Hi.
To implement a recommendation from someone on this list, I took a few
snapshots using "jmap -heap <pid>" while Tomcat was starting up and also
starting up a webapp.
I just ran the jmap command several times at about 5 second intervals,
and redirected the output to a file.
Below if the file content.
What I would like to know now, is how I interpret these numbers.
Is there somewhere a tutorial giving some pointers as to what I am
looking at ?
Or, does anyone feel like making some comments on the data below ?
As a slightly narrower question, how do some of the numbers below relate
to JVM startup parameters such as -Xms, -Xmx, and/or GC-related parameters ?
And, is there somewhere I could find a description of terms used below,
such as "Eden", "New Generation", "Perm Generation" etc.. ?
Thanks in advance.
Output of "jmap" :
using thread-local object allocation.
Mark Sweep Compact GC
Heap Configuration:
MinHeapFreeRatio = 40
MaxHeapFreeRatio = 70
MaxHeapSize = 268435456 (256.0MB)
NewSize = 655360 (0.625MB)
MaxNewSize = 4294901760 (4095.9375MB)
OldSize = 1441792 (1.375MB)
NewRatio = 8
SurvivorRatio = 8
PermSize = 16777216 (16.0MB)
MaxPermSize = 67108864 (64.0MB)
Heap Usage:
New Generation (Eden + 1 Survivor Space):
capacity = 16187392 (15.4375MB)
used = 14485952 (13.81488037109375MB)
free = 1701440 (1.62261962890625MB)
89.48910361842105% used
Eden Space:
capacity = 14417920 (13.75MB)
used = 12716480 (12.12738037109375MB)
free = 1701440 (1.62261962890625MB)
88.1991299715909% used
From Space:
capacity = 1769472 (1.6875MB)
used = 1769472 (1.6875MB)
free = 0 (0.0MB)
100.0% used
To Space:
capacity = 1769472 (1.6875MB)
used = 0 (0.0MB)
free = 1769472 (1.6875MB)
0.0% used
tenured generation:
capacity = 143376384 (136.734375MB)
used = 109058784 (104.00656127929688MB)
free = 34317600 (32.727813720703125MB)
76.06467742972232% used
Perm Generation:
capacity = 16777216 (16.0MB)
used = 9495520 (9.055633544921875MB)
free = 7281696 (6.944366455078125MB)
56.59770965576172% used
using thread-local object allocation.
Mark Sweep Compact GC
Heap Configuration:
MinHeapFreeRatio = 40
MaxHeapFreeRatio = 70
MaxHeapSize = 268435456 (256.0MB)
NewSize = 655360 (0.625MB)
MaxNewSize = 4294901760 (4095.9375MB)
OldSize = 1441792 (1.375MB)
NewRatio = 8
SurvivorRatio = 8
PermSize = 16777216 (16.0MB)
MaxPermSize = 67108864 (64.0MB)
Heap Usage:
New Generation (Eden + 1 Survivor Space):
capacity = 16187392 (15.4375MB)
used = 7146784 (6.815704345703125MB)
free = 9040608 (8.621795654296875MB)
44.15031155111336% used
Eden Space:
capacity = 14417920 (13.75MB)
used = 5377320 (5.128211975097656MB)
free = 9040600 (8.621788024902344MB)
37.29608709161932% used
From Space:
capacity = 1769472 (1.6875MB)
used = 1769464 (1.6874923706054688MB)
free = 8 (7.62939453125E-6MB)
99.99954788773148% used
To Space:
capacity = 1769472 (1.6875MB)
used = 0 (0.0MB)
free = 1769472 (1.6875MB)
0.0% used
tenured generation:
capacity = 143376384 (136.734375MB)
used = 98216248 (93.66631317138672MB)
free = 45160136 (43.06806182861328MB)
68.50238878949548% used
Perm Generation:
capacity = 16777216 (16.0MB)
used = 9495520 (9.055633544921875MB)
free = 7281696 (6.944366455078125MB)
56.59770965576172% used
using thread-local object allocation.
Mark Sweep Compact GC
Heap Configuration:
MinHeapFreeRatio = 40
MaxHeapFreeRatio = 70
MaxHeapSize = 268435456 (256.0MB)
NewSize = 655360 (0.625MB)
MaxNewSize = 4294901760 (4095.9375MB)
OldSize = 1441792 (1.375MB)
NewRatio = 8
SurvivorRatio = 8
PermSize = 16777216 (16.0MB)
MaxPermSize = 67108864 (64.0MB)
Heap Usage:
New Generation (Eden + 1 Survivor Space):
capacity = 16187392 (15.4375MB)
used = 15972760 (15.232810974121094MB)
free = 214632 (0.20468902587890625MB)
98.67407918459008% used
Eden Space:
capacity = 14417920 (13.75MB)
used = 14203296 (13.545318603515625MB)
free = 214624 (0.204681396484375MB)
98.51140802556819% used
From Space:
capacity = 1769472 (1.6875MB)
used = 1769464 (1.6874923706054688MB)
free = 8 (7.62939453125E-6MB)
99.99954788773148% used
To Space:
capacity = 1769472 (1.6875MB)
used = 0 (0.0MB)
free = 1769472 (1.6875MB)
0.0% used
tenured generation:
capacity = 143376384 (136.734375MB)
used = 138744856 (132.3174057006836MB)
free = 4631528 (4.416969299316406MB)
96.76967163574163% used
Perm Generation:
capacity = 16777216 (16.0MB)
used = 9495616 (9.05572509765625MB)
free = 7281600 (6.94427490234375MB)
56.59828186035156% used
using thread-local object allocation.
Mark Sweep Compact GC
Heap Configuration:
MinHeapFreeRatio = 40
MaxHeapFreeRatio = 70
MaxHeapSize = 268435456 (256.0MB)
NewSize = 655360 (0.625MB)
MaxNewSize = 4294901760 (4095.9375MB)
OldSize = 1441792 (1.375MB)
NewRatio = 8
SurvivorRatio = 8
PermSize = 16777216 (16.0MB)
MaxPermSize = 67108864 (64.0MB)
Heap Usage:
New Generation (Eden + 1 Survivor Space):
capacity = 16187392 (15.4375MB)
used = 1958368 (1.867645263671875MB)
free = 14229024 (13.569854736328125MB)
12.098106971153847% used
Eden Space:
capacity = 14417920 (13.75MB)
used = 288528 (0.2751617431640625MB)
free = 14129392 (13.474838256835938MB)
2.0011763139204546% used
From Space:
capacity = 1769472 (1.6875MB)
used = 1669840 (1.5924835205078125MB)
free = 99632 (0.0950164794921875MB)
94.36939380787037% used
To Space:
capacity = 1769472 (1.6875MB)
used = 0 (0.0MB)
free = 1769472 (1.6875MB)
0.0% used
tenured generation:
capacity = 143376384 (136.734375MB)
used = 110665056 (105.53842163085938MB)
free = 32711328 (31.195953369140625MB)
77.18499582190607% used
Perm Generation:
capacity = 16777216 (16.0MB)
used = 9495616 (9.05572509765625MB)
free = 7281600 (6.94427490234375MB)
56.59828186035156% used
using thread-local object allocation.
Mark Sweep Compact GC
Heap Configuration:
MinHeapFreeRatio = 40
MaxHeapFreeRatio = 70
MaxHeapSize = 268435456 (256.0MB)
NewSize = 655360 (0.625MB)
MaxNewSize = 4294901760 (4095.9375MB)
OldSize = 1441792 (1.375MB)
NewRatio = 8
SurvivorRatio = 8
PermSize = 16777216 (16.0MB)
MaxPermSize = 67108864 (64.0MB)
Heap Usage:
New Generation (Eden + 1 Survivor Space):
capacity = 16187392 (15.4375MB)
used = 11620976 (11.082626342773438MB)
free = 4566416 (4.3548736572265625MB)
71.79029209893724% used
Eden Space:
capacity = 14417920 (13.75MB)
used = 9851504 (9.395126342773438MB)
free = 4566416 (4.3548736572265625MB)
68.32819158380681% used
From Space:
capacity = 1769472 (1.6875MB)
used = 1769472 (1.6875MB)
free = 0 (0.0MB)
100.0% used
To Space:
capacity = 1769472 (1.6875MB)
used = 0 (0.0MB)
free = 1769472 (1.6875MB)
0.0% used
tenured generation:
capacity = 143376384 (136.734375MB)
used = 143291656 (136.65357208251953MB)
free = 84728 (0.08080291748046875MB)
99.94090519119244% used
Perm Generation:
capacity = 16777216 (16.0MB)
used = 9495616 (9.05572509765625MB)
free = 7281600 (6.94427490234375MB)
56.59828186035156% used
using thread-local object allocation.
Mark Sweep Compact GC
Heap Configuration:
MinHeapFreeRatio = 40
MaxHeapFreeRatio = 70
MaxHeapSize = 268435456 (256.0MB)
NewSize = 655360 (0.625MB)
MaxNewSize = 4294901760 (4095.9375MB)
OldSize = 1441792 (1.375MB)
NewRatio = 8
SurvivorRatio = 8
PermSize = 16777216 (16.0MB)
MaxPermSize = 67108864 (64.0MB)
Heap Usage:
New Generation (Eden + 1 Survivor Space):
capacity = 16187392 (15.4375MB)
used = 11288952 (10.765983581542969MB)
free = 4898440 (4.671516418457031MB)
69.73916490068319% used
Eden Space:
capacity = 14417920 (13.75MB)
used = 10963768 (10.455863952636719MB)
free = 3454152 (3.2941360473632812MB)
76.04264692826705% used
From Space:
capacity = 1769472 (1.6875MB)
used = 325184 (0.31011962890625MB)
free = 1444288 (1.37738037109375MB)
18.37745949074074% used
To Space:
capacity = 1769472 (1.6875MB)
used = 0 (0.0MB)
free = 1769472 (1.6875MB)
0.0% used
tenured generation:
capacity = 143376384 (136.734375MB)
used = 96137256 (91.68363189697266MB)
free = 47239128 (45.050743103027344MB)
67.05236477438292% used
Perm Generation:
capacity = 16777216 (16.0MB)
used = 9495616 (9.05572509765625MB)
free = 7281600 (6.94427490234375MB)
56.59828186035156% used
using thread-local object allocation.
Mark Sweep Compact GC
Heap Configuration:
MinHeapFreeRatio = 40
MaxHeapFreeRatio = 70
MaxHeapSize = 268435456 (256.0MB)
NewSize = 655360 (0.625MB)
MaxNewSize = 4294901760 (4095.9375MB)
OldSize = 1441792 (1.375MB)
NewRatio = 8
SurvivorRatio = 8
PermSize = 16777216 (16.0MB)
MaxPermSize = 67108864 (64.0MB)
Heap Usage:
New Generation (Eden + 1 Survivor Space):
capacity = 16187392 (15.4375MB)
used = 1835928 (1.7508773803710938MB)
free = 14351464 (13.686622619628906MB)
11.341715824266194% used
Eden Space:
capacity = 14417920 (13.75MB)
used = 705984 (0.67327880859375MB)
free = 13711936 (13.07672119140625MB)
4.896573153409091% used
From Space:
capacity = 1769472 (1.6875MB)
used = 1129944 (1.0775985717773438MB)
free = 639528 (0.6099014282226562MB)
63.857693142361114% used
To Space:
capacity = 1769472 (1.6875MB)
used = 0 (0.0MB)
free = 1769472 (1.6875MB)
0.0% used
tenured generation:
capacity = 143376384 (136.734375MB)
used = 98726496 (94.15292358398438MB)
free = 44649888 (42.581451416015625MB)
68.85826887641413% used
Perm Generation:
capacity = 16777216 (16.0MB)
used = 10651600 (10.158157348632812MB)
free = 6125616 (5.8418426513671875MB)
63.48848342895508% used
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