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ap_request_core_filter issues


On Thu, Oct 18, 2018 at 12:51:06PM +0200, Ruediger Pluem wrote:
> >>>
> >>> Curiously inefficient writev use when stracing the process, though, 
> >>> dunno what's going on there (trunk/prefork):
> >>>
> >>> writev(46, [{iov_base="\r\n", iov_len=2}], 1) = 2
> >>> writev(46, [{iov_base="1f84\r\n", iov_len=6}], 1) = 6
> >>> writev(46, [{iov_base="<D:lockdiscovery/>\n<D:getcontent"..., iov_len=7820}], 1) = 7820
> >>> writev(46, [{iov_base="<D:supportedlock>\n<D:lockentry>\n"..., iov_len=248}], 1) = 248
> >>
> >> The reason is ap_request_core_filter. It iterates over the brigade and hands over each bucket alone to
> >> ap_core_output_filter. IMHO a bug.
> > 
> > How about the attached patch for fixing?
> 
> Scratch that. I guess it is much more complex.

Hmm, well it works for me and looks correct, it batches up those the 
writev(,,1) calls as expected, but it seems YMMV :)

I notice the function is doing unconditional blocking reads without 
flushing first - rule 10 of the golden rules of output filters! --

         status = apr_bucket_read(bucket, &data, &size, APR_BLOCK_READ);