RFR: 8356027: Print enhanced compilation timings [v4]
Aleksey Shipilev
shade at openjdk.org
Mon May 5 16:37:00 UTC 2025
> In Leyden, we have the extended compilation timings printouts with -XX:+PrintCompilation / UL, that are very useful to study compiler dynamics. These timings include:
> 1. Time spent before queuing: shows the compilation queue bottlenecks
> 2. Time spent in the queue: shows delays caused by queue bottlenecks and compiler load
> 3. Time spent actually compiling: shows the per-method compilation costs
>
> We should consider the same kind of printout for mainline. This would also require us to print the compilation task _after_ the compilation, not only before it. This improvement would also obviate any need for `PrintCompilation2` flag, [JDK-8356028](https://bugs.openjdk.org/browse/JDK-8356028).
>
> The difference from the output format we ship in Leyden:
> 1. This output prints before/after the compilation to maintain old behavior partially. The "before" printout is now prepended with `started` to clearly mark it as such.
> 2. The output is raw number in microseconds. In Leyden repo, we have these prepended with characters, like `C0.1`, but that prepending makes it a bit inconvenient with scripts. This PR also does microseconds, instead of fractional milliseconds. This should be enough to capture the wide range of durations.
>
> See the sample `-XX:+PrintCompilation` output in the comments.
>
> Additional testing:
> - [x] Linux x86_64 server fastdebug, `compiler`
> - [x] Linux x86_64 server fastdebug, `all`
Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:
Revert the shared printing block
-------------
Changes:
- all: https://git.openjdk.org/jdk/pull/24984/files
- new: https://git.openjdk.org/jdk/pull/24984/files/4eb0dde9..750ac377
Webrevs:
- full: https://webrevs.openjdk.org/?repo=jdk&pr=24984&range=03
- incr: https://webrevs.openjdk.org/?repo=jdk&pr=24984&range=02-03
Stats: 32 lines in 1 file changed: 8 ins; 3 del; 21 mod
Patch: https://git.openjdk.org/jdk/pull/24984.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/24984/head:pull/24984
PR: https://git.openjdk.org/jdk/pull/24984
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