Ben Rockwood wrote:
> I wanted to add one more piece of information to this problem that may 
> or not may be helpful.
> 
> On an NFS client if we just do "ls" commands over and over and over we 
> can snoop the wire and see TCP retransmits whenever the CPU is burned 
> up.  nfsstat doesn't record these retransmits, they are happening lower 
> down.  Here's an example packet exchange:
> 
> Frame Time  Packet                          Time Delta
> 85    7.91  GETATTR Call                    0.00
> 89    8.31   Retransmit of 85               0.407s
> 93   11.81  GETATTR Reply                   3.497s
> 
> 
> When the CPU on the Thumper is "normal" transactions look like this:
> 
> 22:38:16.52564 private.atlantis -> 10.71.165.6  NFS C GETATTR3 FH=0E05
> 22:38:16.52574  10.71.165.6 -> private.atlantis NFS R GETATTR3 OK
> 22:38:16.57938 private.atlantis -> 10.71.165.6  TCP D=2049 S=992 
> Ack=1937283399 Seq=4211323728 Len=0 Win=49640
> 
> 
> When the CPU is tapped out, it looks like this:
> 
> 22:37:50.55974 private.atlantis -> 10.71.165.6  NFS C GETATTR3 FH=0E05
> 22:37:50.96940 private.atlantis -> 10.71.165.6  NFS C GETATTR3 FH=0E05 
> (retransmit)
> 22:37:50.96949  10.71.165.6 -> private.atlantis TCP D=992 S=2049 
> Ack=4211321824 Seq=1937281311 Len=0 Win=49640
> 22:37:53.84858  10.71.165.6 -> private.atlantis NFS R GETATTR3 OK
> 22:37:53.89939 private.atlantis -> 10.71.165.6  TCP D=2049 S=992 
> Ack=1937281427 Seq=4211321824 Len=0 Win=49640
> 
> 
> 
> This finding caused us to re-evaluate the entire network scheme. 
> However, I can't ignore the fact that this only happens when the CPU's 
> are tapped out. Perhaps there is a correlation perhaps not. Just wanted 
> to throw it on there.
> 
> 
> benr.

Thanks for providing more info...

Yeah, i would think its TCP/NFS server dropping packets/not getting to 
processing the packets in a timely matter because it doesn't have enough 
resource (CPU).  There may be network inefficiences in your setup, but i 
think this is simply due to lack of CPU on the server.

eric

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