Re: [Fwd: [Fwd: Is sendfile all that sexy? (fwd)]]

[dean gaudet]

On Wed, 17 Jan 2001, Rick Jones wrote:

> > actually the problem isn't nagle...  nagle needs to be turned off for
> > efficient servers anyhow.
>
> i'm not sure I follow that. could you expand on that a bit?

the problem which caused us to disable nagle in apache is documented in
this paper <http://www.isi.edu/~johnh/PAPERS/Heidemann97a.html>.  mind you
i should personally revisit the paper after all these years so that i can
reconsider its implications in the context of pipelining and webmux.

> on the topic of pipelining - do the pipelined requests tend to be send
> or arrive together?

i'm pretty sure the actual use of pipelining is pretty disappointing.
the work i did in apache preceded the widespread use of HTTP/1.1 and we
believed it was important to do the "most efficient thing" right out the
door -- so as to encourage the use of pipelining by proxies in particular.
the w3c folks, henrik frystyk nielsen in particular, provided most of the
documentation for this.  their paper is a good read:
<http://www.w3.org/Protocols/HTTP/Performance/Pipeline.html>

> > (the heuristic i use in apache to decide if i need to flush responses in a
> > pipeline is to look if there are any more requests to read first, and if
> > there are none then i flush before blocking waiting for new requests.)
>
> how often to you find yourself flushing the little bits anyhow?

i'm not aware yet of any study in the field.  and i'm out of touch enough
with the clients that i don't know if new netscape or IE have finally
begun to use pipelining (they hadn't as of 1998).

-dean