Hi Poonam, On Thu, Aug 25, 2016 at 12:28 PM, Poonam Bajaj Parhar < poonam.ba...@oracle.com> wrote:
> Hello Vitaly, > > On 8/24/2016 3:55 PM, Vitaly Davidovich wrote: > > > > On Wed, Aug 24, 2016 at 6:29 PM, Poonam Bajaj Parhar < > poonam.ba...@oracle.com> wrote: > >> Also, do you see entries like "*[G1Ergonomics (Mixed GCs) do not start >> mixed GCs, reason:" *in the GC logs which mean that the mixed GCs are >> not happening due to some reason. What is the reason listed with these log >> entries? >> > Hi Poonam, > > Yes, I do see a few those, but only very early in the process lifetime, > and nowhere near the Full GCs. > > 2016-08-24T10:33:04.733+0000: 8.460: [SoftReference, 0 refs, 0.0010108 > secs]2016-08-24T10:33:04.734+0000: 8.461: [WeakReference, 383 refs, > 0.0006608 secs]2016-08-24T10:33:04.735+0000: 8.462: [FinalReference, 4533 > refs, 0.0020491 secs]2016-08-24T10:33:04.737+0000: 8.464: > [PhantomReference, 0 refs, 15 refs, 0.0011945 > secs]2016-08-24T10:33:04.738+0000: > 8.465: [JNI Weak Reference, 0.0000360 secs] 8.467: [G1Ergonomics (Mixed > GCs) do not start mixed GCs, reason: concurrent cycle is about to start] > 2016-08-24T10:35:22.846+0000: 146.574: [SoftReference, 0 refs, 0.0011450 > secs]2016-08-24T10:35:22.847+0000: 146.575: [WeakReference, 440 refs, > 0.0006071 secs]2016-08-24T10:35:22.848+0000: 146.575: [FinalReference, > 7100 refs, 0.0018074 secs]2016-08-24T10:35:22.850+0000: 146.577: > [PhantomReference, 0 refs, 76 refs, 0.0013148 > secs]2016-08-24T10:35:22.851+0000: > 146.579: [JNI Weak Reference, 0.0000443 secs] 146.584: [G1Ergonomics (Mixed > GCs) do not start mixed GCs, reason: concurrent cycle is about to start] > 2016-08-24T10:35:56.507+0000: 180.234: [SoftReference, 0 refs, 0.0010184 > secs]2016-08-24T10:35:56.508+0000: 180.235: [WeakReference, 138 refs, > 0.0006883 secs]2016-08-24T10:35:56.508+0000: 180.236: [FinalReference, > 3682 refs, 0.0023152 secs]2016-08-24T10:35:56.511+0000: 180.238: > [PhantomReference, 0 refs, 45 refs, 0.0012558 > secs]2016-08-24T10:35:56.512+0000: > 180.239: [JNI Weak Reference, 0.0000197 secs] 180.247: [G1Ergonomics (Mixed > GCs) do not start mixed GCs, reason: concurrent cycle is about to start] > > > The above entries should be okay. > > 2016-08-24T10:37:33.387+0000: 277.114: [SoftReference, 0 refs, 0.0010965 > secs]2016-08-24T10:37:33.388+0000: 277.115: [WeakReference, 5 refs, > 0.0006378 secs]2016-08-24T10:37:33.388+0000: 277.116: [FinalReference, > 3440 refs, 0.0028640 secs]2016-08-24T10:37:33.391+0000: 277.119: > [PhantomReference, 0 refs, 0 refs, 0.0011392 > secs]2016-08-24T10:37:33.392+0000: > 277.120: [JNI Weak Reference, 0.0000148 secs] 277.130: [G1Ergonomics (Mixed > GCs) do not start mixed GCs, reason: candidate old regions not available] > > If these appear only during the startup, I won't worry about these too. > > Do you see mixed GCs happening later during the run? If yes, then it's > just that the mixed GCs are not quite enough to keep pace with the > allocations/promotions into the old regions. > > To increase the number of old regions included into the cset, you could > try increasing the value of > *G1MixedGCLiveThresholdPercent.* > So as I mentioned in my earlier email today, we tried using IHOP=55 (instead of 75). There are very long Object Copy and Finalize Marking times now, although the heap cleanup is pretty good. I didn't see any Full GCs with that setting, but the very long Full GC pauses are just replaced by extremely long Finalize Marking times (and fairly long Object Copy times). Thanks > > Thanks, > Poonam > > Does that tell you anything? > > >> >> Thanks, >> Poonam >> >> On 8/24/2016 3:18 PM, Jenny Zhang wrote: >> >> More comments about the questions >> >> Thanks >> Jenny >> >> On 8/24/2016 11:43 AM, Vitaly Davidovich wrote: >> >> Right before the Full GC, ergonomics report a failure to expand the heap >> due to an allocation request of 32 bytes. Is this implying that a mutator >> tried to allocate 32 bytes but couldn't? How do I reconcile that with >> Eden+Survivor occupancy reported right above that? >> >> Yes, it means the mutator tries to allocate 32byte but can not get it. >> Heap won't expand as it already reaches max heap. >> >> Do you see any humongous objects allocatoin? >> >> >> Young gen is sized to 30GB, total heap is 96GB. Allocation rate of the >> application is roughly 1GB/s. Am I correct in assuming that allocation is >> outpacing concurrent marking, based on the above? What tunable(s) would you >> advise to tweak to get G1 to keep up with the allocation rate? I'm ok >> taking some throughput hit to mitigate 90s+ pauses. >> >> The entire log might give a better picture. Especially if the marking >> cycle is triggered, how well the mixed gc cleans up the heap. >> >> _______________________________________________ >> hotspot-gc-use mailing list >> hotspot-gc-use@openjdk.java.net >> http://mail.openjdk.java.net/mailman/listinfo/hotspot-gc-use >> >> >> >> _______________________________________________ >> hotspot-gc-use mailing list >> hotspot-gc-use@openjdk.java.net >> http://mail.openjdk.java.net/mailman/listinfo/hotspot-gc-use >> >> > >
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