Kbase 16176: How to monitor -spin parameter within promon
| Autor |
Progress Software Corporation - Progress |
| Acesso |
Público |
| Publicação |
9/24/2002 |
|
WARNING! Development has determined that running latch statistics from
PROMON and the debghb menu on a daily basis, can be harmful to your
database. Please contact Tech Support before running this script.
How to monitor -spin parameter within PROMON
INTRODUCTION:
=============
DISCLAIMER: The information contained in this Knowledge Base entry is
not supported by Progress Technical Support. It is intended to be
used as you see fit to assist you in obtaining performance information
about your Progress application. Progress Technical Support DOES NOT
HAVE any additional documentation or explanation for the material
contained herein. However, there may be other Knowledge Base entries
related to this subject. If additional assistance or explanation is
required, please contact a Progress knowledgable consultant.
The purpose of the KBase is to provide information on monitoring the
performance of wait on semaphores within PROMON.
WHY YOU NEED TO KNOW THIS:
===========================
This information is provided to assist customers with performance
tuning of the -spin parameter.
PROCEDURAL APPROACH:
====================
In 7.3 PROMON to see Wait on semaphore statistics, enter PROMON, put
in R&D, choose 2. Activity Displays ... , 13. Other
To get latching statistics requires the second "secret" password.
Once in the R&D Main menu type debghb and press enter. Now press 6
and press enter (yes, there is no #6 in the menu). Latch Counts and
Latch times are listed here. To enable Latch times, return to the Top
R&D menu (choosing p returns you to the previous menu). Choose 4.
Admin Functions, 4. Adjust Latch Options. Choices 2 and 3 enable data
collection. This will remain enabled as long as the borker is
running. Therefore it is recommended that you return to this screen
and disable it before exiting PROMON. This will remove unwanted
tasks from the broker. Choose t to return to the top menu. Note that
once "invisible" choice #6 is enabled by entering debghb, it is
always available. It will need to be re-enabled each time PROMON is
entered.
Enabling -spin on an SMP machine will result in "good" value for waits
on semaphores, keeping in mind that when -spin is enabled we are still
using the wait on semaphore mechanism for Transaction End Locks (TXE).
A small amount of wait on semaphore accumulation can occur from many
people logging in at the same time, but the majority of this activity
will be related to the TXE lock when -spin is enabled.
A good approach for tuning -spin is by watching the Latch Timeouts.
To see this data, choose 3. Other Displays from the Main (Top) R&D
Menu. Next choose 1. Performance Indicators. By default, choosing A.
here will give you ten, ten second iterations of sampling. In recent
benchmarking, development was able to tune this down to around 600-700
latch timeouts per 10 seconds. Attempts to push the number lower than
this was not successful due to the disk system bottleneck, however
results have been good. -spin can be tuned on a running server through
PROMON in the Adjust Latch Options screen, which was the same place in
which the latch activity data colletion was enabled.
In a nutshell, once -spin is enabled, the wait on semaphore count can
no longer really be affected (directly). Tuning of -spin should then
turn to watching Latch Timeout and trying to reduce this number. It
is recommended that when tuning -spin to keep an eye on the % of
writes done by the APW's on the Activity Screen in PROMON. Often,
reducing latch timeouts pushes up the update activity to the point
where the apws are no longer keeping up. Usually, that means its time
to evaulate the setting for the bi block size and the bi cluster
size or possible introduce more page writers. In addition, cpu
utilization should be monitored. 99% of the time the disk system will
be the bottleneck, and while you can push up -spin and increase cpu
utilization, there will probably be no benefit and it most likely will
have an adverse affect.
The affects of monitoring and tuning -spin for your system will vary
depending on hardware as well as Operating System configuration.
Therefore, results will not necessarily be consistent on different
platforms or even the same platform with different hardware or
software configurations. "Your milage may vary!"
Progress Software Technical Support Note # 16176