Hello list. I wonder if anyone here could confirm my suspicions (and lack of understanding) re. batched RPC calls? Especially in the context of NFS reads. --[ Background; Initially I was to believe that for every dispatched RPC call (say an NFS read) a reply message from the server was expected - so that the client can use the XID to match it to the call. However, when capturing traffic using libpcap (tcpdump, wireshark, gulp and in-house software all exhibit this behaviour) during peak workloads (100MB/s read - 1600 64k NFS read calls per second) , later analysis shows that the number of identified RPC replies is significantly less than the number of calls. This is despite libpcap reporting no packet loss at either the NIC or kernel level. For example, using the tshark display filter rpc.msgtyp==0 and rpc.msgtyp==1 respectively; Calls: 250364 Replies: 83419 Calls: 165770 Replies: 48488 Calls: 171208 Replies: 14861 This is against 3 different NFS servers (the last being Linux knfsd). This was, to me, unexpected and so I read more and came across the rather tiny amount of information on RPC batching in the RFCs (section 7.4.1 - a small paragraph). The IBM and Oracle websites also have some info but not much. I have found nothing that enables me to identify batched requests (or rather the replies for a batch) in the protocol itself. Wireshark seems unable to do this also. I realise this is a bit off-topic but I was hoping someone might be able to point me in the right direction? Am I barking up the wrong tree? Is this behaviour expected - am I unable to match calls to replies when batching is used? The IBM website suggests; 'Batching assumes the following: Each remote procedure call in the pipeline requires no response from the server, and the server does not send a response message.' This sounds a bit awkward! It then goes on to suggest that; 'The remote procedure call's time out must be 0' For batched calls. But there is no call timeout in the RPC protocol right? Again, this must be up to the client implementation I suspect? Any help appreciated. Regards, Jim PS. I may well join the Linux RPC mailing list and direct this question at them instead. -- Senior Software Engineer Systems Development Framestore -- 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
