rcvbuf option

[atarob]

Maxim Dounin Wrote:
-------------------------------------------------------
> Hello!
> 
> On Tue, Feb 18, 2014 at 02:58:05PM -0500, atarob wrote:
> 
> > The config listen option rcvbuf which maps to the TCP SO_RCVBUF, is
> applied
> > to the listening socket, and not inherited by the accept()ed
> connections. So
> > if you have a high load application where the legitimate request is
> bound to
> > be no more than 4K, for instance, you could save a lot of RAM by
> dropping
> > the default here  without changing it at the system level.
> > 
> > I straced nginx and it does not seem to actually apply the settings
> through
> > a subsequent setsockopt to the accepted socket. Is this intentional
> or an
> > oversight?
> 
> What makes you think that SO_RCVBUF is not inherited by accepted 
> connections?

http://stackoverflow.com/a/12864681

I didn't run it myself, because testing it on one platform isn't enough to
assume either way. But why do you think that it is inherited in general?

Also, these are inherently different settings. Even if it were inherited, to
reduce the 10,000 connections on which I expect 2KB of upload, I have to
drop the listening socket's buffer size? Isn't that used by the OS for
clients that are trying to connect to the listening socket? If so, I
wouldn't want to drop that. In fact, since there is only one (or a few)
listening sockets, I might want to increase that while dropping the accepted
sockets' buffer size.

Thoughts?

> 
> -- 
> Maxim Dounin
> http://nginx.org/
> 
> _______________________________________________
> nginx mailing list
> nginx at nginx.org
> http://mailman.nginx.org/mailman/listinfo/nginx

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,247705,247710#msg-247710