svn - 通过 SVN 下载小文件快，大文件慢

Question

我正在使用 SVN 通过站点到站点 VPN 下载文件。当下载java/class文件时，速度为400kb/s，但当下载.jar文件时，速度下降至10kb/s。有什么想法吗？

Answer 1

java 文件比 jar 小得多(这是一个大的二进制文件，充当 zip 存档)，平均速度看起来会快得多，因为小文件(几 KB)的下载时间比svn 轮询下载速度。
这给人的印象是高平均速度。

但是对于大文件，svn 有时间多次轮询相同的下载速度，并显示实际速度(在较长的时间内)。

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另一个可能影响速度传输的方面是 double-compression issue在 https session 上:

when OpenSSL is built with zlib, it will automatically compress all data sent over an SSL connection. You can see this in the initial handshake "Client Hello" and "Server Hello" where client and server agree on the compression mechanism to be used.

If the data being sent or received is already compressed, OpenSSL will compress it a second time. This can happen when already compressed binaries like .gif or .zip are sent, or when the server uses gzip encoding for a http response. This can have impact on performance and memory usage.

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Ben Reser添加in the comments :
(Ben 是 Apache Subversion project 和 httpd project 的完全提交者/PMC 成员)

You can actually end up with up to 3 layers of compression.

• The plaintext file may be compressed (user controlled),
• the subversion diff format sent over the network can be compressed (controlled via -c for svnserve and SVNCompressionLevel for httpd),
• and the on disk repository delta format can be compressed (will be configurable in fsfs.conf in 1.9).
  The last bit is known to be a significant drain on compressed file transfer speeds and until 1.9, you can't really do anything about it other than avoiding adding compressed files to SVN.