sftp performance problem, cured by TCP_NODELAY

Miklos Szeredi miklos at szeredi.hu
Wed Jan 25 06:46:50 EST 2006

> What sort of socket calling pattern was sftp making that had it
> running into issues with Nagle and delayed ACK?

Don't know exactly why Nagle kicks in, but it does so quite early,
after just a couple of READ request/reply pairs.  I can send you
tcpdump output tomorrow.

Or you can try to reproduce it, in my experience on high speed links
sftp-get will usually be slower than scp, in which case you will see
Nagle being the culprit.

Strangely sftp-put is not affected.  Again don't know why.


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