fcntl spinlock in Linux?

[Volker Lendecke]

On Wed, Jan 30, 2013 at 01:40:25PM -0500, J. Bruce Fields wrote:
> Eh, I can't tear myself away: here's one thing to try if you've an easy
> way to test it.
> 
> The following removes the global lock lists and the code that depends on
> them (deadlock detection and /proc/locks), which might break some
> programs.  Then it removes the global spinlock and replaces it by the
> inode i_lock.  Only lightly tested.
> 
> Not acceptable for upstream, but it should tell us the most we could
> gain by breaking up the global lock and fixing deadlock detection.
> 
> Generated against something 3.8-rc2ish, but shouldn't be hard to apply
> to older kernels.

Thanks! I'm coordinating wiht my customer now how to test
this.

If I'm reading this right, it replaces the one central
spinlock with per-inode spinlocks. This will help us scale
further, because we can spread the load. But we will still
have the problem that if we heavily contend on a single
fcntl entry, we will see the thundering herd, right? I'm not
sure this is solvable at all but with some RPC service that
queues things.

With best regards,

Volker Lendecke

-- 
SerNet GmbH, Bahnhofsallee 1b, 37081 Göttingen
phone: +49-551-370000-0, fax: +49-551-370000-9
AG Göttingen, HRB 2816, GF: Dr. Johannes Loxen
http://www.sernet.de, mailto:kontakt at sernet.de

**********************************************************
visit us at CeBIT: March 5th - 9th 2013, hall 6, booth E15
all about SAMBA and verinice, firewalls, Linux and Windows
free tickets available via email here : cebit at sernet.com !
**********************************************************