Date: Fri, 14 Sep 2001 07:27:24 -0500 (CDT) From: "Stephen D. Spencer" <bsd-stable@boneyard.lawrence.ks.us> To: ian j hart <ianjhart@ntlworld.com> Cc: "stable@FreeBSD.ORG" <stable@FreeBSD.ORG> Subject: Re: kernel oplocks Message-ID: <Pine.BSF.4.10.10109140715160.5380-100000@madeline.boneyard.lawrence.ks.us> In-Reply-To: <3B9FE8D6.40EBB7E@ntlworld.com>
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On Wed, 12 Sep 2001, ian j hart wrote:
> Date: Wed, 12 Sep 2001 23:59:34 +0100
> From: ian j hart <ianjhart@ntlworld.com>
> To: "stable@FreeBSD.ORG" <stable@FreeBSD.ORG>
> Subject: kernel oplocks
>
> Samba now comes configured with kernel oplocks enabled by
> default, implying this is part of the kernel. Can someone
> confirm the status of this. ie is it established, or is it
> a new feature. I wouldn't mind knowing where the source is.
> A quick search revealed nothing.
>
I just went through this over the last couple weeks.
Currently, the only systems that currently support kernel
oplocks are IRIX and Linux 2.4.x. Without kernel oplocks,
samba has support for generic user-land oplock support.
This support is broken... something about spinning fcntl
locks if I remember correctly. At any rate, explicitly
turning oplocks off will do away with the error messages
and (if you haven't seen them yet) the eventual freezing
up of your smbd process.
From my research, it appears that oplocks are a performance
feature that alots file/record(?) locking capabilities to the
client for as long as that client is the only system
accessing the file in question. (does away with the latency
of going over the network to do file/record(?) locking. I'm
not an expert on this subject, so I would send you elsewhere
for a definitive description on what oplocks are.
The Using Samba O'Reilley book is included with the samba docs
and includes a description and some diagrams involving
how oplocks work and what they are for)
If someone else comes along and accesses the file, the server
is supposed to force the client to give up its oplock and go
back to the server for locking operations. At any rate,
there have been a number of commits to oplock.c since the
release of 2.2.1a in July. I'm waiting for these updates
to either settle or for 2.2.2 to come out before re-enabling
oplocks. In the mean time, our file server being the big,
beefy box that it is, is having no difficulty keeping up with
the load sans oplocks.
Stephen Spencer |
| "Mutton yesterday, mutton today, and blimey,
| if it don't look like mutton again tomarrer"
| -Bert
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