What's the actual timespan that determines the term 'recently' used memory

[Xsaron]

Hi

I'm doing some testing with optimizing the memory management of my esxi. Several sources talk about the term 'recently' used memory (f.e. when talking about active memory as in 'allocated memory RECENTLY accessed or used by applicatieons', or idle memory as in 'allocated memory not RECENTLY accessed or used) but they never state what the timespan is that determines if it's recently or not... So, is 'recently' the memory used the last 5 minutes, the last 30 minutes, the last hour ...? I was wondering if anyone can help me with this.

Thanks on advance.

[vmMarkA]

Typically the term "recently" can be replaces with the metric sampling interval.

For example:

In vCenter, the sampling period is 20 seconds so the it would be the active memory (which remember is still only an estimate) within the last 20 seconds.

In esxtop, the sampling period can be changed, but the default is every 3 seconds so in this case it would be the active memory within the last 3 seconds.

Remember active memory is an interesting counter because it is calulated using statistical estimation of touched memory pages (actual counting of those pages would be too inefficient so our algorithm has been proven to be as accurate with less cost).  It does not mean the actual amount of memory the guest is using, but only that the guest touched a number of pages in the last sampling interval.  In the next sampling interval the same number of pages could be touched again but it does not mean they were the same pages.  Make sense?

Active memeory is just one counter that can/should be watched for operatingal monitoring.

[Xsaron]

Ok, thanks for the info!