[ewg] RE: SDP / TCP_NODELAY

[Jim Mott]

Hi,
  SDP does not keep packet size statistics, but could if people want.
Active connection info can be found in /proc/net/sdp, and the counters
(and parameters) we do keep are in /sys/module/ib_sdp. 

  There are a couple debug options that can be enabled.  If you want to
see per-frame detail, then you need to build with
CONFIG_INFINIBAND_SDP_DEBUG_DATA defined and enable with
/sys/module/ib_sdp/<hmm>/data_debug_leve=1.  Then run something small
and use dmesg to get the details.  You can also enable some debug info
on the normal build by setting debug_level=1 in the /sys/module/ib_sdp
tree.

Thanks,
JIm

Jim Mott
Mellanox Technologies Ltd.
mail: jim at mellanox.com
Phone: 512-294-5481


-----Original Message-----
From: Or Gerlitz [mailto:ogerlitz at voltaire.com] 
Sent: Wednesday, November 21, 2007 7:05 AM
To: Jim Mott
Cc: EWG
Subject: Re: SDP / TCP_NODELAY

Jim Mott wrote:
>   SDP includes support for TCP_NODELAY and TCP_CORK.  At a high level,
> these options control buffering and they seem to be working.  If you
> turn off the nagle buffering algorithm using these options, then sends
> go right away.  This is  how TCP_RR testing with netperf run to
measure
> latency.
> 
>   That is my understanding anyway.  If you have some code that does
not
> seem to be running right, send it along and I will take a look.  

OK, thanks for the info, I will check to see if they still suspect that 
the NO_DELAY does not function as it should and let you know. Is there a

  way to see packet size statistics for SDP without an IB analyzer, do 
you expose some sysfs based statistics etc?

Or.