On 11/01/2025 7:33 pm, Colin Paice wrote:
The idea says use the existing Java support to harden the shared
information across IPLs. This means the first start of z/OSMF will be
slow, as today, the next start will use half the CPU.
Please vote for it, or add comments to it.
I'll look into ZOWE - it doesn't even have shared library support enabled!
I looked into the Java shared library support. The thing that deters me
is the warning in the manuals about ahead of time compilation being less
optimized than the JIT compilation so the AOT code may be slower. It's
easy to measure startup time, but not necessarily easy to measure
whether it has an impact on later CPU usage. But if z/OSMF is already
using shared classes it probably makes sense to keep them across an IPL.
On my system z/OSMF starts in 45 seconds, with 48s zIIP time and 3s CP
time. That's not too bad, but I can see how it's a problem if you have
no zIIP and reduced speed CPs.
I actually have no idea what z/OSMF could be doing that takes 50s CPU
time... maybe I'm underestimating it's complexity, but I have a
suspicion that there is something dumb happening there. That's
reinforced by type 92 SMF records which suggest that the same doc.zip
files are being read over and over again - thousands of times!
--
Andrew Rowley
Black Hill Software
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