More fun with gprof...
directory_walk is one of the bigger consumers of user-mode CPU time in
the current 2.0 httpd source, due largely to its calls to
ap_merge_per_dir_configs.
For a typical configuration that has one <Directory> config for '/' and
another for
the document root path, it looks like all requests for real files will
follow the
same pattern:
* Initialize per_dir_defaults to be the default_lookups for the vhost
matching
the request
* Merge the configs for '/'
* Merge the configs for the document root path
I.e., the same merge of the / and /document/root configs is happening on
every
request.
Assuming that this configuration style (with a <Directory> block for the
document root path) is indeed common, would it be feasible to precompute
the merge of the '/' configs with the /document/root configs after
initialization
to support optimized handling of this case in directory_walk? In the
implementation
I'm thinking of, the logic in directory_walk would look something like:
if (path begins with sconf->ap_document_root) {
per_dir_defaults = precomputed merged configs for document root;
scan the rest of the path (after the docroot prefix) for
possible additional dir matches;
}
else {
use the current algorithm;
}
Would that sort of optimization make sense, or is it too special-purpose
(or too
incorrect, even) to be generally useful?
Thanks,
--Brian
