Thanks to all responsible for getting the 2.6.14 kernel out quickly. There
are many important bugfixes and features in this kernel that are relevant to
my work. I look forward to using it starting today!
I have a request. Would it be possible for a knowledgeable person to write
up a little description of some of the following kernel options and what they
REALLY mean and how to use them? I think it would be great to put a brief
"white paper" on the kernel.org site.
In specific, I am referring to the following:
Premptible Kernel Model
No Premption
Voluntary Premption
Premptible Kernel (Low-latency Desktop)
Prempt The Big Kernel Lock
Timer Frequency
100 Hz
250 Hz
1000 Hz
I think it would be helpful for the whole Linux community to get better
hints about the theoretical optimal settings for various types of systems. Saying
that one option is good for "desktops" and another is good for "servers" is
a start, but I'm sure that with just a few more words, you could be much more
helpful to users who are trying to decide what options to select for
compiling.
For instance, I have a number of file servers that send video files out
simultaneously to multiple video editing systems. Each of 10-20 video editing
systems could be reading files from the server (or writing files to the server)
at data rates ranging from 3.5 MB/sec up to 30,40 or 50 MB/sec.
The server ITSELF is rarely running any applications other than Samba,
Netatalk, Software RAID 0, NIC drivers, and fairly low-CPU usage things like the
UPS monitor, 3ware Drivers for Hardware RAID 5, and KDE (which is hardly ever
getting any input from users).
We get really great performance with the 2.6.12 and 2.6.10 kernels. And
typically, CPU usage ranges from 10-20 perecent with many client systems going.
However, we are wondering if it is worth it to try the Preemptible Kernels for
greater responsiveness and perhaps support for more simultaneous streams,
which MUST arrive at the video editing system on time or we get "dropped
frames".
I'm sure it's a similar situtation to Video On Demand servers only our data
rates are much higher per client, so we can't support that many clients as a
VOD system.
We have tested compiling the 2.6.12 kernel with both voluntary preemption
and low-latency preemption. Both seem to work fine, but we haven't
stress-tested them yet because we were waiting for the 2.6.14 kernel to come out.
Could we get into any danger with the preemptible kernels if the system load
gets heavy?
And now that the Timer frequency option has been added, what would be
optimal for such a video server that is not itself running any taxing applications?
Hope to hear from one of the "big guys" on this.
Thanks again for all your great work.
Andy Liebman
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