On Wed, 15 Jan 2025 09:48:33 +0000, Colin Paice <colinpai...@gmail.com> wrote:
>With the first start of z/OSMF, all of the (jar) files need to be read from >disk into ZFS cache. The restart of z/OSMF will benefit from the files >being in ZFS cache, and so the second time OSMF will start faster, and use >less CPU. That's only partially true if it's big enough. zFS cache is "most recently used". So if e.g. a liberty server with another Java version was started 2 or 3 times after zOSMF, there might not be much left in the cache. Furthermore zFS caches blocks, not files. So even if most of a file is in the cache, some blocks might have to be reloaded. Next flaw of zFS is, that there is no way to fix any frequently read files in the cache. SHRLIBRGN (is not zFS) can cache shared libraries (.so files) but is in 31bit and lowers 31bit private for all address spaces. In addition, a file with the same name can only be loaded once. So if libjvm.so from JDK 11 is there, libjvm.so from JDK 17 cannot be cached. When SHRLIBRGN is empty, it stores shared libraries as they are used by the system and they remain there. If you resize SHRLIBRGN, e.g. with SET OMVS command, everything is deleted. LE has another "speciality". If you have lets say the file system mounted under /SYSA/usr/lpp/java and you can also access it with /usr/lpp/java, then /usr/lpp/java/file1 and /SYSA/usr/lpp/java/file1 are different files in the address space. I think it was CDE (but could be wrong) only stores the first used path and for every access with another path name, LE will do a HFSLoad, compare the address to what is already loaded and then HFSDelete if its the same file, which is another overhead. The JVM itself does access same files with different paths. So two caches that could help, but are from my perspective almost unmanageable. And files that are treated as being different, when different paths are used to access them. There is room for improvement, feel free to raise RFEs. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
