pack vs knit based push syd-london packs 1/4 the time of knits... and SFTP write latency glitch?

[Robert Collins]

On Thu, 2007-08-16 at 09:09 -0400, Aaron Bentley wrote:


> > So Robey, I'm wondering if something is causing glitches with SFTP.
> 
> It might be useful to compare with (dumb) bzr+ssh (maybe ssh itself
> doesn't like small writes?)

bzr+ssh will be slower because it pays RTT on every write to the file
stream the pack is being generated on. This is because the
implementation of RemoteTransport.open_file_stream uses a lambda to do
'self.append(bytes)'.

The quick n dirty buffering I added to the repo pack writing means we're
doing 640 objects per write, which will give us something in the region
of 32-64 K writes, I'm guessing.

That said, yes, testing on bzr+ssh needs to be done, but because I know
its going to hurt, I'm not too keen right now :). But I did spend about
an hour yesterday going through what the bzr+ssh streaming interface for
packs needs with Andrew, so there is a good chance we'll have that
shortly after the knit one lands.

-Rob
-- 
GPG key available at: <http://www.robertcollins.net/keys.txt>.
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