Platform Specific Notes

# Running a High-Performance Web Server on HPUX

    Date: Wed, 05 Nov 1997 16:59:34 -0800
    From: Rick Jones <raj@cup.hp.com>
    Reply-To: raj@cup.hp.com
    Organization: Network Performance
    Subject: HP-UX tuning tips

Here are some tuning tips for HP-UX to add to the tuning page.

For HP-UX 9.X: Upgrade to 10.20
For HP-UX 10.[00|01|10]: Upgrade to 10.20

For HP-UX 10.20:

Install the latest cumulative ARPA Transport Patch. This will allow you to configure the size of the TCP connection lookup hash table. The default is 256 buckets and must be set to a power of two. This is accomplished with adb against the *disc* image of the kernel. The variable name is `tcp_hash_size`. Notice that it's critically important that you use "`W`" to write a 32 bit quantity, not "`w`" to write a 16 bit value when patching the disc image because the `tcp_hash_size` variable is a 32 bit quantity.

How to pick the value? Examine the output of ftp://ftp.cup.hp.com/dist/networking/tools/connhist and see how many total TCP connections exist on the system. You probably want that number divided by the hash table size to be reasonably small, say less than 10. Folks can look at HP's SPECweb96 disclosures for some common settings. These can be found at http://www.specbench.org/. If an HP-UX system was performing at 1000 SPECweb96 connections per second, the `TIME_WAIT` time of 60 seconds would mean 60,000 TCP "connections" being tracked.

Folks can check their listen queue depths with ftp://ftp.cup.hp.com/dist/networking/misc/listenq.

If folks are running Apache on a PA-8000 based system, they should consider "chatr'ing" the Apache executable to have a large page size. This would be "`chatr +pi L <BINARY>`". The GID of the running executable must have `MLOCK` privileges. `Setprivgrp(1m)` should be consulted for assigning `MLOCK`. The change can be validated by running Glance and examining the memory regions of the server(s) to make sure that they show a non-trivial fraction of the text segment being locked.

If folks are running Apache on MP systems, they might consider writing a small program that uses `mpctl()` to bind processes to processors. A simple `pid % numcpu` algorithm is probably sufficient. This might even go into the source code.

If folks are concerned about the number of `FIN_WAIT_2` connections, they can use nettune to shrink the value of `tcp_keepstart`. However, they should be careful there - certainly do not make it less than oh two to four minutes. If `tcp_hash_size` has been set well, it is probably OK to let the `FIN_WAIT_2`'s take longer to timeout (perhaps even the default two hours) - they will not on average have a big impact on performance.

There are other things that could go into the code base, but that might be left for another email. Feel free to drop me a message if you or others are interested.

sincerely,

rick jones

http://www.netperf.org/netperf/