RFR: 8360783: CTW: Skip deoptimization between tiers [v2]
Tobias Hartmann
thartmann at openjdk.org
Tue Jul 1 07:47:40 UTC 2025
On Fri, 27 Jun 2025 08:38:31 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:
>> When profiling CTW runs, I noticed we spend a lot of time dealing with deoptimization. We do this excessively, deoptimizing before compilation on every tier. This is excessive: Hotspot honors compilation requests on subsequent levels without the need for explicit deoptimization. Not doing deopt between tiers greatly improves CTW performance.
>>
>> A taste of improvements, about 15% less CPU spent:
>>
>>
>> $ time make test TEST=applications/ctw/modules
>>
>> # Current
>> real 5m1.616s
>> user 79m41.398s
>> sys 14m39.607s
>>
>> # Patched
>> real 3m55.411s
>> user 69m19.227s
>> sys 5m24.323s
>>
>>
>> The compilation still works as expected, progressing through tiers 1..4:
>>
>>
>> $ JAVA_OPTIONS="-XX:+PrintCompilation -XX:CICompilerCount=2" ./ctw.sh modules:jdk.compiler | tee out
>> ...
>> $ grep sun.tools.serialver.resources.serialver_de::getContents out
>> 101783 55033 b 1 sun.tools.serialver.resources.serialver_de::getContents (108 bytes)
>> 101785 55036 b 2 sun.tools.serialver.resources.serialver_de::getContents (108 bytes)
>> 101786 55033 1 sun.tools.serialver.resources.serialver_de::getContents (108 bytes) made not entrant: not used
>> 101786 55038 b 3 sun.tools.serialver.resources.serialver_de::getContents (108 bytes)
>> 101787 55036 2 sun.tools.serialver.resources.serialver_de::getContents (108 bytes) made not entrant: not used
>> 101792 55040 b 4 sun.tools.serialver.resources.serialver_de::getContents (108 bytes)
>> 101797 55038 3 sun.tools.serialver.resources.serialver_de::getContents (108 bytes) made not entrant: not used
>> 101798 55040 4 sun.tools.serialver.resources.serialver_de::getContents (108 bytes) made not entrant: marked for deoptimization
>
> Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:
>
> Update test/hotspot/jtreg/testlibrary/ctw/src/sun/hotspot/tools/ctw/Compiler.java
>
> Co-authored-by: Tobias Hartmann <tobias.hartmann at oracle.com>
Marked as reviewed by thartmann (Reviewer).
-------------
PR Review: https://git.openjdk.org/jdk/pull/26013#pullrequestreview-2973981844
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