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Re: Slow Upload Performance on High-Bandwidth connections on windows

From: Gisle Vanem <>
Date: Fri, 01 Feb 2013 13:47:58 +0100

"Christian Hägele" <> wrote:

> The reason for that is the Curl_sndbufset-function in connect.c. On windows the socket-sendbuffer is set to a value of
> CURL_MAX_WRITE_SIZE + 32 (16416 bytes). There is a also a strange comment why this is done.
> When the SO_SNDBUF is not explicitly set the socket-sendbuffer is increased automatically by the OS (starting with windows
> Vista/Server 2008).

Did you also see the comment in include/curl/curl.h? 'CURL_MAX_WRITE_SIZE'
can be set a compile-time. I suggest you do that to not make transfer slower
for people using an older Windows (Win-XP).

The problem described in
doesn't seems to apply to Win-Vista. So do you mean Curl_sendbufset()
should not be set for Vista/2008 R2? If so, there should be an adaption to
the running Windows version. Try it; ref. curl_sspi.c.


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Received on 2013-02-01