So, as rollout strategy we created a new OEM13c to decommission a 12c. However during the testes, noticed Memory Utilization metric was a lot different between 12c and 13c. Why?
Happens that the Memory Utilization is calculated differently between 12c and 13c, but also seems 13c is more accurate, as per MOS The Host Memory Utilization Percentage Calculation in Enterprise Manager Cloud Control (Doc ID 1908853.1)
Well, those who are familiar with memory use computations in the operating system might become confused when examining the memory use metric data from Enterprise Manager 12c and 13c Cloud Control. Metrics such as Memory Utilization (%) do not have an equivalent in the OS, but OS data will be used in its derivation.
This is the formula used by Enterprise Manager 12.1.0.3 for Linux Memory Utilization (%), for example:
Memory Utilization (%) = (100.0 * (activeMem) / realMem) = 100 * 25046000/99060536 = 25.28 EM Shows : 25.5
* On this, activeMem is Active Memory (Active), and realMem is Total Memory (MemTotal).
Comparing this with MemFree, which is not valid, might provide an impression that utilization is not being accurately represented.
Also, the “OEM13c value” was already collected in OEM12c, but under metric name “Used Logical Memory”. And basically “Memory Utilization” in 12c uses “activeMem” instead of “realMem-(freeMem+Buffers+Cached)”. As per image below.
The formula in place on 13c is exactly the same as used to fix MOS EM 13c: Incorrect Memory Utilization Reported for Linux Hosts in Enterprise Manager 13.1.0.0.0 Cloud Control (Doc ID 2144976.1)
Example:
[root@greporasrv ~]# free
total used free shared buffers cached
Mem: 264087460 257669460 6418000 7657500 461088 11008128
-/+ buffers/cache: 246200244 17887216
Swap: 25165820 3365104 21800716
(100.0 * (realMem-(freeMem+Buffers+Cached)) / realMem)
100*(264087460-(6418000+461088+11008128))/264087460) = 93,22678328
As per OEM13c:
Also, by checking on server using SAR, seems value in OEM 13c is more accurate, indeed:
[root@greporasrv ~]# sar -r Linux 2.6.39-400.294.4.el6uek.x86_64 (greporasrv) 08/29/2017 _x86_64_ (44 CPU) 12:00:01 AM kbmemfree kbmemused %memused kbbuffers kbcached kbcommit %commit 12:10:01 AM 5377540 258709920 97.96 719080 10775828 83876744 29.00 12:20:01 AM 6131220 257956240 97.68 719504 10721084 82467712 28.51 12:30:01 AM 5623060 258464400 97.87 719700 10720972 83456216 28.85 12:40:01 AM 5606572 258480888 97.88 719836 10779108 83228440 28.77 12:50:01 AM 5783256 258304204 97.81 719860 10848644 82925908 28.67 01:00:01 AM 4151148 259936312 98.43 719888 11589048 84400040 29.18 01:10:01 AM 3717000 260370460 98.59 719904 11534336 84838784 29.33 01:20:01 AM 4282412 259805048 98.38 720164 11480792 84047568 29.06 01:30:01 AM 4473128 259614332 98.31 720184 11483604 83857348 28.99 01:40:01 AM 5113136 258974324 98.06 720256 11528492 83036284 28.71 01:50:01 AM 4971036 259116424 98.12 720284 11587956 82955128 28.68 02:00:01 AM 4026540 260060920 98.48 720344 11663184 86489692 29.90 02:10:01 AM 4312916 259774544 98.37 720380 11678316 83834592 28.98 02:20:01 AM 5058980 259028480 98.08 720408 11624028 82876972 28.65 02:30:01 AM 4609908 259477552 98.25 720556 11541392 83871244 29.00 02:40:01 AM 5020668 259066792 98.10 720592 11574912 82887808 28.66 02:50:01 AM 5175916 258911544 98.04 720748 11619572 82725252 28.60 03:00:01 AM 4701236 259386224 98.22 720780 11687100 83421624 28.84 03:10:01 AM 4757976 259329484 98.20 721204 11648864 83298716 28.80 03:20:01 AM 4485280 259602180 98.30 721248 11719272 83299472 28.80 03:30:01 AM 4267068 259820392 98.38 721264 11794688 83683344 28.93 03:40:01 AM 4080264 260007196 98.45 721404 11856796 83863540 28.99 03:50:01 AM 4864276 259223184 98.16 721676 11975372 82735744 28.60 04:00:01 AM 4427284 259660176 98.32 721696 12056676 83450524 28.85 04:10:01 AM 4868184 259219276 98.16 721736 11863420 82860464 28.65 04:20:01 AM 4711608 259375852 98.22 721760 11877192 83205684 28.77 04:30:01 AM 4452764 259634696 98.31 721928 11945108 83515596 28.87 04:40:01 AM 4800700 259286760 98.18 722072 12015444 82681320 28.58 04:50:01 AM 4796588 259290872 98.18 722212 12075496 82703948 28.59 05:00:01 AM 4320164 259767296 98.36 722372 12164956 83390596 28.83 05:10:01 AM 3350940 260736520 98.73 722488 12120116 84525028 29.22 05:20:01 AM 4200236 259887224 98.41 722628 11965996 83510580 28.87 05:30:01 AM 4028020 260059440 98.47 722640 12019516 83720748 28.94 05:40:01 AM 3929740 260157720 98.51 722720 12069520 83632964 28.91 05:50:01 AM 2719452 261368008 98.97 723460 14408924 83745112 28.95 06:00:01 AM 1530448 262557012 99.42 723644 14943264 84618304 29.25 06:10:01 AM 2925268 261162192 98.89 605748 13363596 84792452 29.31 06:20:02 AM 3235532 260851928 98.77 605916 13811664 83516740 28.87 06:30:01 AM 3265640 260821820 98.76 606072 13848028 83385196 28.83 06:40:01 AM 2102756 261984704 99.20 606232 14745508 83638764 28.92 06:50:01 AM 2386376 261701084 99.10 606644 14821232 83118484 28.74 07:00:01 AM 5343496 258743964 97.98 186908 12019804 84375032 29.17 07:10:01 AM 5073472 259013988 98.08 219044 12597104 83579876 28.90 07:20:01 AM 5380380 258707080 97.96 241300 12600412 83107160 28.73 07:30:01 AM 5063504 259023956 98.08 253984 12653840 83373804 28.82 07:40:01 AM 8241032 255846428 96.88 269960 9772232 83072188 28.72 07:50:01 AM 8549616 255537844 96.76 278472 9853288 82646916 28.57 08:00:01 AM 8185864 255901596 96.90 287296 9938816 83179808 28.76 08:10:01 AM 7797504 256289956 97.05 295856 10029904 83464160 28.86 08:20:01 AM 8813696 255273764 96.66 302620 9930672 82081220 28.38 08:30:01 AM 8574984 255512476 96.75 309156 9880124 82557600 28.54 08:40:01 AM 8010072 256077388 96.97 314804 9912220 83241764 28.78 08:50:01 AM 8791112 255296348 96.67 319568 9980532 81787424 28.28
