Re: [NFS] [CFT] Improved RPC congestion handling for 2.4.0 (and 2.2.18)

["H . J . Lu" <hjl@valinux.com>]

On Tue, Jan 23, 2001 at 12:00:29AM +0100, Trond Myklebust wrote:
> >>>>> " " == H J Lu <hjl@valinux.com> writes:
> 
>      > I got a report which indicates it may not be a good idea,
>      > especially for UDP. Suppose you have a lousy LAN or NFS UDP
>      > server for whatever reason, some NFS/UDP packets may get lost
>      > very easily while a ping request may get through. In that case,
>      > the rpc ping may slow down the NFS client over UDP
>      > significantly.
> 
> Hi HJ,
> 
> Could you clarify this? Don't forget that we only send the ping after
> a major timeout (usually after 3 or more resends).
> 
> IOW: If the ping gets through, then it'll have cost us 1 RPC request,
> which is hardly a major contribution when talking about timescales of
> the order of 5 seconds which is what that major timeout will have cost
> (Don't forget that RPC timeout values increase geometrically).
> 

Michael Kriss <kriss@fnal.gov> is having this problem. I think this
problem may be very specific to his network setup. I couldn't duplicate
his problem. My guess is for his case, every ping sent is a loss of
a potential working retry packet. He is using Solaris NFS sever with
Linux client. I had an impression that packets from Solaris NFS server
was dropped quite often. I don't know what happened.

-- 
H.J. Lu (hjl@valinux.com)
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