Re: long-lived tcp connection question

[Eric Dumazet <eric.dumazet@gmail.com>]

On Thu, 2012-03-22 at 17:27 -0500, Josh Hunt wrote:
> On Thu, Mar 22, 2012 at 4:51 PM, Hagen Paul Pfeifer <hagen@jauu.net> wrote:
> > * Josh Hunt | 2012-03-22 11:56:19 [-0500]:
> >
> >>Given things like web sockets with presumably long-lived persistent
> >>tcp connections and a sparse amount of data, I was wondering if there
> >>are currently any mechanisms in the kernel or out of tree projects
> >>which work on reducing the overhead these connections require?
> >>Possibly storing their state after a certain period of inactivity and
> >>then reviving them when work needs to be done? I'm thinking something
> >>along the lines of the state info stored for time-wait sockets and
> >>then the ability to resurrect it on an incoming packet. Keeping
> >>resources around for such connections seems inefficient although
> >>possibly unavoidable.
> >
> > Do you referring to something like this:
> >
> > https://datatracker.ietf.org/doc/draft-ietf-tcpm-fastopen/
> >
> > The Linux code is not released yet, but I know that the required storage
> > overhead is small. Search the IETF email archive for more background
> > information about the topic.
> >
> > Hagen
> >
> 
> No, this deals more with the overhead of establishing a connection.
> I'm asking more about the overhead associated with holding on to
> long-lived connections which may not be doing much.
> 

So what are the actual numbers for this overhead per socket ?