Watchdog feature in Polygraph-2.8.0

Hello All,

I want to test how file system performance can affect Squid Web Cache 
performance. I decided to test the following file systems: ext3, ext2 
(with options: noatime, async), reiserfs and xfs. Problem is that I don't 
know how to write appropriate workload. I want polyclt robots to increase 
gradually request rate until DUT achieve maximum of acceptable value of 
response time. Then polyclt needs to adjusts local population of robots in 
order to sustain an acceptable value of response time and finally fill the 
cache twice. 

I've spend some time on writing a workload but it isn't so easy. My first 
approach was using Rptmstat but I probably did some mistakes and rptmstat 
didn't work for me. Finally I decided to try a watchdog feature. So, I 
simply copied some parts of standard polymix-4.pg and "include" files and 
build below workload file.



I've ran a short test on Squid Web Cache Proxy. I've used one 4,3GB IDE 
disk for a cache cause I've had no time and equipment to make a productive 
test. However, test like that should shows that file system have influence 
on Proxy performance. Unfortunately my results don't confirm above 
statement.



I'm not confident if I've written workload properly. I wanted to write a 
constant response time workload. I've used two watchdog to control number 
of robots alive. Every 2000 xactions "upSample" watchdog increase populus 
factor by +1% if mean response time is below 300msec. Second watchdog, 
"downSample", every 1000 xactions decrease populus factor by -1% if mean 
response time exceeds value of 400msec. Nothing is done if mean response 
time is between 300msec and 400msec. During the test I observed numerous 
response time spikes. I'm not sure if I selected a valid response time 
window. Moreover I remained throughput as an input parameter which I think 
now is not good idea. In addition to this I set low recurrence in a robot 
section. It seems to me logical that lower hit ratio then greater number 
of disk I/O operations. Perhaps hit ratio should be equal to zero. 

If someone has tested mentioned above scenarios please send me workloads 
or tell me where I've made mistakes. 
Thanks in advance,
Peter