Would it help to have more of those address spaces in SYSSTC so that WLM doesn't try to manage them?
-- Tom Marchant On Tue, 5 Mar 2024 01:03:27 +0000, Graham Harris <harris...@gmail.com> wrote: >A few years back, I did a deep dive into tuning CPU usage across a >multitude of very small z/OS guests under z/VM, and WLM was certainly a big >hitter for many of them, but as there were so many instances, I was able to >see notable differences in WLM use between "LPARs", which was obviously "of >interest". >The upshot seemed to be that WLM costs had a fairly firm relationship with >the number of active address spaces on the "LPAR", presumably down to the >amount of sampling that WLM has to do against each address space every >250ms (I think). I did enquire of IBM as to whether the sampling rate >could be "adjusted", and that came back with a negative response (not >really a surprise). >So the obvious answer may be to only have address spaces started, when they >are only really needed to be there. >Although you may need to assess the cost of stopping/starting those address >spaces, versus the background WLM cost. > > >On Mon, 4 Mar 2024 at 23:08, Wendell Lovewell < >000001e9c0ee0673-dmarc-requ...@listserv.ua.edu> wrote: > >> This is probably a strange question, but is there a way to reduce WLM cpu >> usage? Here's the situation: >> >> - The system is a lightly used development system. Unless something is in >> a loop (very rare), CPU % probably is usually less than 10%. And except >> for system regions & CICS, it's rare to have multiple jobs running >> concurrently. >> - Only one processor defined to the VM. No ZIIP either. >> - We are charged for CPU cycles. >> - WLM is the highest consumer of CPU. JES2, TCPIP, ZFS and SDSFAUX round >> out the top 5 consumers. >> >> There is a lot of information about WLM tuning, but as best I can tell >> almost none of it relates to reducing WLM usage. >> >> From reading the Init & Tuning manual, I'm trying these settings: >> AIMANAGEMENT=NO >> HIPERDISPATCH=NO >> CCCAWMT=450000 >> RMPTTOM=15000 >> >> I was thinking that perhaps reducing whatever processing intervals I could >> might help. But I can't tell these changes made a difference. (I don't >> have a tool to measure WLM usage.) >> >> Any suggestions would be appreciated. >> >> TIA, >> >> Wendell >> >> ---------------------------------------------------------------------- >> For IBM-MAIN subscribe / signoff / archive access instructions, >> send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN >> > >---------------------------------------------------------------------- >For IBM-MAIN subscribe / signoff / archive access instructions, >send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
