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Can someone tell me how Memory Used and Memory Usable from the Host Montoring Agent correlates to what is presented by the Linux free command

dan_m_smith
Helper

[dsmit643@sldcapild001310 ~]$ free
total used free shared buff/cache available
Mem: 7748236 2740424 390056 40516 4617756 4561612
Swap: 2096444 276452 1819992

From dynaTrace

Timestamp - Memory Usable - sldcapild001310.softlayer.com Value
2015-11-12T09:39:10 4318855168
Timestamp - Memory Used - sldcapild001310.softlayer.com Value
2015-11-12T09:39:10 3615338496

6 REPLIES 6

patrick_thurner
Dynatrace Pro
Dynatrace Pro

our metrics relate to the buffer values of the free command which are more meaningful (http://serverfault.com/questions/85470/meaning-of-the-buffers-cache-line-in-the-output-of-free). Usable then refers to the available (free) buffer

dan_m_smith
Helper

I agree the Buffers line is more meaningful. In my example, this variant of Linux or free does not present the Buffers information. It combines buffers/cache into one value.

[dsmit643@sldcapild001310 ~]$ free

total used free shared buff/cache available
Mem: 7748236 1042376 301076 29692 6404784 6353468
Swap: 2096444 30360 2066084

On other variant, when free presents the Buffers line I can understand the dynaTrace memory numbers. But in this case I cannot figure what calculation dynaTrace is making.

I'll attach a working spread sheet.

Thanks for your help.

Dan

dynatrace-memory-calculations.xlsx

dan_m_smith
Helper

Hello again, I'm still not clear how to reconcile dynaTrace Memory Used/Useable with the output of free on my systems. free indicates Used=609/7566 with 6605 Available. But dynaTrace reports 91% Used.

patrick_thurner
Dynatrace Pro
Dynatrace Pro

Hi Dan,

we'll have a look into it. I'll keep you updated!

dan_m_smith
Helper


This article looks pertinent. Have you heard anything back from your developers?



http://www.logicmonitor.com/blog/2014/10/09/more-linux-memory-free-memory-that-is-not-free-nor-cache...


Thanks

Dan

dan_m_smith
Helper