Hi All, Can someone please help me understand the below snippet of Garbage Collection logs?
(a) What's the importance of values user, sys and real time values? Should I care about those? For instance in the below snippet, 'user' has a value of 0.79second. My understanding is, * 'real' represents the actual time taken by garbage collector process to actually free up memory i.e. create object graph, and the whole mark-sweep process. * 'sys' represents the time spent in System Space (OS/Kernel related???) * 'user' represents the time spent in User space i.e. application. (b) I can see "Stopping threads took: 0.0001230 seconds" statement in numerous occasions. Even when, GC was not taking place. * What does it mean by 'stopping threads took'? Does it mean, garbage collector process was trying to 'park' all the threads, without interrupting ongoing instructions. So it had to wait for ongoing processing to complete, before it could put the thread in 'park' state? * Why does JVM stop application threads even when we don't see any Full GC events? In my system, full gc event is fired every 60 mins - but I can see the above statement numerous times. Why does that happen? * When we talk about GC Suspension time, our definition is - "time for which application will not process anything. Application kinda hangs". Should we consider these "Total time for which application threads were stopped" also as Suspension time? * Any best practices to reduce the suspension time (apart from GC friendly code)? --------------------------------------------------------------------- 2016-07-22T11:17:35.193+0000: 130991.925: Total time for which application threads were stopped: 0.0014892 seconds, Stopping threads took: 0.0001230 seconds 2016-07-22T11:18:05.192+0000: 131021.924: Application time: 29.9988249 seconds 2016-07-22T11:18:05.193+0000: 131021.925: Total time for which application threads were stopped: 0.0010031 seconds, Stopping threads took: 0.0001281 seconds 2016-07-22T11:18:12.845+0000: 131029.577: Application time: 7.6521209 seconds 2016-07-22T13:01:08.837+0000: 137205.569: [Full GC (System.gc()) [PSYoungGen: 9824K->0K(319488K)] [ParOldGen: 321122K->81024K(589824K)] 33 0946K->81024K(909312K), [Metaspace: 37949K->37949K(1083392K)], 0.1677301 secs] [Times: user=0.79 sys=0.00, real=0.17 secs] Heap after GC invocations=23415 (full 41): PSYoungGen total 319488K, used 0K [0x00000000e7000000, 0x00000000fbc00000, 0x0000000100000000) eden space 299008K, 0% used [0x00000000e7000000,0x00000000e7000000,0x00000000f9400000) from space 20480K, 0% used [0x00000000fa800000,0x00000000fa800000,0x00000000fbc00000) to space 20480K, 0% used [0x00000000f9400000,0x00000000f9400000,0x00000000fa800000) ParOldGen total 589824K, used 81024K [0x00000000b5000000, 0x00000000d9000000, 0x00000000e7000000) object space 589824K, 13% used [0x00000000b5000000,0x00000000b9f20000,0x00000000d9000000) Metaspace used 37949K, capacity 38526K, committed 38952K, reserved 1083392K class space used 3894K, capacity 4047K, committed 4144K, reserved 1048576K } 2016-07-22T13:01:09.005+0000: 137205.737: Total time for which application threads were stopped: 0.1749291 seconds, Stopping threads took: 0.0001236 seconds --------------------------------------------------------- Thank You Rohit *** AXP - PUBLIC *** American Express made the following annotations ****************************************************************************** "This message and any attachments are solely for the intended recipient and may contain confidential or privileged information. If you are not the intended recipient, any disclosure, copying, use, or distribution of the information included in this message and any attachments is prohibited. If you have received this communication in error, please notify us by reply e-mail and immediately and permanently delete this message and any attachments. Thank you." American Express a ajouté le commentaire suivant le Ce courrier et toute pièce jointe qu'il contient sont réservés au seul destinataire indiqué et peuvent renfermer des renseignements confidentiels et privilégiés. Si vous n'êtes pas le destinataire prévu, toute divulgation, duplication, utilisation ou distribution du courrier ou de toute pièce jointe est interdite. Si vous avez reçu cette communication par erreur, veuillez nous en aviser par courrier et détruire immédiatement le courrier et les pièces jointes. Merci. ******************************************************************************
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