[bug #48589] client and server don't set TCP_NODELAY, resulting in high latency of CVS commands

[anonymous]

URL:
  <http://savannah.nongnu.org/bugs/?48589>

                 Summary: client and server don't set TCP_NODELAY, resulting
in high latency of CVS commands
                 Project: Concurrent Versions System
            Submitted by: None
            Submitted on: Thu 21 Jul 2016 10:17:10 PM UTC
                Category: Bug Fix (patch attached)
                Severity: 3 - Normal
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
                 Release: 
         Discussion Lock: Any
           Fixed Release: None
   Fixed Feature Release: None

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Details:

Hi,

I just noticed that the latency for simple CVS commands when contacting a
remote server is quite high, for example on a repository with only one file,
where the server is on the local machine but accessed through a pserver:

$ echo $CVSROOT
:pserver:cf@localhost:/tmp/cvsroot
$ time cvs log bar
cvs log: Logging bar

real    0m0.095s
user    0m0.004s
sys     0m0.000s

The problem is that neither the client nor the server set TCP_NODELAY on the
socket, and given the CVS protocol, this can result in high latency (see
https://en.wikipedia.org/wiki/Nagle%27s_algorithm#Interactions_with_real-time_systems).

The attached patch sets TCP_NODELAY both client and server-side, and results
in much lower latency:

cf@thinkpad:/tmp$ time ~/ccvs/src/cvs checkout bar
cvs checkout: Updating bar

real    0m0.020s
user    0m0.008s
sys     0m0.000s

Cheers,



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File Attachments:


-------------------------------------------------------
Date: Thu 21 Jul 2016 10:17:10 PM UTC  Name: cvs_tcp_nodelay.diff  Size: 3kB  
By: None

<http://savannah.nongnu.org/bugs/download.php?file_id=37982>

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