sftp performance problem, cured by TCP_NODELAY

Damien Miller djm at mindrot.org
Thu Jan 26 20:42:52 EST 2006

Miklos Szeredi wrote:
> So TCP_NODELAY is already set for interactive sessions.  I hadn't
> noticed that.
> It's actually pretty stupid I think, as Nagle (TCP_NODELAY off) _only_
> makes sense for _interactive_ sessions.

It makes zero sense for interactive sessions - do you really want your
keystrokes delayed?

> So it should be the other way round as it is currently.
> But unconditionally setting TCP_NODELAY should at least cure the sftp
> performance problem.  The patch in comment #9 looks fine.

We can look at turning Nagle off unconditionally after we get 4.3 out
the door.

> Longer term I think you should consider adding "NoDelay" and maybe
> "NoDelayInteractive" bool options, and _not_ setting nodelay on
> interactive sessions by default.

No, we won't be adding any stupid button for people to push.


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