I think I finally found the culprit. At first I thought it was the core_output_filter, but it turns out that emulate_sendfile (incorrectly) assumes that it is at the beginning of the file even when it's not.
The attached patch works here when I have the combo of buckets as described below. The patch is against 2.0.49.
I took a 15 second look at the patch and have a concern (perhaps unfounded). apr_file_seek() is probably an expensive operation. If offset is 0, then in almost all cases (correct me if i'm wrong) the fileptr will be at offset 0 as well, right? So your patch will result in an expensive operation which is not needed most of the time. Is there a different way to fix this?
Bill
