[Lustre-devel] Queries regarding LDLM_ENQUEUE

[bzzz.tomas at gmail.com]

On 10/20/10 6:51 PM, Paul Nowoczynski wrote:
> Eric makes a good point in that only parallel jobs really need this
> feature. Unfortunately, at scale the system (both clients and servers)
> *really do* need something like this, especially if we continue pushing
> users to perform N-1 file I/O instead of 'file per process'. I too am in
> agreement that some sort of capability mechanism is the best approach. I
> wonder if this is something that could be done outside of POSIX and
> supported through a parallel I/O library? Perhaps a single application
> threads could make a special open call (/proc magic perhaps?) and obtain
> the glob of opaque bytes which are then broadcast to the rest of the
> client via mpi. Traversing the namespace would be avoided on all but one
> client. In such a scenario I don't feel that enforcing unix permissions
> at every level of the path is needed or sensible, the operation should
> be treated as a simple logical open. The question to the lustre experts
> - can enough state be packed into an opaque object such that the
> recv'ing client can construct the necessary cache state?

could you explain why is it so important to skip intermediate lookups?
those are to be done once, then the clients will do them locally.
is it because your nodes are getting new paths all the time or the nodes
are rebooted very often and lose cache?

thanks, z