[Linux-cluster] lock_gulm is very slow. why ?

[Ken Preslan]

On Thu, Jul 22, 2004 at 09:53:45AM -0500, Michael Conrad Tadpol Tilstra wrote:
> On Thu, Jul 22, 2004 at 12:53:48PM +0300, Levent Serinol wrote:
> > Hi,
> >  I have done some benchmark tests with postmark(tests repeated many
> > times). There is one client (also it is lock server). and another one
> > which exports it's scsi hard disk with gnbd.
> [snipped a lot of nice data]
> > as you can see nolock results is 2 times (some parts 3 times) faster
> > then with locked one .
> > what could be the problem ? is there any workaround or settune option
> > (releasing locks earlier,etc...) ?
> 
> the biggest thing you are probably running into is that when running
> with lock_nolock, gfs knows that it is not in a cluster, therefor it can
> enable some optimisations that only work for lcoal filesystems.  These
> optimisations would corrupt disk data if you had multiple nodes mounted.

You can turn off those optimizations with lock_nolock by mounting with
"-o ignore_local_fs".  That will let us figure out what is optimizations
and what is lock latency.

> There is also no network traffic for handling lock in lock_nolock, but
> that is minor compaired to the local file system optimisations.
> 
> Basically, gfs with lock_nolock should always be quite faster than with
> any cluster locking (lock_gulm or lock_dlm).
>
> Ken could say more on this.
> 
> -- 
> Michael Conrad Tadpol Tilstra
> Reality is for people who lack imagination.



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-- 
Ken Preslan <kpreslan at redhat.com>