needed help in interpreting results

[Duane Wessels]

On Tue, 26 Aug 2008, Piotr Kadziolka wrote:

> Hi,
>
> Some time ago I've made series of tests on Squid-2.5STABLE5. I wanted
> confirm and verify results obtained by Duane Wessels in his book about
> Squid. Duane measured how Squid performace can depends on filesystem
> performance. I took all tests on the same machine in  identical
> environment but I obtained strange results for COSS (coss.png).
>
>
> Could someone interpret this results? Is anyone who can give me
> explaination about this periodical peak in response time? Adjustment
> algorithm in the workload (attached file pm4-pf2.pg) take care about
> misses and hits and take action when value exceeds or fell below,
> respectively, 3.0 and 0.25 sec. At second image (diskd.png) which contains
> trace for diskd there is no similar peak.

Whats the time span of the test?  Any chance that they could be
caused by some daily cron job?  But then you'd kind of expect to
see the effect in the diskd data too.  Also the way that the peaks
take longer to decay make me think that its related to Squid filling
up rather than a system cron job.

Duane W.