[Python-Dev] very bad network performance (original) (raw)

Curt Hagenlocher curt at hagenlocher.org
Tue Apr 15 01:41:27 CEST 2008

On Mon, Apr 14, 2008 at 4:19 PM, Guido van Rossum <guido at python.org> wrote:

But why was imaplib apparently specifying 10MB? Did it know there was that much data? Or did it just not want to bother looping over all the data in smaller buffer increments (e.g. 64K, which is probably the max of what most TCP stacks will give you)?

I'm going to guess that the code in question is

            size = int(self.mo.group('size'))
            if __debug__:
                if self.debug >= 4:
                    self._mesg('read literal size %s' % size)
            data = self.read(size)

It's reading however many bytes are reported by the server as the size.

If I'm right with my hunch that the TCP stack will probably clamp at 64K, perhaps we should use min(system limit, max(requested size, buffer size))?

I have indeed missed the point of the read buffer size. This would work.

-- Curt Hagenlocher curt at hagenlocher.org

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