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?

Robert N M Watson
Computer Laboratory
University of Cambridge

>
>>
>>>>>  The right path forwawrd at this point is to diagnosis the problems
>>>>> and work on fixing them in 8-CURRENT, and assuming they are not
>>>>> highly disruptive, MFC them for FreeBSD 7.1.
>>>>
>>>> I believe at least the bug with lockmgr contention should be fixed
>>>> before release.
>>> Could you point me at the specific proposed change in question?  I
>>> don't think I've seen it come across re@ as a potential merge
>>> request.  Changing locking primitives close to a release is, FYI, a
>>> risky business, as while it may improve performance in specific cases,
>>> we may not have a lot of information about more general cases.  We
>>> also risk opening up previously nascent race conditions in lock
>>> consumers.
>> Kris sent me proof of concept patch that helped much against high
>> lockmgr contention. After applying this patch 8-core server become
>> faster that 4-core. But, again, it's still slower than Linux.
>>
>> Here's the patch:
>> http://lists.freebsd.org/pipermail/freebsd-stable/2007-November/038449.html
>>
>> Here's Kris saying that it helps:
>> http://lists.freebsd.org/pipermail/freebsd-stable/2007-November/038672.html
>>
>> I'm not sure it will help to MySQL and Prostgres, but symptoms are
>> mostly identical.
>>
>> With best regards,
>> Alexey Popov
>> _______________________________________________
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>>
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