Ankur
e189da79ba
Complete companion suite for the ankurm.com guide. Everything was compiled and
executed on java 25.0.3+9-LTS-195 (AMD Ryzen 5 5600U, Windows 11); every file
under results/ is unedited program output.
Code
latency/ open-loop latency harness that measures from intended arrival, so
coordinated omission is accounted for rather than hidden. Reports
response time and service time side by side; the gap reached 2910x
on G1.
jmh/ four microbenchmarks isolating one mechanism each: TLAB allocation,
the ZGC load barrier (with a primitive-load control), the write
barrier (with null / old-to-old / primitive controls), and promotion
pressure.
tuning/ provokes ZGC allocation stalls and reads its own JFR recording back,
grouped by page class. jdk.ZAllocationStall is enabled without a
threshold, because the 10 ms default hides most stalls.
internals/ ZGC page classes vs G1 humongous, read from the live VM via
HotSpotDiagnosticMXBean and jdk.ZPageAllocation events.
analysis/ unified GC log parser that keeps stop-the-world pauses and
concurrent phases in separate buckets.
env/ environment capture; proves generational mode from JMX bean names.
Docs
Eight chapters covering the JEP 439/474/490 timeline, colored pointers and both
barriers, allocation stalls, a full flag reference, logging and JFR, benchmark
methodology, corner cases, and a decision procedure.
Headline result (60 s, 20k req/s, 2 GB heap, ~585 MB live)
p50 ZGC 0.006 ms G1 0.005 ms
p99.9 ZGC 1.437 ms G1 95.169 ms
total STW time ZGC 1.503 ms G1 1,139.624 ms
48 lines
1.9 KiB
Plaintext
48 lines
1.9 KiB
Plaintext
==============================================================================
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ZGC / G1 open-loop latency harness
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==============================================================================
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collector : G1 Young Generation + G1 Concurrent GC + G1 Old Generation
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java : 25.0.3+9-LTS-195
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threads=4 rate=20,000/s warmup=20s measure=60s
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liveSet=150,000 entries x 4,096 B (~585 MB live)
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garbage=16,384 B/request reads=64/request mutationProbability=0.20
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nominal allocation rate ~328 MB/s seed=20260730
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------------------------------------------------------------------------------
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building live set ... 150,000 entries, ~589 MB live, took 266 ms
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warming up for 20 s at 20,000 req/s ...
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measuring for 60 s at 20,000 req/s ...
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------------------------------------------------------------------------------
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achieved throughput : 19,976 req/s over 60.1 s
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RESPONSE TIME (from intended arrival -- the honest number) (n=1,200,000)
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mean 0.388 ms
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p50 0.005 ms
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p90 0.009 ms
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p99 8.042 ms
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p99.9 95.169 ms
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p99.99 126.949 ms
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max 133.018 ms
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SERVICE TIME (from actual start -- hides queueing) (n=1,200,000)
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mean 0.007 ms
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p50 0.005 ms
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p90 0.008 ms
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p99 0.016 ms
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p99.9 0.033 ms
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p99.99 0.171 ms
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max 113.864 ms
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coordinated-omission gap at p99.9 : 95.169 ms response vs 0.033 ms service (2910.4x)
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GC activity during the measured window
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G1 Young Generation collections=36 time= 604 ms [stop-the-world]
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G1 Concurrent GC collections=19 time= 15 ms [cycle (mostly concurrent)]
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G1 Old Generation collections=2 time= 208 ms [stop-the-world]
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CSV (response time)
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collector,n,mean_ms,p50_ms,p90_ms,p99_ms,p999_ms,p9999_ms,max_ms
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G1 Young Generation + G1 Concurrent GC + G1 Old Generation,1200000,0.388,0.005,0.009,8.042,95.169,126.949,133.018
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liveSet checksum: 0
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