXES in a SMP-aware kernel?  Googling on the term
> showed some lockup issues at boot with it.  (and I assume you are still using
> the 4BSD scheduler?)

Yes. I've been using it on two and four-way systems for months on end.
4BSD is my scheduler of choice.

> > Hmmm.....  Peter, I don't know if anyone has advocated this or not, but have
> > you tried the ULE scheduler?  I have been using it on SMP and UNI machines
> > and it seems to do a better job of keeping loads much more in control.
> I remember trying SCHED_ULE at some point but I think that was during the
> vmpanics so it may not have ever gotten a fair shake...

Same experience here. All my machines that do real work use 4BSD.
Hopefully this will change soon.

> Hopefully this illuminates more light on the issue, I will probably try adding
> ZERO_COPY_SOCKETS & ADAPTIVE_MUTEXES later today when the load dies down.

Let me know how things go.


> Andre Guibert de Bruet | Enterprise Software Consultant >
> Silicon Landmark, LLC. |    >

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