java-jvm usage analytics

  as mentioned in title,i will make  analytics between two tomcats which both running a solr app.

 

1.cases comparison

2.analytics

 

1.cases comparison

tomcat	Xms	Xmx	Xmn	NewRatio	SurvivorRatio	mem used by checking 'top-RES' item	resulted: actual new size
A	6g	8g	1.5g	-	6	4.1g	1.5g
B	20g	20g	-	4	6	4.9g	4g

 these are the jvm allocation by checking 'jmap -heap pid'

 tomcat A

Heap Configuration:
   MinHeapFreeRatio = 40
   MaxHeapFreeRatio = 70
   MaxHeapSize      = 8589934592 (8192.0MB)
   NewSize          = 1572864000 (1500.0MB)
   MaxNewSize       = 1572864000 (1500.0MB)
   OldSize          = 5439488 (5.1875MB)
   NewRatio         = 4
   SurvivorRatio    = 6
   PermSize         = 67108864 (64.0MB)
   MaxPermSize      = 104857600 (100.0MB)

Heap Usage:
New Generation (Eden + 1 Survivor Space):
   capacity = 1376256000 (1312.5MB)
   used     = 782190664 (745.9551467895508MB)
   free     = 594065336 (566.5448532104492MB)
   56.83467785063244% used
Eden Space:
   capacity = 1179648000 (1125.0MB)
   used     = 738672576 (704.4530639648438MB)
   free     = 440975424 (420.54693603515625MB)
   62.61805013020833% used
From Space:
   capacity = 196608000 (187.5MB)
   used     = 43518088 (41.50208282470703MB)
   free     = 153089912 (145.99791717529297MB)
   22.134444173177084% used
To Space:
   capacity = 196608000 (187.5MB)
   used     = 0 (0.0MB)
   free     = 196608000 (187.5MB)
   0.0% used
concurrent mark-sweep generation:
   capacity = 4869586944 (4644.0MB)
   used     = 2786356080 (2657.2762298583984MB)
   free     = 2083230864 (1986.7237701416016MB)
   57.2195570598277% used
Perm Generation:
   capacity = 67108864 (64.0MB)
   used     = 37844912 (36.09172058105469MB)
   free     = 29263952 (27.908279418945312MB)
   56.39331340789795% used

 

 tomcat B

Heap Configuration:
   MinHeapFreeRatio = 40
   MaxHeapFreeRatio = 70
   MaxHeapSize      = 21474836480 (20480.0MB)
   NewSize          = 1310720 (1.25MB)
   MaxNewSize       = 17592186044415 MB
   OldSize          = 5439488 (5.1875MB)
   NewRatio         = 4
   SurvivorRatio    = 6
   PermSize         = 67108864 (64.0MB)
   MaxPermSize      = 104857600 (100.0MB)

Heap Usage:
New Generation (Eden + 1 Survivor Space):
   capacity = 3758096384 (3584.0MB)
   used     = 1372982952 (1309.3785781860352MB)
   free     = 2385113432 (2274.621421813965MB)
   36.53400050742285% used
Eden Space:
   capacity = 3221225472 (3072.0MB)
   used     = 1277111448 (1217.948387145996MB)
   free     = 1944114024 (1854.051612854004MB)
   39.646757394075394% used
From Space:
   capacity = 536870912 (512.0MB)
   used     = 95871504 (91.43019104003906MB)
   free     = 440999408 (420.56980895996094MB)
   17.85745918750763% used
To Space:
   capacity = 536870912 (512.0MB)
   used     = 0 (0.0MB)
   free     = 536870912 (512.0MB)
   0.0% used
concurrent mark-sweep generation:
   capacity = 17179869184 (16384.0MB)
   used     = 1514222648 (1444.0752487182617MB)
   free     = 15665646536 (14939.924751281738MB)
   8.813935844227672% used
Perm Generation:
   capacity = 67108864 (64.0MB)
   used     = 37938264 (36.180747985839844MB)
   free     = 29170600 (27.819252014160156MB)
   56.532418727874756% used

 

2.analytics

  A.from all of info above,we know that :

   RES~new gen-size + one survivor-size+ old gen's used-size + perm used= new eden + 2* survivor + old gen's used + perm used

   so the above tomcat A's RES = 4.1g ~ 1312.5MB + 187.5MB + 2657mb + 36mb= 4193mb 

   that means the total mem used is always couted by base part say 'new size' ,added by actual used old size and used perm size.in fact it's reasonable.

  B.the Xmx is the large size of the heap ,so jvm does not always reach it,but what about Xms?is it the min pre-allocated size guaranteed by jvm ?

  nope,we know,the RES is far less than it.

  C.jvm misc gen allcotion for mem.the tomcat B 's 'actual new size' is 4g >> 1.5g which tomcat A used,but u will find that the actual used mem size is less than the A.

  A current used mem:704+41+2657 ~2.4g

  B 's one:1217+91 +1444 ~ 2.7g

   that means 2.7-2.4=300mb objects have been destroyed in 'new area';

   and the old size used:A/2657 ~ 2 * B/1444, that means the Tomcat A jvm will first come into CMS compared to B;and of course,the A 's new-collection-time is much less than B,about half of time saved,say ~25ms .