11 * [GC](#gc)
25   - some baseline GC with profile-based configuration(if available)
28 …- low-pause/pauseless GC(for games) or GC with high throughput and acceptable STW pause (for not g…
64 * Marked for GC or not
77 |               nothing:61          | GC:1 | state:00 |     OOP to metadata object     |       Unlo…
79 |    tId:29    |      Lcount:32     | GC:1 | state:00 |     OOP to metadata object     |  Lightweig…
81 |               Monitor:61          | GC:1 | state:01 |     OOP to metadata object     |  Heavyweig…
83 |                Hash:61            | GC:1 | state:10 |     OOP to metadata object     |       Hash…
85 |           Forwarding address:62          | state:11 |     OOP to metadata object     |         GC…
95 |               nothing:29          | GC:1 | state:00 |     OOP to metadata object     |       Unlo…
97 |    tId:13    |      Lcount:16     | GC:1 | state:00 |     OOP to metadata object     |  Lightweig…
99 |               Monitor:29          | GC:1 | state:01 |     OOP to metadata object     |  Heavyweig…
101 |                Hash:29            | GC:1 | state:10 |     OOP to metadata object     |       Hash…
103 |           Forwarding address:30          | state:11 |     OOP to metadata object     |         GC…
114 |        nothing:28        | Hash:1 | GC:1 | state:00 |     OOP to metadata object     |       Unlo…
116 |  tId:13  |   LCount:15   | Hash:1 | GC:1 | state:00 |     OOP to metadata object     |  Lightweig…
118 |        Monitor:28        | Hash:1 | GC:1 | state:01 |     OOP to metadata object     |  Heavyweig…
120 |   Forwarding address:28  | Hash:1 | GC:1 | state:11 |     OOP to metadata object     |         GC…
124 …t requires extra memory after GC moved the object (where the original hash value will be stored) a…
125 But, this scenario will be useful if we have allocator and GC which decreases such a situation to a…
134 |               nothing:13          | GC:1 | state:00 |     OOP to metadata object     |       Unlo…
136 |    thread Id:7    | Lock Count:6  | GC:1 | state:00 |     OOP to metadata object     |  Lightweig…
138 |               Monitor:13          | GC:1 | state:01 |     OOP to metadata object     |  Heavyweig…
140 |                Hash:13            | GC:1 | state:10 |     OOP to metadata object     |       Hash…
142 |         Forwarding address:14            | state:11 |     OOP to metadata object     |         GC…
156 GC - the object has been moved by GC. 
207 | String Hash | GC bit (1 bit) | Status (2 bits) |    <--- Mark Word (32 bits)
316 …ve some preallocated buffer which allow Runtime to continue to work, while GC trying to free memor…
329   - Internal memory space for non-compiler part of runtime (including GC internals)
340 Logical GC spaces:
345 ## GC  section in Memory management and object layout. Design.
347 Garbage collector(GC) automatically recycles memory that it can prove will never be used again.
349 GC development will be iterative process.
352 - precise GC (see [glossary](./glossary.md#memory-management-terms))
353 - GC should support various [modes](#overview)(performance, power-saving mode, normal mode);
354 - GC suitable for each mode he shouldn't violate requirements for this mode(see [here](#overview))
358 - GC barriers support by Interpreter and JIT
362 So we should have possibility to use optimal GC for each application.
364 ### Epsilon GC  argument
366 Epsilon GC does absolutely nothing but makes the impression that Runtime has GC. I.e., it supports …
368 Epsilon GC should be used only for debug and profiling purposes. I.e., we can disable GC and measur…
370 ### STW GC  argument
372 Stop-The-World GC.
374 Non-generational non-moving GC, during the work all mutator threads should be at safepoint.
380 ### Concurrent Mark Sweep GC   argument
390 - generational moving (optionally compacting) GC
391 - (optional) generational non-moving (optionally compacting) GC
402 Since one of the metric for this GC - high throughput, the most of the objects in the Eden will liv…
406 Minor GC(STW):
411 Note: we'll use adaptive thresholds for triggering Minor GC for minimizing STW pause
412 Note #2: we can tune minor GC by trying make concurrent marking and re-mark, but it will require co…
414 Major GC
424 Note: If we don't have Survivor spaces we can implement non-moving generational GC. 
426 ### Region based GC (main)  argument
434 Since typical heap size for mobile applications is small - this GC can be considered as good choice…
454 Minor GC(only for young regions - STW):
461 Mixed GC - minor GC + some tenured regions added to the young gen regions after the concurrent mark…
470 ### Low-pause GC (deffered)  argument
477 No explicit minor GC.
479 Major GC
486 …with big heap or for applications when it is hard to provide stable low pause with Region based GC.
491 ### GC: interaction with Interpreter, JIT and AOT  argument
511 When GC wants to stop the world, it forces it by stopping all threads at the safepoint.
516 For each safepoint, we should have a method that can provide GC with information about objects on t…
538 #### GC Barriers
540 GC barrier is a block on writing to(write barrier) or reading from(read barrier) certain memory by …
542 ##### GC Write Barriers
544 Heap inconsistency can happen when GC reclaim alive/reachable object.
551 So we can solve these issues with GC WRB(write barrier). GC WRB can be _pre_(inserted before the st…
574 ##### GC Read Barriers
583 #### GC Barriers integration with Interpreter and compiler
596 …d could provide some more compiler-friendly interface to the other compilers to encode GC barriers.