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
49 lines
2.0 KiB
Plaintext
49 lines
2.0 KiB
Plaintext
==============================================================================
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ZGC / G1 open-loop latency harness
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==============================================================================
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collector : ZGC Minor Cycles + ZGC Minor Pauses + ZGC Major Cycles + ZGC Major Pauses
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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 310 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 : 19,973 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 0.016 ms
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p50 0.006 ms
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p90 0.009 ms
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p99 0.029 ms
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p99.9 1.437 ms
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p99.99 23.675 ms
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max 32.178 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 0.006 ms
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p90 0.009 ms
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p99 0.025 ms
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p99.9 0.143 ms
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p99.99 0.269 ms
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max 8.353 ms
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coordinated-omission gap at p99.9 : 1.437 ms response vs 0.143 ms service (10.0x)
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GC activity during the measured window
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ZGC Minor Cycles collections=18 time= 919 ms [cycle (mostly concurrent)]
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ZGC Minor Pauses collections=54 time= 0 ms [stop-the-world]
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ZGC Major Cycles collections=3 time= 667 ms [cycle (mostly concurrent)]
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ZGC Major Pauses collections=15 time= 0 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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ZGC Minor Cycles + ZGC Minor Pauses + ZGC Major Cycles + ZGC Major Pauses,1200000,0.016,0.006,0.009,0.029,1.437,23.675,32.178
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liveSet checksum: 1
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