[Samba] 3.6/SMB2.0 and NT6.0 (Vista/W2K8 not-R2) question

[Jeremy Allison]

On Tue, Aug 23, 2011 at 12:27:19PM -0400, starlight at binnacle.cx wrote:
> Hello Samba Team,
> 
> Have a W2K8 not-R2 (NT6.0) server that compiles code
> served from a CentOS 5.6 server running Samba 3.5.5
> over an Infiniband link.
> 
> Works nice but an 'imake' step that grinds through
> every source file several times takes ten-to-twenty
> times longer than when it runs locally on the Linux side.
> 
> It's apparent that the entire source tree is cached
> in memory by Linux, but that the Windows side retrieves
> every file over-and-over again, a process that uses
> more CPU than anything else so that's the bottleneck.
> 
> Windows oplocks seems like the answer to improving
> performance as it would allow the Windows server
> to cache the files as well.
> 
> >From the MS documentation, it appears there might be some
> oplock support in their SMB 2.0 client.  Is this the case?
> Any chance that oplock-based caching of files that are
> only read will happen on the Windows side if we install
> Samba 3.6 and enable SMB2?

oplocks are supported in MS's default SMB1 client.
You don't need SMB2 for that. The Windows client should
already be using oplocks.

> Also, we disable kernel oplocks in Samba because the
> Linux kernel fakes the NFS-visible modification timestamp
> of files that Samba oplocks for the duration that the
> locks are held.  This causes spurious rebuilds by
> Linux and Unix NFS clients when the code is rebuilt
> at the same time.
> 
> Does setting "kernel oplocks = no" in Samba 3.6 interact
> with the SMB2 oplock feature?  I.E. does it disable
> SMB2 oplocks?

It disables mapping the SMB1/SMB2 oplocks to Liux
kernel leases.

Jeremy.