Not entirely serious, but today, we actually hit this, in production :) The hardware, a dual 2Ghz Xeon with 12Gb RAM with Linux 2.6.1-rc2 coped, and remained responsive. So 20,000 may no longer be outside the realms of what administrators reasonably desire to have.
Index: server/mpm/prefork/prefork.c
===================================================================
RCS file: /home/cvspublic/httpd-2.0/server/mpm/prefork/prefork.c,v
retrieving revision 1.286
diff -u -u -r1.286 prefork.c
--- server/mpm/prefork/prefork.c 1 Jan 2004 13:26:25 -0000
1.286
+++ server/mpm/prefork/prefork.c 7 Jan 2004 21:24:55 -0000
@@ -123,7 +123,7 @@
* some sort of compile-time limit to help catch typos.
*/
#ifndef MAX_SERVER_LIMIT
-#define MAX_SERVER_LIMIT 20000
+#define MAX_SERVER_LIMIT 100000
#endif
#ifndef HARD_THREAD_LIMIT
Holy cow!
Bill
