On Wed, 19 Nov 2025 13:29:28 GMT, Harald Eilertsen <[email protected]> wrote:
>> `jdk.internal.foreign.SegmentFactories::allocateNativeInternal` assumes that >> the underlying implementation of malloc aligns allocations on 16 byte >> boundaries for 64 bit platforms, and 8 byte boundaries on 32 bit platforms. >> So for any allocation where the requested alignment is less than or equal to >> this default alignment it makes no adjustment. >> >> However, this assumption does not hold for all allocators. Specifically >> jemallc, used by libc on FreeBSD will align small allocations on 8 or 4 byte >> boundaries, respectively. This causes allocateNativeInternal to sometimes >> return memory that is not properly aligned when the requested alignment is >> exactly 16 bytes. >> >> To make sure we honour the requested alignment when it exaclty matches the >> quantum as defined by MAX_MALLOC_ALIGN, this patch ensures that we adjust >> the alignment also in this case. >> >> This should make no difference for platforms where malloc allready aligns on >> the quantum, except for a few unnecessary trivial calculations. >> >> This work was sponsored by: The FreeBSD Foundation > > Harald Eilertsen has updated the pull request incrementally with one > additional commit since the last revision: > > Replace conditional with Math.max intrinsic > > Co-authored-by: ExE Boss <[email protected]> src/java.base/share/classes/jdk/internal/foreign/SegmentFactories.java line 215: > 213: result = Utils.alignUp(allocationBase, byteAlignment); > 214: } else { > 215: allocationSize = Math.max(alignedSize, byteAlignment); This looks correct but it really needs a comment. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/28235#discussion_r2546407970
