svn commit: r254380 - in head/sys: kern sys

[Colin Percival]

On 08/15/13 14:34, Ivan Voras wrote:
> On 15 August 2013 22:32, Colin Percival <cperciva at freebsd.org> wrote:
>> No, I wasn't aware that it existed.  Given that this change applies only to
>> parallel operations *on the same vnode* and blogbench seems to have traffic
>> randomly spread between many files, I doubt there would be any difference.
> 
> Maybe it could help a bit on the directories?
> 
> Whatever the problem may be (does FreeBSD still have single-writer +
> multiple readers lock for processes accessing the same vnode?), there
> is a huge difference in performance with blogbench between FreeBSD and
> Linux.

We have a single-writer / multiple-readers lock on *any particular byte*
of a vnode.  The rangelock code is what keeps track of this, and the
locking contention I was reducing was in the rangelock bookkeeping.

-- 
Colin Percival
Security Officer Emeritus, FreeBSD | The power to serve
Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid