Summary: G1ElasticHeap to support heap shrink/expansion in runtime

Test Plan:
test/elastic-heap/

Reviewers:

Issue:
https://github.com/alibaba/dragonwell8/issues/46

CR:
https://github.com/alibaba/dragonwell8_hotspot/pull/12

Test Plan: existing test cases

Reviewed-by: shiyue, kuaiwei

Issue: https://github.com/alibaba/dragonwell8/issues/52

Summary:
- Port fix D2553 to Dragonwell
- Change default GC policy to UseConcMarkSweepGC

Test Plan: hotspot/test/gc/TestDefaultGC.sh

Reviewers: 井桐

Reviewed By: 井桐

Subscribers:

Differential Revision: https://aone.alibaba-inc.com/code/D849276

Reviewers: 效山, 芳玺, 传胜, 三红, yumin.qi

Reviewed By: 三红, 芳玺, 效山, 卓仁

Differential Revision: https://aone.alibaba-inc.com/code/D815657

Summary: Summary: os::readdir uses POSIX readdir, drop buffer arg, fix JFR uses.
Reviewed-by: coleenp, tschatzl, bsrbnd, shade, phh

Reviewed-by: erikj, dholmes

Reviewed-by: tschatzl

Reviewed-by: bobv, dbuck

Reviewed-by: bobv, dbuck

Summary: Set UseLoopCounter ergonomically if on-stack-replacement is enabled. Print warning.
Reviewed-by: kvn

Reviewed-by: kvn, dholmes, bobv

Reviewed-by: kvn, dholmes, bobv

Reviewed-by: kbarrett, stefank

Reviewed-by: kbarrett, stefank

8170888: [linux] Experimental support for cgroup memory limits in container (ie Docker) environments
Summary: Set apparent physical memory to cgroup memory limit when UseCGroupMemoryLimitForHeap is true
Reviewed-by: acorn, gtriantafill
Contributed-by: NChristine Flood <chf@redhat.com>

8170888: [linux] Experimental support for cgroup memory limits in container (ie Docker) environments
Summary: Set apparent physical memory to cgroup memory limit when UseCGroupMemoryLimitForHeap is true
Reviewed-by: acorn, gtriantafill
Contributed-by: NChristine Flood <chf@redhat.com>

8170888: [linux] Experimental support for cgroup memory limits in container (ie Docker) environments
Summary: Set apparent physical memory to cgroup memory limit when UseCGroupMemoryLimitForHeap is true
Reviewed-by: acorn, gtriantafill
Contributed-by: NChristine Flood <chf@redhat.com>

Reviewed-by: gthornbr, hseigel, mschoene
Contributed-by: gerard.ziemski@oracle.com

Reviewed-by: iklam, hseigel, acorn, mschoene

Reviewed-by: jmasa, kbarrett, tschatzl

Summary: for fixing a truncation problem on the output from -XX:+TraceClassPaths
Reviewed-by: coleenp, jiangli, cjplummer, minqi

Summary: CMSClassUnloadingEnabled and ExplicitGCInvokesConcurrentAndUnloadsClasses should be disabled when -Xnoclassgc is specified
Reviewed-by: jmasa, kbarrett

Summary: CMSClassUnloadingEnabled and ExplicitGCInvokesConcurrentAndUnloadsClasses should be disabled when -Xnoclassgc is specified
Reviewed-by: jmasa, kbarrett

Reviewed-by: lfoltan, sspitsyn

Reviewed-by: kbarrett, dholmes

Reviewed-by: hseigel, ccheung

Summary: Added a G1CollectorPolicyExt where it is possible to extend the class.
Reviewed-by: sjohanss, tschatzl

Reviewed-by: coleenp, ccheung

Summary: Update the URL for HotSpot bug reports.
Reviewed-by: dcubed, rdurbin

Summary: Update the URL for HotSpot bug reports.
Reviewed-by: dcubed, rdurbin

Reviewed-by: jmasa, ahgross
Contributed-by: sangheon.kim@oracle.com

Summary: Ergonomics updates flags for number of GC threads
Reviewed-by: tschatzl, jwilhelm
Contributed-by: sangheon.kim@oracle.com

Reviewed-by: brutisso, mgerdin, tschatzl

Reviewed-by: mgerdin, tschatzl, jmasa

Summary: Re-enabled warning as launcher change reached promotion build
Reviewed-by: hseigel, coleenp

Summary: Add checksum verification.
Reviewed-by: iklam, dholmes, mschoene

Summary: Add checksum verification.
Reviewed-by: iklam, dholmes, mschoene

Summary: Cleaned up CDS to be more configurable, maintainable and extensible
Reviewed-by: dholmes, coleenp, acorn, mchung

Summary: Enhance scalability of native memory tracking
Reviewed-by: coleenp, ctornqvi, gtriantafill

Reviewed-by: brutisso, tschatzl