Messages in this thread | | | Date | Wed, 1 Dec 1999 10:28:24 +0000 (GMT) | From | "Mark O'Neill" <> | Subject | Re: Help with non-standard mod to NFS Kernel daemon ... |
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FYI it doesnt work! But I been supplied a patch by the LINUX supercomputer people which DOES supply the required semantic. Thanks for yr help!
Mark
On Wed, 1 Dec 1999, Neil Brown wrote:
> On Tuesday November 30, rodmur@maybe.org wrote: > > On Tue, Nov 30, 1999 at 04:55:52PM +0000, Mark O'Neill elucidated: > > > One of the nicest aspects of this system is a shared heap model which > > > permits processes to use mmap() (as opposed to sbrk() to create and share > > > data heaps. The problem is while this works very nicely if the > > > co-operating processes are on the same machine, it fails under NFS because > > > user processes on a client machine cannot tell the NFS kernel daemon on > > > that machine to flush all cached data back to the physical file on the > > > NFS server. How hard would it be to implement an additional system call > > > [say nfssync()] to perform this function? Typically this would not impinge > > > on NFS filesystem performance, as this (slow) operation would only need to > > > be called when a process has finished modifying a shared heap in order to > > > provide up-to-date data for other clients of that heap. > > > > > Well... it should work. An 'fsync' on the client tells the client > kernel NFS implementation to send any cached write requests to the > server, and when the server receives the write request, it is required > by the protocol to store it to "stable storage" before repling to the > request. So after an fsync (or close) on the client, all the data > should be safe on disc on the server. > > However, the linux kernel nfsd has an option (which is unfortunately > the default) to allow it to return before the data is safe. This > makes NFS server faster (20%?) but less safe. > If you export with the "sync" export option, it should write data > safely do disc before returning. > > Does this address your problem? or did I miss something. > > > > > I wonder if it would be better to use CODA, or similar shared FS, as > > opposed to NFS in this situation. > > I don't think CODA would be an answer. From my understanding, it > doesn't allow shared write access to a file (the file gets copied, > whole, to which ever client has it open). > > NeilBrown >
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