Trond Myklebust (trond.myklebust@xxxxxxxxxx) wrote on 2 June 2009 13:27: >Write gathering relies on waiting an arbitrary length of time in order >to see if someone is going to send another write. The protocol offers no >guidance as to how long that wait should be, and so (at least on the >Linux server) we've coded in a hard wait of 10ms if and only if we see >that something else has the file open for writing. >One problem with the Linux implementation is that the "something else" >could be another nfs server thread that happens to be in nfsd_write(), >however it could also be another open NFSv4 stateid, or a NLM lock, or a >local process that has the file open for writing. >Another problem is that the nfs server keeps a record of the last file >that was accessed, and also waits if it sees you are writing again to >that same file. Of course it has no idea if this is truly a parallel >write, or if it just happens that you are writing again to the same file >using O_SYNC... I think the decision to write or wait doesn't belong to the nfs server; it should just send the writes immediately. It's up to the fs/block/device layers to do the gathering. I understand that the client should try to do the gathering before sending the request to the wire. -- 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
