Messages in this thread |  | | From | "Shirish Kalele" <> | Subject | Re: [NFS] NFSD over TCP: TCP broken? | Date | Wed, 17 Oct 2001 05:38:31 -0700 |
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Okay, looking at tcp_sendmsg a little more, it looks like it lets go of the sock lock in wait_for_tcp_memory before re-acquiring it, which is probably where the interleaving gets in. I'm not sure if TCP should be handling this or NFSD. From what little I know, TCP should serialize requests it gets and atomically write them out, preventing interleaving, and it looks like it doesn't do that.
- Shirish
----- Original Message ----- From: "Shirish Kalele" <kalele@veritas.com> To: <kernel@vger.linux.org>; <nfs@lists.sourceforge.net> Sent: Wednesday, October 17, 2001 3:50 AM Subject: [NFS] NFSD over TCP: TCP broken?
> Hi, > > I've been looking at running nfsd over tcp on Linux. I modified the #ifdef > so that nfsd uses tcp. I also made writes to the socket blocking, so that > the thread blocks till the entire reply has been accepted by TCP. (I know > the right way is going to be to have an independent thread whose job would > be to just pick replies off a queue and block on sending them to tcp, but > this is what I've done temporarily.) > > Then I tried to copy a directory from a Solaris client to the Linux server > using nfsv3 over tcp. This took a long time, with lots of delays where > nothing was being transferred. > > Looking at the network traces, it looks like the RPC records being sent over > TCP are inconsistent with the lengths specified in the record marker. This > happens mainly when 3-4 requests arrive one after the other and you have 3-4 > threads replying to these requests in parallel. It looks like TCP gets > hopelessly confused and botches up the replies being sent. I point my finger > at TCP because tcp_sendmsg returns a valid length indicating that the entire > reply was accepted, but the tcp sequence numbers show that the RPC record > sent on the wire wasn't equal to the length accepted by TCP. After a while, > the client realizes it's out of sync when it gets an invalid RPC record > marker, and resets and reconnects. This repeats multiple times. > > Is TCP known to break when multiple threads try to send data down the pipe > simulaneously? Is there a known fix for this? Where should I be focussing to > fix the problem? > > I'm not on the list, so please include me in replies. > > Thanks, > Shirish > > > > _______________________________________________ > NFS maillist - NFS@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/nfs >
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