Difference Between Perf Data Reported by Different Tools – 2

Interesting Finds: December 12, 2006

Jason Haley — Wed, 13 Dec 2006 07:25:22 GMT

re: Difference Between Perf Data Reported by Different Tools – 2

Marteen Rojo — Fri, 29 Dec 2006 00:15:24 GMT

Dear Maoni,

its with great interest that I've been reading your blog posts.

We are sizing/capacity planning my company's application's performance,

So for each application-centric object we create, memory is measured (so as to figure out how many we can create etc.).

Can you explain the difference between these 2 performance counters?

Process\Private Bytes and

.NET CLR Memory \ # Total committed Bytes ?

I thought that Process\Private Bytes showed , basically, how much memory was actually in use, but now I think the "# Total committed Bytes" is what should be measured.

Sincerely,

Marteen

re: Difference Between Perf Data Reported by Different Tools – 2

maoni — Fri, 29 Dec 2006 12:35:00 GMT

Marteen, the .NET CLR Memory\# Total Committed Bytes is only the private bytes used for *managed heap*. In your process you have other things that will contribute to the private bytes like if you make native allocations either yourself or in some modules that you use and Process\Privates Bytes shows all private bytes used in the process.

re: Difference Between Perf Data Reported by Different Tools – 2

leoleo — Tue, 16 Jan 2007 06:32:57 GMT

This is really interesting, so it looks like the heap sizes from perf counters will always be smaller than !sos.eeheap -gc. For one it doesn't include gen0 but that's a small portion relatively speaking but also it is post GC data which means the heaps are all "cleaned up". Does that sound about right?

re: Difference Between Perf Data Reported by Different Tools – 2

maoni — Tue, 16 Jan 2007 07:05:39 GMT

Yes.

re: Difference Between Perf Data Reported by Different Tools – 2

Mak — Mon, 18 May 2009 20:06:12 GMT

Maoni,

What does it mean if .NET CLR Memory \ # Total committed Bytes is much greater than GC Heap Size. I have a case where Total Committed bytes is 150 MB and GC Heap size is 80 MB.

Thanks

Mak

re: Difference Between Perf Data Reported by Different Tools – 2

maoni — Thu, 03 Dec 2009 20:30:16 GMT

Mak, we do leave some space at the end of the ephemeral segment committed 'cause we don't want to decommit it and have to commit it again for allocations. This is what causes the descrepency.