Understanding garbage collection impact
I want to be sure that we configured the tool correctly and are interpreting the results right. There are two helpful dashboards to analyze .Net memory and GC impact - Memory Analysis and Garbage Collection Impact.
On the Memory Analysis dahsboard, Garbage Collection Time .Net averages 40%. According to what Microsoft says it should be less than 5%, so that seems high: 
However Gen2 and Large Heap objects are not growing over time: 
and most of the time seem spent in GC 0 collections: 
What's interesting is that on GC Impact dashboard the bars with and without GC are nearly the same:
My specific question is why high percentage spent in GC has such little impact on performance (according to the later dashboard)? Am I missing something here?
-Stan
Hi Stan,
40% really is not OK anymore. I think you should scale the last dashboard a bit because then the difference between the columns will be more clearly to see. This dashlet shows you the PurePath duration (light red) and the PurePath duration without GC time (dark red). If you take a look at the difference the dark red columns are half of the size of the light red ones - so for me it looks like the ~40% are there but the scaling should be adjusted.
Klaus
Hi Klaus:
I looked at the averages by chaging out to Chart+Table and what was interesting is that if I average by Last 24 hours the difference between PurePaths with and without suspension is 1%. However if looking at Last 6 hours or Last 1 hour it becomes 21% and 62% and so I guess the objective is to lower 40% GC collection time.
-Stan
Hi Stan,
Yes this is exactly what you should start with.
-Klaus
where are the dashboards you are mentioning? are they out of the box? sorry i am new to DT
"dashboards to analyze .Net memory and GC impact - Memory Analysis and Garbage Collection Impact"
Thanks
No need to be sorry - we are happy to help.
Some of these dashboards are accessible through the Start Center (this is the Green Toolbar Icon on the top left). There you can access different dashboards depending on your use case. Check out the ones under "Diagnose".
I also recommend checking out the following dynaLearn Webinar: dynaLearn Webinar - Memory and Thread Diagnostics - February 15, 2012
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