On Thu, Jul 23, 2009 at 02:11:46PM -0400, Andy Adamson wrote: > > On Jul 23, 2009, at 11:10 AM, Rick Macklem wrote: > >>>> I really don't want to enable write delegations until we figure >>>> out how >>>> to enforce them correctly against local (non-nfs) users of the >>>> exported >>>> filesystem as well. In addition to breaking delegations on read >>>> opens, >>>> that means breaking delegations or doing a cb_getattr on >>>> operations like >>>> stat. >>> >>> do you know whether there are local FS where the maintainers at >>> least plan >>> to incorporate delegations? >> >> I'm not a Linux guy, so I'm not familiar with the internal structure, >> but... >> in general, I don't think the problem is with local file systems. >> Usually >> the problem is with local system call access. For example, if a >> process running locally on the server opens a file, the delegation >> should >> be recalled, so that changes done locally on the client get flushed >> back >> to the server. Also, a write delegation allows a client to do byte >> range >> locking locally in the client, so the write delegation needs to be >> recalled before anything gets a byte range lock locally in the server. > > The delegation implementation on the Linux server uses the vfs lease > subsystem, and so is integrated with local access - conflicting opens > done locally do recall delegations. But the last time I looked, the > lease subsystem is not complete as it doesn't recall leases (nor > delegations) on remove, rename, etc. Another problem is that while write > delegations improve performance for certain workloads, they kill > performance for others. Are there any published results yet with real workloads? --b. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
