2 x quad-core system is slower that 2 x dual core on FreeBSD

[Robert Watson]

On Tue, 4 Dec 2007, Krassimir Slavchev wrote:

>>>>> Evidence in-hand seems to suggest that 8 core systems work very well for 
>>>>> most users, and reflect a significant performance increase with 7.0 over 
>>>>> previous FreeBSD releases.
>>>>
>>>> I disagree with that. Heavily loaded Apache, MySQL, Postgres does not 
>>>> work well.
>>>
>>> There is another report for such problems:
>>>
>>> http://blog.insidesystems.net/articles/2007/04/09/what-did-i-do-wrong
>>
>> A casual reading suggests that this article is about FreeBSD 6.2, and not 
>> FreeBSD 7.0.  Am I misreading?
>
> No, But these tests can be performed on FreeBSD 7.0 4/8 core systems.

These are precisely the sorts of tests we have been running.  You can read a 
bit about the test in Kris's BSDCon.tr presentation:

   http://people.freebsd.org/~kris/scaling/7.0%20Preview.pdf

We can't promise improvement on every workload, but we have seen real 
improvements on a great many workloads.  I don't think anyone would argue that 
there isn't more work to be done, but at some point you have to stabilize and 
cut a release so that people can use something in the mean time.  Releasing a 
perfect operating system in ten years helps no one. :-)  The real issue at 
hand is whether we've hit a critical problem that justifies delaying the 
release in order to refine, test, and merge a change of a critical locking 
primitive in the kernel.  Changing locking primitives, as I mentioned in an 
earlier post, is a risky thing: after all, it intentionally changes the timing 
for critical kernel data structures in the file system code.  I've given 
Stephan, the author of the patch, a ping to ask him about this, but late in a 
release cycle, conservativism is the watch-word.

Robert N M Watson
Computer Laboratory
University of Cambridge