CURRENT branch and older OSes

[Julien ÉLIE]

Hi Russ,

> I suspect that TCP delayed acknowledgements are in play on BSD/OS, based
> on the Wikipedia article, and so this system is seeing the ACK delay
> problem.  Why this would change with versions of INN I have no idea.

I do not know.  Even the one who gave the patch in October 2007
could not reproduce the problem with the same INN!

    https://lists.isc.org/mailman/htdig/inn-workers/2007-October/015186.html

    "I added the code to set TCP_NODELAY to nnrpd on our new news server
    last year, and it seemed to fix a problem noticed by both me and
    a co-worker, slow downloading of overviews.  I posted about this
    on USENET last week.  In response to some skeptical questioning,
    I ran tests on the weekend.  Running trn, I downloaded the overview
    for a high-volume newsgroup, twice using nnrpd with TCP_NODELAY,
    twice using nnrpd without TCP_NODELAY.  There was no difference
    in speed.

    I don't know what else may have changed between last year and
    this year.  I'm pretty sure I wasn't hallucinating last year,
    but I have no clue under what conditions TCP_NODELAY makes a
    difference and under what conditions it doesn't."



> I'd be inclined to only enable it on BDS/OS if we've not seen the problem
> elsewhere.

But it may be present elsewhere and even depend on circumstances
for a given system.



> Normally, Nagle's algorithm is a performance optimization that we want
> (think collecting the pieces of an OVER reply into one packet).

HDR, OVER and XPAT use stdio and such little pieces are sent with
PushIOb only when they reach the size of BIG_BUFFER, as you once
mentioned.  So it should not affect these replies.
The only replies it will affect are LIST replies (Printf on each line)
but I did not notice a slow on Debian.  With Wireshark, I saw that
there was not a packet for each line but that they were sent grouped,
as though TCP_NODELAY were overriden by another thing elsewhere.

-- 
Julien ÉLIE

« Pour se marier, il faut un témoin comme pour un accident ou un duel. » (Sacha Guitry)