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From André Warnier ...@ice-sa.com>
Subject Re: Tomcat threads, II
Date Fri, 21 Nov 2008 11:38:01 GMT
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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