On Fri, 30 Aug 2024 10:51:59 GMT, Per Minborg <pminb...@openjdk.org> wrote:
>> The performance of the `MemorySegment::fil` can be improved by replacing the >> `checkAccess()` method call with calling `checkReadOnly()` instead (as the >> bounds of the segment itself do not need to be checked). >> >> Also, smaller segments can be handled directly by Java code rather than >> transitioning to native code. >> >> Here is how the `MemorySegment::fill` performance is improved by this PR: >> >>  >> >> Operations involving 8 or more bytes are delegated to native code whereas >> smaller segments are handled via a switch rake. >> >> It should be noted that `Arena::allocate` is using `MemorySegment::fil`. >> Hence, this PR will also have a positive effect on memory allocation >> performance. > > Per Minborg has updated the pull request incrementally with two additional > commits since the last revision: > > - Revert copyright year > - Move logic back to AMSI src/java.base/share/classes/jdk/internal/foreign/AbstractMemorySegmentImpl.java line 200: > 198: checkReadOnly(false); > 199: // 0...0X...XXXX implies: 0 <= length < FILL_NATIVE_LIMIT > 200: if ((length & -FILL_NATIVE_THRESHOLD) == 0) { Looks great - few notes: * adding `@ForceInline` here might help * I'd suggest to move the `length == 0` outside in its own `if` branch (and drop the `return` from there). E.g. if (length == 0) { ... } else if (length & -FILL...) { ... } else { ... } return this; ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/20712#discussion_r1738755601
