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From Shawn Pearce <...@google.com>
Subject Re: sshd 0.3.0 performance regression
Date Tue, 15 Dec 2009 04:05:10 GMT
Shawn Pearce <sop@google.com> wrote:
> We're seeing a performance regression in SSHD 0.3.0, the throughput
> is about 1/2 of what it was in SSHD 0.2.0.
> 
> Bisecting the problem in git led me to revision 882491, which was
> the bug fix for https://issues.apache.org/jira/browse/SSHD-49.

I committed a few changes that actually improve this situation
considerably, we're now back to where we were with 0.2.0, and even
slightly faster as our write buffer allocation is now better sized
to meet packet writes.

Guillaume, I really didn't follow how the delta in 882491 fixed
SSHD-49's problem.  You changed a bunch of stuff there all at once.
But it seems to me the root cause was using putBytes() and not
putRawBytes(), so the split packets were corrupted with an extra
4 bytes of data due to the unnecessary length being inserted.

The other changes related to buffering everything on the stream
until the application calls flush() seem to me to be completely
unrelated to solving SSHD-49, and actually caused problems for
Commands that write a lot of data and don't ever call flush().

I'm still a bit unhappy with throughput.  I guess I need to dig into
SSHD-54 here.  The throughput still isn't as fast as we'd like it
to be, especially over LAN connections.

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