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From "Bill Barker" <>
Subject Re: useSendFile=true skips compression
Date Sat, 04 Oct 2008 02:43:29 GMT

"Shaun Senecal" <> wrote in message
> Could someone explain to me why the NIO Connector will ignore the
> compression settings for large files if useSendFile is enabled (it is by
> default)?  It seems to me that if compression is enabled you would
> specifically want to use it when sendFile is enabled, but that might just 
> be
> because I don't really understand what sendFile means/does :)

In "normal" mode, Tomcat reads the file into its own memory buffer, 
optionally compresses it, and then writes it out again to the socket.  In 
"sendFile" mode, Tomcat tells the O/S to transfer the contents of the file 
directly to the socket (bypassing reading it in to Tomcat memory).  On a 
modern O/S, this allows the O/S to transfer data using kernel memory only, 
instead of copying the kernel memory to program memory first (which has a 
significant cost on high-volume servers).

> It looks like my solution is to simply disable this option, but I was
> curious about why this is the case.  I am trying to deploy a large GWT 
> app,
> and I want to ensure that my massive JavaScript files get compressed 
> before
> being sent to the client.

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