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



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.

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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