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

Kris Kennaway kris at FreeBSD.org
Wed Nov 21 11:49:39 PST 2007

Alexey Popov wrote:
> Hi.
> Kris Kennaway wrote:
>>> In the meantime there is unfortunately not a lot that can be done, 
>>> AFAICT.  There is one hack that I will send you later but it is not 
>>> likely to help much.  I will also think about how to track down the 
>>> cause of the contention further (the profiling trace only shows that 
>>> it comes mostly from vget/vput but doesn't show where these are 
>>> called from).
>> Actually this patch might help.  It doesn't replace lockmgr but it 
>> does fix a silly thundering herd behaviour.  It probably needs some 
>> adjustment to get it to apply cleanly (it is about 7 months old), and 
>> I apparently stopped using it because I ran into deadlocks.  It might 
>> be stable enough to at least see how much it helps.
> Sorry, I didn't try you patch yet but I have other news.
> As mentioned in the description of your patch there is probably a 
> scalability problem with stat() syscall on FreeBSD.

Not as such, that was just a random example I chose to illustrate the 
lockmgr problems I described earlier.

Try the patch I posted, it should help.


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