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) difference.

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

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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