Re: Thread implementations...

Alan Cox (alan@lxorguk.ukuu.org.uk)
Fri, 26 Jun 1998 17:18:34 +0100 (BST)


> > No they just understand the problem where you didnt. Your sendfile is
> > useless for web traffic because the headers and file beginning need to
> > go out in the same writev() to the tcp layer so they dont send a short
> > packet and get Nagled.
>
> Is nagle _really_ that big a deal?

Yes. On a 30mS round trip time the fact Nagle kicks in between headers
and body just took you out of the web server benchmarks completely. You
are now 30mS slower clearing a service, your number of threads has
gone up, your live L1/L2 cache has more in it and your context switch
rate has gone up.

Once you factor in transatlantic paths - 100mS or more Nagle is a
huge deal. Even the TCP slow start behaviour has become a big enough
deal the IETF working group went through months of arguing, simulation
and proving to accept a bigger initial congestion window was valid

Alan

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