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

[Alexey Popov]

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.

>>>  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