NCSA httpd 1.3 on the HP3000

Frequently Asked Questions

(under construction)

Are there known problems with httpd 1.3?

Yes, but nothing too serious. Most are limitations inherent in Posix on 5.0 and not unique to the httpd software. The following problems are known as of December 1995, MPE/iX 5.0 Express 2 release:

If you plan on using symbolic links (in httpd or otherwise) there is a known problem that can cause the system to hang in a loop. Refer to SR 5003-243444, patch is MPEHXE0.
Low memory, high system volume set fragmentation, and other conditions can cause program aborts in malloc() with a VSM Data Protection Trap (traps 68). Refer to SR 4701-275941, patch is MPEHXB5.
After installing the above patch, you may get spurious errors "Resource busy - try again" during fork(), exec() and other operations. This can be caused when the largest available contiguous area on ANY system volume drops below ~1024 sectors. Refer to SR 5003-278325. There is no fix at this time. This is not caused by the patch above, the MPEHXB5 simply replaces the VSM abort with the "Resource busy" signal for the same condition.
Network transport may hang after several days of continuous network operation and/or a low number of configured TCP connections in NMMGR's NETXPORT.GPROT.TCP screen. This problem manifests itself by refusing connections and failing even local NS services with a "transport not started" error. None of the "usual" tools show any sign of a problem, but if you take a system dump, all available TCP connections will be "hung". Refer to SR 4701-308304, a beta patch is available NSTED54. This problem is either unique to, or at least very sensitive to httpd.
Poor performance on slower machines (935, 950, 955, etc) apparently due to fork() overhead in MPE/iX 5.0. For each httpd request (one request for a given page, plus one request for each in-line image in the page) the server must fork() a child to service the request. On a 950, this is around a second of CPU; on a 960 about a half-second. As a worst-case benchmark, the OpenDesk documentation is now available in HTML format, the manual index page contains 31 in-line images (5 short-cut icons and one icon for each letter of the alphabet). This page takes over a minute to load from a 950 to a PC on the same ethernet segment. The same page on a small 386/33 Windows PC (running Winhttpd) will load in 3-4 seconds. MPE/iX 5.5 is reported to address the fork() performance issue but the degree of improvement is at this point unknown.

Jeff Kell <jeff@utcvm.utc.edu>

December 1995