On Fri, 22 Dec 2023 13:53:42 GMT, Vladimir Sitnikov <vsitni...@openjdk.org> wrote:
>> test/jdk/java/io/BufferedInputStream/TransferToTrusted.java line 68: >> >>> 66: >>> 67: var bis = new BufferedInputStream(new >>> ByteArrayInputStream(dup)); >>> 68: bis.mark(dup.length); >> >> If you take a closer look into `BIS::transferTo()` then you will notice that >> in case you call `bis.mark()` then your optimization will effectively *not >> getting called at all*, due to this line: >> https://github.com/openjdk/jdk/pull/16879/files#diff-e19c508d1bb6ee78697ecca66947c395adda0d9c49a85bf696e677ecbd977af1L643. >> So Brian's comment still applies and you should fix your test before this >> PR can be accepted for a merge (hence: you MUST get rid of `mark()`). > > Can anybody give a hint how one can create assertions in OpenJDK test code > that would check the amount of allocated heap for the tested method? > > Since the change here is "removal of an allocation", the assert in the code > should probably allow only a very small allocation in `.transferTo`. > > Does `com.sun.management.ThreadMXBean#getCurrentThreadAllocatedBytes()` sound > right for the test? I think there is a misundertanding. This PR is not intendend to reduce the *amount* of allocated heap, it is about sparing time by not creating *temporary copies*. The latter should be rather easy to check: Invoke `transferTo(out)` two times in a row and compare the *identity* of the two byte arrays passed to `out.write()`. If they stay the same, then apparently no *temporary copy* was created. Two achieve this, the BIS must be wrapper around an extendable input stream (like `FileInputStream`) so between calls the stream could get extended (e. g. by writing into the file). ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/16879#discussion_r1435108416
