Re: SMP on FreeBSD 6.x and 7.0: Worth doing? freenx@deweyonline.com

On Sat, Dec 22, 2007 at 01:40:00PM +0100, Claus Guttesen wrote:
It appears, though I'd need to instrument the code more to be sure,
that the slowdown is coming from file I/O. Could it be that there
less concurrency or more overhead in FreeBSD file operations than
there is in Linux? Even with SoftUpdates turned on, the cache
volume mounted with -noatime, and aufs (which uses kqueues -- a
FreeBSD invention -- to optimize multithreaded disk access), the
benchmark shows FreeBSD losing out. Why?

I have noticed an entry in GENERIC called

device cpufreq

Could this have any influence on the performance (on FreeBSD)?

I saw this device late in the 7.0 release-process and I since I'm
accustomed to comment out any devices and options I don't need I have
commented this out as well. So I haven't performed any tests with and
without this device.


Cpufreq is for CPU frequency scaling. In the linux world, the cpufreq
daemon allows you to control your cpu speed and voltage using power
profiles and such, which makes it a definite power saving tool for
laptops. The cpufreq driver is already included with the Linux kernel,
so I'm going to assume that they've just implemented the cpufreq driver
in the kernel recently :)

If enabled, it probably would have an impact on performance, however I
have lost the ability to test such a function since my laptop decides
not to POST anymore.

Yes, I did figure out what the purpose of this device was. :-) My
point was that this could lead to lower benchmarks on servers if
GENERIC is used.

--
regards
Claus

When lenity and cruelty play for a kingdom,
the gentlest gamester is the soonest winner.

Shakespeare
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Oh, yeah, I see what you mean now. We have GENERIC and SMP kernel
configs, with the cpufreq driver now, there should be like a LAPTOP
kernel config file with laptop-specific options :P

Once I get my laptop working again, though, I'll try testing it out when
7.0-RELEASE comes about.


Russell Doucette

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