Hi Vitaly, Just to clarify things in case there might be some confusion … one of the terms in G1 can be a little confusing with a term used in Parallel GC, Serial GC and CMS GC, and that is “to-space”. In the latter case, “to-space” is a survivor space. In G1, “to-space” is any space that a G1 is evacuating objects too. So a “to-space exhausted” means that during an evacuation of live objects from a G1 region (which could be an eden region, survivor region or old region), and there is not an available region to evacuate those live objects, this constitutes a “to-space failure”.
I may be wrong, but my understanding is that once a humongous object is allocated, it is not evacuated. It stays in the same allocated region(s) until it is marked as being unreachable and can be reclaimed. charlie > On Oct 7, 2016, at 11:00 AM, Vitaly Davidovich <vita...@gmail.com> wrote: > > Hi Jenny, > > On Fri, Oct 7, 2016 at 11:52 AM, yu.zh...@oracle.com > <mailto:yu.zh...@oracle.com> <yu.zh...@oracle.com > <mailto:yu.zh...@oracle.com>> wrote: > Prasanna, > > In addition to what Vitaly said, I have some comments about your question: > > 1) Humongus allocation request for 72 mb failed, from the logs we can > also see we have free space of around 3 GB. Does this means , our > application is encountering high amount of fragmentation ?. > > It is possible. What it means is g1 can not find 36 consecutive regions for > that 72 mb object. > I agree the ReservePercent=40 is too high, but that should not prevent > allocating to the old gen. G1 tries to honor ReservePercent. > > So just to clarify - is the space (i.e. regions) reserved by G1ReservePercent > allocatable to humongous object allocations? All docs/webpages I found talk > about this space being for holding survivors (i.e. evac failure/to-space > exhaustion mitigation). It sounds like you're saying these reserved regions > should also be used to satisfy HO allocs? > > Thanks > _______________________________________________ > 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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