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

Alexey Popov lol at chistydom.ru
Fri Nov 30 01:07:50 PST 2007


Kris Kennaway wrote:
> One more patch which may or may not help is:
>   http://www.freebsd.org/~jhb/patches/namei_rwlock.patch
> (may also require porting since it was against an older version of 
> 7.0-CURRENT).  When I have tested this in the past it was a performance 
> loss for reasons that I think I understand (basically, it is locally a 
> performance improvement for the name cache but also requires a fixed 
> lockmgr to avoid an overall performance loss), but I don't remember if I 
> tested it in conjunction with the lockmgr patch.
This patch doesn't apply to 7-STABLE because /sys/kern/vfs_cache.c was 
changed significanly since rev. 1.108. I tried to patch it manually but 
don't know what to do with cache_lookup() changes.

>>> There are patches you need to enable it on woodcrest.  They are in my 
>>> p4 branch (kris-contention) but I don't have time right now to 
>>> extract them.
>> I think it would be very useful because I can't see any other ways to 
>> profile FreeBSD on the modern many-cores machines.
> You can extract the changeset from my branch via 
> http://perforce.freebsd.org.  Unfortunately I don't have time to do it 
> myself.
I'll try it if it does not also need porting.

With best regards,
Alexey Popov

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