for example, is the JVM, of the generation collection algorithm GC used to divide the young and the old,
or no matter which GC algorithm is used, the heap is divided into the young and the old?
jvm standard has almost no specific requirements for GC
Java virtual machine specification does not give any definition of GC, nor does it classify the heap. Therefore, in theory, it is not certain whether to distinguish between the young and the old.
quote the words in "in-depth understanding of the Java virtual machine":
first of all, there is no provision in the Java virtual machine specification for how the garbage collector should be implemented.
current commercial virtual machine garbage collection uses "generational collection" (Generational Collection) algorithm, which has no new idea, but divides memory into several blocks according to the survival period of objects. Generally, the Java heap is divided into the new generation and the old age, so that the most appropriate collection algorithm can be adopted according to the characteristics of each age.however, no matter how the partition, it has nothing to do with the storage content, no matter which area, the storage is still the object instance, the purpose of further partition is to better reclaim memory, or to allocate memory faster.
that is to say, generational collection is the best solution found so far to better reclaim memory or allocate memory faster.
several GC introduced in it are all based on generational collection (including G1). For several garbage collection algorithms introduced (tag-clear, copy, tag-collate), they will be more efficient under generational collection.
see a paragraph: < H2 > before Minor GC occurs, the virtual machine checks whether the largest contiguous space available in the old era is larger than the total space of all objects in the new generation. If this condition is true, then Minor GC can e...
https: www.cnblogs.com ggjuc. this article says: < H2 > 1 CMS will not defragment the heap, so in order to prevent full gc, from causing heap fragmentation, merge the fragments by opening the CMS phase: < H2 > does this mean that after CMS full g...
in working memory, there are method stack frames and registers. Pc, is understandable, but why should some referenced main memory variables be copied to working memory? I don t think it s necessary at all, which leads to cache consistency problems. Or...
the program first executes a start method to take up a lot of memory, and then executes endEmpty to call System.gc () to run, the task manager can see that the memory footprint of the program immediately reaches 4G, but the memory footprint of th...
The code is as follows: package referenceCoutingGC; ** * * testGC()ogjAogjBGC * * public class referenceCoutingGC { public Object instance = null; private static final int _1MB = 1024*1024; private byte[] bigSize = ...
new method protected String constructScalar(ScalarNode node) { return node.getValue(); } old method protected Object constructScalar(ScalarNode node) { return node.getValue(); } in an old program, the retur...
what s the difference between CMSInitiatingOccupancyFraction and CMSTriggerRatio as the name implies, it feels like the same concept ...
the most common passage about CMSFullGCsBeforeCompaction, is: < hr > CMSFullGCsBeforeCompaction is talking about how many more times full GC has to be executed before compression has been done since the last CMS concurrent GC execution. The default is...
if you dump through a thread, you can only get information at a certain point in time (incomplete). But if you use JVM monitoring tool sampling, looking for a specific method after the implementation process is too troublesome, is there any other way? ...
as shown below, metaspace and CCS account for more than 90%. Does this have a great impact on the process? How to deal with it? $JAVA_HOME bin jstat-gcutil 27553 S0 S1 E OM CCS YGC YGCT FGC FGCT GCT 0.00 100.00 13.05 97.12 94.61 9 0.306 3 0.469 0.77...
is shown below: both the meta-space utilization M and the compressed space utilization CCS are above 95%. What does this mean? Is there a problem? the number of full gc is small, only a few times in many days [root@localhost eversec]-sharp cat temp ...
< H2 > description < H2 > physical environment 2GB memory < H2 > phenomenon description: < H2 > I have a program (no source code) that uses Netty at the bottom (don t be misled into a problem with NIO, but it may be related to DirectMemory), ther...
Why is there a sudden increase in hop time and no increase in YGC and FGC when using the jstat-gcutil monitor gc? S0 S1 E O M CCS YGC YGCT FGC FGCT GCT 40.57 0.00 0.00 96.12 94.08 91.92 254 59.554 ...