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From Philip Gladstone <>
Subject Re: Performance of TransmitFile on Windows Servers with 2.0.49
Date Mon, 12 Apr 2004 18:35:11 GMT
OK -- I made a mistake in my tests. My XP system had 'enablesendfile 
off', and that was the reason that it went fast. It does appear that 
fiddling with those flags (TF_WRITE_BEHIND) doesn't make much (if any) 

THe only thing that makes much difference is the MAX_SEGMENT_SIZE. 
Increasing this improves the situation (as it reduces the number of 
200ms pauses). However, there is an effective upper limit of 16MB due to 
the way that the apr_sendfile is used. Even at that level, I can only 
get 8MB/sec versus 11MB/sec for enablesendfile off.

However, in all cases, it really does appear that the 'enablesendfile 
off' can transfer data at a higher data rate.

Sorry about raising false hopes.


Philip Gladstone wrote:

> Bill,
> That patch works when the server is running on XP SP 1. It doesn't help 
> when the server is NT4 SP6. I suspect that the TF_WRITE_BEHIND flag is 
> not supported on that platform.
> When the server is XP, the data rate jumps up to 11MBytes/sec on a 
> 100Mbit network. I would call this a success.
> Philip
> p.s. Is it possible to build with VS.NET? I had to hunt down an old 
> machine with VC6!

Philip Gladstone                    978-ZEN-TOAD (978-936-8623)
Cisco Systems, Inc                                  Boxboro, MA

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