On Wed, 31 Jan 2024 21:12:19 GMT, Dmitry Chuyko <dchu...@openjdk.org> wrote:
>> Compiler Control (https://openjdk.org/jeps/165) provides method-context >> dependent control of the JVM compilers (C1 and C2). The active directive >> stack is built from the directive files passed with the >> `-XX:CompilerDirectivesFile` diagnostic command-line option and the >> Compiler.add_directives diagnostic command. It is also possible to clear all >> directives or remove the top from the stack. >> >> A matching directive will be applied at method compilation time when such >> compilation is started. If directives are added or changed, but compilation >> does not start, then the state of compiled methods doesn't correspond to the >> rules. This is not an error, and it happens in long running applications >> when directives are added or removed after compilation of methods that could >> be matched. For example, the user decides that C2 compilation needs to be >> disabled for some method due to a compiler bug, issues such a directive but >> this does not affect the application behavior. In such case, the target >> application needs to be restarted, and such an operation can have high costs >> and risks. Another goal is testing/debugging compilers. >> >> It would be convenient to optionally reconcile at least existing matching >> nmethods to the current stack of compiler directives (so bypass inlined >> methods). >> >> Natural way to eliminate the discrepancy between the result of compilation >> and the broken rule is to discard the compilation result, i.e. >> deoptimization. Prior to that we can try to re-compile the method letting >> compile broker to perform it taking new directives stack into account. >> Re-compilation helps to prevent hot methods from execution in the >> interpreter. >> >> A new flag `-r` has beed introduced for some directives related to compile >> commands: `Compiler.add_directives`, `Compiler.remove_directives`, >> `Compiler.clear_directives`. The default behavior has not changed (no flag). >> If the new flag is present, the command scans already compiled methods and >> puts methods that have any active non-default matching compiler directives >> to re-compilation if possible, otherwise marks them for deoptimization. >> There is currently no distinction which directives are found. In particular, >> this means that if there are rules for inlining into some method, it will be >> refreshed. On the other hand, if there are rules for a method and it was >> inlined, top-level methods won't be refreshed, but this can be achieved by >> having rules for them. >> >> In addition, a new diagnostic command `Compiler.replace_directives... > > Dmitry Chuyko has updated the pull request with a new target base due to a > merge or a rebase. The pull request now contains 43 commits: > > - Merge branch 'openjdk:master' into compiler-directives-force-update > - Merge branch 'openjdk:master' into compiler-directives-force-update > - Merge branch 'openjdk:master' into compiler-directives-force-update > - Merge branch 'openjdk:master' into compiler-directives-force-update > - Merge branch 'openjdk:master' into compiler-directives-force-update > - Merge branch 'openjdk:master' into compiler-directives-force-update > - Deopt osr, cleanups > - Merge branch 'openjdk:master' into compiler-directives-force-update > - Merge branch 'openjdk:master' into compiler-directives-force-update > - Merge branch 'openjdk:master' into compiler-directives-force-update > - ... and 33 more: https://git.openjdk.org/jdk/compare/5b9b176c...ea0322cd @sspitsyn Can I please have someone from serviceability group take a look at this? Comments from Paul and Andrei have been addressed a while ago. ------------- PR Comment: https://git.openjdk.org/jdk/pull/14111#issuecomment-1942717023
