FreeBSD 5.3 I/O Performance / Linux 2.6.10 | Continued Discussion

Jesper Louis Andersen jlouis at
Tue Jan 25 02:10:17 PST 2005

Quoting Nick Pavlica (linicks at

>   I would like to start addressing some of the feedback that I have
> been given.  I started this discussion because I felt that it was
> important to share the information I discovered in my testing.  I also
> want to reiterate my earlier statement that this is not an X vs. X 
> discussion, but an attempt to better understand the results, and
> hopefully look at ways of improving the results I had with FreeBSD
> 5.x.  I'm also looking forward to seeing the improvements to the 5.x
> branch as it matures.  I want to make it very clear that this is NOT A
> "Religious/Engineering War", please don't try to turn it into one.

Well, I apologize if I came about that way. The fact seems to be that
linux outperforms freebsd in your tests. The question, obviously, is
why? To be able to answer, we need to find the places where the 2 
systems are different. I suggest creating a webpage, possibly as pure
.txt, where all findings are posted. It makes it easier to process
with graphical plotting tools and it lowers the bandwidth we all need
to transfer. 

If I were you, I would drop the measurements of raw performance for a
bit as we wouldn't gain anything from that. Instead, I would begin
to probe the system while the tests are executing. For instance, what
does ``vmstat 1'', ``iostat 1'' and (if applicable ``gstat'') report
when the test is running in the respective operating systems? What about
open filedescriptors (is the limit reached). Does ``systat -vmstat''
show anything odd on FreeBSD while running the tests, etc? I am sure
people can fill in more interesting probes to try. 

Using the probes might alter the outcome of the test, but as we are
not testing for performance, this doesn't matter.

There is a fair chance that something odd show up. On the other hand,
if nothing shows up, we have ruled a lot of possible stuff out.


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