[PATCH] block speed up

[gregames]

I'm interested in doing some scalability testing with worker on Linux to see 
what the O(1) scheduler and new pthread library buys us, and what happens with 
different values for ThreadsPerChild.  I decided to use a simple handler that 
just nanosleep()s for a variable amount of time controlled by the client.  I ran 
oprofile and saw that the kernel's directory lookup function was the top CPU 
eater.  An strace revealed that we were doing a directory walk, resulting in a 
stat() and 7 lstat()s per request.

My config to enable the handler is

<Location /silly>
        SetHandler s2-handler
</Location>
...which is the same way we enable mod_status and mod_info.  The key thing here 
is that the URIs to access a Location enabled handler do not map to the 
filesystem, so the directory walk is a waste of cycles.  So what can we do about 
it?  Maybe detect that the current URI matches such a block, and skip the 
filesystem mapping if so.  That's exactly what this patch does.

Throughput measured by ab increases from 3053 requests/sec to 3984 with this 
patch, slightly more than 30% (dual 400MHz PII, both pegged, 256M RAM, RH 7.3). 
 This should make it easier to see how the OS changes etc affect our scalability.

I really don't grok how the cache works in ap_location_walk so I wouldn't be 
shocked if I haven't implemented this optimally.  But it seems to do the Right 
Thing with the nanosleep handler, mod_status, and static files.  I also 
confirmed that we do get a full directory walk if I type in a garbage URL.

Comments?
Greg
Index: include/http_core.h
===================================================================
RCS file: /home/cvs/httpd-2.0/include/http_core.h,v
retrieving revision 1.77
diff -u -d -b -r1.77 http_core.h
--- include/http_core.h 1 Jan 2004 13:26:16 -0000       1.77
+++ include/http_core.h 14 Jan 2004 22:48:09 -0000
@@ -367,6 +367,8 @@
      * won't actually be delivered as the response for the non-GET method.
      */
     int deliver_script;
+    /* The URI matches a <Location > block containing a SetHandler */
+    int uri_outside_filesystem;
 } core_request_config;
 
 /* Standard entries that are guaranteed to be accessible via
Index: server/core.c
===================================================================
RCS file: /home/cvs/httpd-2.0/server/core.c,v
retrieving revision 1.256
diff -u -d -b -r1.256 core.c
--- server/core.c       8 Jan 2004 18:56:20 -0000       1.256
+++ server/core.c       14 Jan 2004 22:48:09 -0000
@@ -3349,6 +3349,9 @@
 static int core_map_to_storage(request_rec *r)
 {
     int access_status;
+    core_request_config *r_conf = ap_get_module_config(r->request_config,
+                                                       &core_module);
+    if (!r_conf->uri_outside_filesystem) {
 
     if ((access_status = ap_directory_walk(r))) {
         return access_status;
@@ -3356,6 +3359,7 @@
 
     if ((access_status = ap_file_walk(r))) {
         return access_status;
+    }
     }
 
     return OK;
Index: server/request.c
===================================================================
RCS file: /home/cvs/httpd-2.0/server/request.c,v
retrieving revision 1.132
diff -u -d -b -r1.132 request.c
--- server/request.c    1 Jan 2004 13:26:23 -0000       1.132
+++ server/request.c    14 Jan 2004 22:48:09 -0000
@@ -1330,9 +1330,22 @@
      * and note the end result to (potentially) skip this step next time.
      */
     if (now_merged) {
+        core_dir_config *core_dir_conf = ap_get_module_config(now_merged,
+                                                              &core_module);
+        core_request_config *r_conf = ap_get_module_config(r->request_config,
+                                                           &core_module);
+
         r->per_dir_config = ap_merge_per_dir_configs(r->pool,
                                                      r->per_dir_config,
                                                      now_merged);
+        if (core_dir_conf->handler && strcmp(core_dir_conf->handler,
+                                             "none")) {
+            /* this location block has a handler.  A pretty strong hint
+             * that this URI doesn't live in the filesystem
+             */
+            r_conf->uri_outside_filesystem = 1;        
+        }
+            
     }
     cache->per_dir_result = r->per_dir_config;