On Thu, Oct 13, 2011 at 7:33 PM, Kim, Yoonsoo <yesarang.kim@gmail.com> wrote:
Troy,What do you think about providing TCP_NODELAY option at ros::init()and making this option default transport hint for suceeding subscriber or publisherinitialization?Another thought is that nowadays, bandwidth is not a critical resource and alsounlikely to be a major problem source for small message exchanges becausethey do not consume bandwidth greatly but large messages do.2x bandwidth consumption of small messages may not be a visiblebehavior change for most ROS users, IMO.And TCP_NODELAY is highly probable to be a reasonable default for most ofrobot applications, considering that ros_comm is made primarily for robot applications,
- Yoonsoo2011/10/14 Troy Straszheim <straszheim@willowgarage.com>
On Thu, Oct 13, 2011 at 11:02 AM, Edwards, Shaun M. <sedwards@swri.org> wrote:A reasonable question. Maybe it would have been a good decision to
> Troy,
>
> I have ran into this same problem many times when working with sockets. Is
> there a reason not to turn off the nagel algorithm by default. Turning off
> the Nagel algorithm would seem to be the default behavior for small
> messages. This would result in more network traffic, but this is probably
> what is desired (i.e. messages arriving as they are sent, instead of
> buffered).
turn it off by default initially (i.e. a few years ago) or not....
but at this point I'd be very reluctant to subtly change the behavior
of every subscriber in ROSland. Imagine the consternation when pipes
that used to exchange lots of small messages efficiently, suddenly
start to use 2x more bandwidth than they used to.
Of course enabling TCP_NODELAY doesn't guarantee you anything. If you
really absolutely need to process things at 100Hz you'd be doing
things completely differently (i.e. realtime kernel and whatnot).
-t
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