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

[Krassimir Slavchev]

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Alexey Popov wrote:
> Hi
> 
> Robert Watson 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

> 
>>>>  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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