1. The document reports on progress of a swap-aware JVM garbage collector that allows free space between live objects using dummy objects. 2. It describes the multi-threaded marking, compacting, and post-compacting phases of the GC and a problem with dense object prefixes becoming unavailable. 3. Benchmark results are shown for the SPECjvm2008 benchmark suite run with the GC, reporting swap I/O and GC times for various workloads.

1. Hyojeong Lee
Distributed Computing System Laboratory
Department of Computer Science and Engineering
Seoul National University, Korea
Progress Report

2. Swap-aware JVM GC
● Scheme: Skip source-destination mapping
● Validation: with microbench

3. ● Debugging
● Evaluation w/ SPECjvm2008 benchmark
● Kernel API
DOING

4. ● Problem: Current GC doesn’t allow free space between live objects.
● Solution: Dummy object (ref. scissorGC at VEE’19)
→ Remaining problem:
Swap-aware JVM GC: debugging
Marking (multi-thr) → Summary (single-thr)
- mark_live_object (to bitmap)
- check_skippable_region
- fill_and_mark_holes_with_dummy
- map_src_dest (skip swapped region’s mapping)
Compact (multi-thr)
- update_object_ptr (ptr of skippable region will be
updated to itself)
- object is unmarked
- dense_prefix_task (update dense prefix)
- dense_prefix is unavailable (dead object)
Post-compact (multi-thr)
- verify_ptrs (check all object ptr is available)
SPECjvm2008
● derby
● scimark.fft.large
● serial
● crypto.aes
● xml.validation
● sunflow
● mpegaudio
● compress

5. ● Benchmark (heap/memory in MB) → Swap I/O & GC time
● derby (600/200)
● scimark.fft.large (650/200)
● serial (200/100)
● crypto.aes (500/200)
● xml.validation (200/100)
SPECjvm2008 benchmark
Configuration
mode timed run
runtime (s) 120
GC thread 8
iteration 5
Module overhead
scan time (s) ~ 2
ops/m

6. ● derby
- Swap I/O - GC time (avg of 2 times)
SPECjvm2008 benchmark
swapout (byte)
swapin (byte)
13.5
17.8
TODO
- more metric
: throughput (ops/m → ops/s)
- other workloads
0 12060 9030
0 12060 9030
15 45 75 105
15 45 75 105
1st FGC

7. ● 커널 API 구현
Swap-aware JVM GC: 모듈 최적화
fs/proc/task_mmu.c

8. ● Debugging + Evaluation (~ 4.26)
● 커널 API 구현 (~ 4.15)
TODO