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 Changes requested by franz1...@github.com (no known OpenJDK username). src/java.base/share/classes/jdk/internal/foreign/AbstractMemorySegmentImpl.java line 208: > 206: } > 207: final long u = Byte.toUnsignedLong(value); > 208: final long longValue = u << 56 | u << 48 | u << 40 | u << 32 > | u << 24 | u << 16 | u << 8 | u; this can be u * 0xFFFFFFFFFFFFL if value != 0 and just 0L if not: not sure if fast(er), need to measure. Most of the time filling is happy with 0 since zeroing is the most common case ------------- PR Review: https://git.openjdk.org/jdk/pull/20712#pullrequestreview-2272430113 PR Review Comment: https://git.openjdk.org/jdk/pull/20712#discussion_r1738721722
