blocks|key|343664|text|g1将堆划分为几个区域，其中年轻代和老代各由几个区域组成。一个年轻的GC收集一些区域(并非全部)，然而，所有这些区域都被分配给年轻一代。混合GC收集一些区域(并非全部)，有些属于年轻一代，至少有一个属于老一代。一个完整的GC收集所有地区，因此，年轻一代和老一代。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|343665|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

The g1 divides the heap into regions, where the young generation and the old generation consists of several regions each.
A young GC collects some regions (not all), however, all of them are assigned to the young generation. A mixed GC collects some regions (not all), some belong the young generation, at least one to the old generation. A full GC collects all regions, and, in consequence, the young and the old generation.

blocks|key|2371251|text|在正常情况下，G1应该只运行年轻且混合的集合，以满足其暂停时间目标。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2371252|全面的全球合作是一种后备机制，很可能违反这些目标。当混合GC无法跟上分配时，当大量分配无法满足时，或者当System.gc()和其他一些条件要求GC时，就会出现这种情况。|offset|length|style|CODE|2371253|使用-XX:%2BPrintGCDetails进行日志记录应该包括一个完整集合的原因。|2371254|entityMap^0|0|1G|B|0|2|J|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|M|8|@$D|N|E|O|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|P|8|@$D|Q|E|R|F|G]]|9|@]|A|$]]|$1|J|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|K|$]]

Under normal conditions G1 should only run young and mixed collections to meet its pause time goals.

Full GCs are a fallback mechanism and likely to violate those goals. They occur when mixed GCs aren't able to keep up with allocations, when a humongous allocation could not be satisifed or when a GC is requested with <code>System.gc()</code> and some other conditions.

Logging with <code>-XX:+PrintGCDetails</code> should include a cause for full collections.

blocks|key|343801|text|来自甲骨文G1+GC博客和技术网络文章|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|343802|Young+GC:|style|BOLD|343803|青年GC的集合集仅包括年轻/幸存者区域。|343804|混合GC:|343805|混合GC的集合集既包括年轻/存活区域，也包括老区域。|343806|巨大的物体和巨大的分配|343807|For+G1+GC，任何超过半个区域大小的对象都被认为是“巨型对象”。这样的对象在老一代中直接分配到“大型区域s”中。这些巨大的区域是一组毗连的区域。|343808|在清除阶段的标记周期结束时，以及在一个完整的垃圾收集周期期间，死对象被释放为。|343809|为了减少复制开销，大型物体不包括在任何疏散暂停.一个完整的垃圾收集周期将大量的对象压缩到位。|343810|通常，一个完整的+GC会清理整个堆-，包括年轻空间和终身空间()。|343811|另外，您必须担心“应用程序线程被停止”的时间，而不管GC类型如何:年轻的GC或完整的GC等等。|343812|entityMap|0|LINK|mutability|MUTABLE|url|https://blogs.oracle.com/g1gc/entry/g1_gc_glossary_of_terms|1|http://www.oracle.com/technetwork/articles/java/g1gc-1984535.html^0|5|7|0|D|6|1|0|0|9|0|0|0|5|0|0|0|0|9|T|4|1F|4|0|V|7|0|0|8|3|I|D|0|0^^$0|@$1|2|3|4|5|6|7|19|8|@]|9|@$A|1A|B|1B|1|1C]|$A|1D|B|1E|1|1F]]|C|$]]|$1|D|3|E|5|6|7|1G|8|@$A|1H|B|1I|F|G]]|9|@]|C|$]]|$1|H|3|I|5|6|7|1J|8|@]|9|@]|C|$]]|$1|J|3|K|5|6|7|1K|8|@$A|1L|B|1M|F|G]]|9|@]|C|$]]|$1|L|3|M|5|6|7|1N|8|@]|9|@]|C|$]]|$1|N|3|O|5|6|7|1O|8|@]|9|@]|C|$]]|$1|P|3|Q|5|6|7|1P|8|@$A|1Q|B|1R|F|G]|$A|1S|B|1T|F|G]|$A|1U|B|1V|F|G]]|9|@]|C|$]]|$1|R|3|S|5|6|7|1W|8|@$A|1X|B|1Y|F|G]]|9|@]|C|$]]|$1|T|3|U|5|6|7|1Z|8|@]|9|@]|C|$]]|$1|V|3|W|5|6|7|20|8|@$A|21|B|22|F|G]|$A|23|B|24|F|G]]|9|@]|C|$]]|$1|X|3|Y|5|6|7|25|8|@]|9|@]|C|$]]|$1|Z|3|-4|5|6|7|26|8|@]|9|@]|C|$]]]|10|$11|$5|12|13|14|C|$15|16]]|17|$5|12|13|14|C|$15|18]]]]

From Oracle <a href="https://blogs.oracle.com/g1gc/entry/g1_gc_glossary_of_terms" rel="nofollow">G1 GC blog</a> and <a href="http://www.oracle.com/technetwork/articles/java/g1gc-1984535.html" rel="nofollow">technetwork article</a>

Young GC:

The collection set of the Young GC includes only young/survivor regions.

Mixed GC:

The collection set of the Mixed GC includes both young/survivor regions, but also old regions.

Humongous Objects and Humongous Allocations

For G1 GC, any object that is more than half a region size is considered a "Humongous object". Such an object is allocated directly in the old generation into "Humongous regions". These Humongous regions are a contiguous set of regions.

Dead Humongous objects are freed at the end of the marking cycle during the cleanup phase also during a full garbage collection cycle.

In-order to reduce copying overhead, the Humongous objects are not included in any evacuation pause. A full garbage collection cycle compacts Humongous objects in place.

Generally a Full GC cleans the entire Heap – both Young and Tenured spaces (old gen)

On a different note, you have to worry about how much time "application threads were stopped" irrespective of GC type : Young GC or Full GC etc.

blocks|key|199402|text|青年和混合GC之间的区别是：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|199403|混合GC包含旧区域填海(默认为旧区域的1/8)。|unordered-list-item|199404|当到达IHOP时将触发混合GC。(默认情况下，当旧世代>45%25时。)|199405|来自Oracle：https://docs.oracle.com/en/java/javase/11/gctuning/garbage-first-g1-garbage-collector1.html|offset|length|199406|Adaptive尝试设置初始堆占用，以便当旧代占用在当前最大旧代大小减去-XX:G1HeapReservePercent作为额外缓冲区的值时开始空间回收阶段的第一次混合垃圾收集。|blockquote|199407|对于完整的GC来说，|199408|在空间回收之后，收集周期又重新开始了另一个年轻阶段。作为备份，如果应用程序在收集活性信息时内存不足，G1将像其他收集器一样执行就地停止世界全堆压缩(Full+GC)。出现完整GC的原因是，应用程序分配了太多无法快速回收的对象。通常情况下，同时标记无法及时完成，以启动一个空间回收阶段.|199409|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.oracle.com/en/java/javase/11/gctuning/garbage-first-g1-garbage-collector1.html^0|0|0|0|9|2J|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Z|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|10|8|@]|9|@]|A|$]]|$1|E|3|F|5|D|7|11|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|12|8|@]|9|@$I|13|J|14|1|15]]|A|$]]|$1|K|3|L|5|M|7|16|8|@]|9|@]|A|$]]|$1|N|3|O|5|6|7|17|8|@]|9|@]|A|$]]|$1|P|3|Q|5|M|7|18|8|@]|9|@]|A|$]]|$1|R|3|-4|5|6|7|19|8|@]|9|@]|A|$]]]|S|$T|$5|U|V|W|A|$X|Y]]]]

The difference between young and mixed GC is:
<ul>
<li>Mixed GC contains the old regions reclamation (1/8 of old regions by default.)</li>
<li>Mixed GC will be triggered when IHOP is reached. (By default when the old gen &gt; 45%.)</li>
</ul>
From Oracle documentation:
<a href="https://docs.oracle.com/en/java/javase/11/gctuning/garbage-first-g1-garbage-collector1.html" rel="nofollow noreferrer">https://docs.oracle.com/en/java/javase/11/gctuning/garbage-first-g1-garbage-collector1.html</a>
<blockquote>
Adaptive IHOP tries to set the Initiating Heap Occupancy so that the first mixed garbage collection of the space-reclamation phase starts when the old generation occupancy is at a current maximum old generation size minus the value of -XX:G1HeapReservePercent as the extra buffer.
</blockquote>
For full GC,
<blockquote>
After space-reclamation, the collection cycle restarts with another young-only phase. As backup, if the application runs out of memory while gathering liveness information, G1 performs an in-place stop-the-world full heap compaction (Full GC) like other collectors.
</blockquote>
<blockquote>
The reason that a Full GC occurs is because the application allocates too many objects that can't be reclaimed quickly enough. Often concurrent marking has not been able to complete in time to start a space-reclamation phase.
</blockquote>

For garbage first collector, young gc means performing gc in young generation only and mixed gc would clean both young and old generation.

So what is full gc? Why it lasts longer than mixed gc?

I've done some searching but I didn't find any post that explains full gc.

G1: What are the differences between mixed gc and full gc?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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对于垃圾第一收集器，young gc意味着只在年轻一代中执行gc，而混合gc将同时清洗年轻一代和老一代。那么，什么是完全gc？为什么它比混合gc更长？我做了一些搜索，但没有找到任何解释全文gc的帖子。

问G1:混合gc和全gc有什么区别？
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问G1:混合gc和全gc有什么区别？
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