Thanks Thomas, do you know if there is overhead of those flags? I think trace would be expensive but what about others? Will they add anything to pause time?
On Wed, Feb 8, 2017 at 9:01 PM, Thomas Schatzl <thomas.scha...@oracle.com> wrote: > Hi, > > On Tue, 2017-02-07 at 19:06 +0530, Amit Balode wrote: > > Any thoughts on how we could find how much space is fragmented in G1 > > regions? > > -XX:+G1PrintRegionLivenessInfo prints region information containing > its type after every marking (use gc+liveness=trace for jdk9) twice. > The first "post-marking" output is what you want. The "post-sorting" > one is only interesting for getting details about the collection set > (and this one does not contain free regions). > > The first column contains information about the type of the region: > > FREE -> free region > SURV -> survivor region > EDEN -> eden region > HUMS -> humongous (start) > HUMC -> humongous (continuation) > OLD -> old region > ARC -> archive regions (jdk9 only I think, not sure, maybe also jdk8) > > From that you can deduce the size and how many contiguous free regions > are available at the moment. > > There is also -XX:+PrintHeapAtGC and -XX:+PrintHeapAtGCExtended which > print the region layout at every GC. > > Thanks, > Thomas > > -- Thanks & Regards, Amit.Balode
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