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My initial query in the thread "MVS under VM/370 and 3390 DASD" and the conversation has moved into performance tuning, so I'll start a new thread.

Regarding @Bob Polmanters quite helpful info...

I noticed that my user options in the directory for starting MVS did not include REALTIMER and BMX.? I don't know what these options do, but now my ASMCLG test case (prime numbers < 1000) takes 11 seconds under the MVS guest.? This is a good improvement, although still 3-4 times longer than in standalone MVS mode.

I'm using a Raspberry Pi 3B+ and a self-compiled Hercules SDL 4.6.0 for the aarch64 platform.

While the Hercules MAXRATES command shows:

HHC01603I MAXRATES???????????????????????????????????????????????????????????? ?
HHC02268I Highest observed MIPS and IO/s rates:??????????????????????????????? ?
HHC02268I From Mon Nov 27 00:00:00 2023 to Mon Nov 27 09:19:06 2023??????????? ?
HHC02268I MIPS: 19.67965?????????????????????????????????????????????????????? ?
HHC02268I IO/s: 1519?????????????????????????????????????????????????????????? ?
HHC02268I Current interval is 1440 minutes

At 100% CPU (as in during MVS IPL), the MIPS shown by QPROC? is about 1.5.

Something seems wrong about this.? Where are all the other MIPS going?

2 other MVS under VM370 issues I've come upon when shutting down.

JES2 won't stop normally.? I have to do a $p jes2,abend and then reply with purge to the operator message.? Then JES2 will end.

Following that, Z EOD returns IEE480I HALT COMMAND ABEND 800, TERMINATED.

Daniel,

The BMX option in the directory entry allows the virtual channels in the MVS virtual machine to be used in block multiplexor mode.? This means that in many cases, multiple i/o operations can be started and be in progress simultaneously.? This is important because MVS has many address spaces and they are each doing their own thing.? Without BMX, i/o's are much more likely to be single threaded (one at a time).? If you don't specify BMX, then Selector channel is the default, which by its nature only allows a single i/o at a time (per channel).

The REALTIMER option probably wont provide any material performance impact, but it will improve the accuracy of any MVS tasks that depend on timing. It might help MVS with regards to the system scheduler but I am not sure it is measurable.? But you would want to run REALTIMER anyway because if any jobs you run depend on timing services they will be more accurate.? The option causes timer interruptions to be reflected to MVS when they occur; without the option CP will only reflect the interruptions the next time it dispatches MVS (whenever that is).

Some resources you might consider reviewing are GC20-1821-3 VM/370 Operating Systems in a Virtual Machine.? It would tell you about the options above and other available performance items.? Unfortunately, this manual barely mentions MVS; it is more geared to running VM under VM, or DOS/VS under VM.? What I would recommend is looking for GC19-6212-5 VM/SP Rel 5 Running Guest Operating Systems.? Obviously, we don't have all of the features of VM/SP here in VM/370 but the manual contains a ton of information about running MVS under VM and its performance.? You can only use the options that VM/370 supports, but it is a great reference and learning tool within those boundaries.? You can find both manuals on Bitsavers.

As for your question 'where are all of the MIPS going', I can't really answer that.? I also have a Raspberry Pi 3B+ and while I don't have the exact ASMCLG job you ran to create 1000 primes, the times you reported are comparable with what I see on my own Pi 3B+.? I don't think you are going to get much more improvement out of it.

For my serious work and day to day activities, I run on a first-gen Intel i7 processor so there is quite a bit more horsepower to run MVS under VM compared to a Pi 3B.? For example, when I compile the entirety of NJE38, which consists of 16 assembly steps totaling approximately 25,600 lines of code and two linkedit steps, the entire job runs in 52 seconds.? On the Pi 3B+, the same assembly job on a slightly older version on NJE38 (about 2000 lines less code) took 6 minutes, 13 seconds.

My point here is that if you have a faster computer available, MVS under VM can be fairly pleasant in performance.? The Pi 3B would be unbearable for my daily work.? Although, I'd have to admit that the Pi 3B performance feels a lot like what real response times were back in the day on 4341 and 4381 CPUs.

Regards,
Bob

Bob:

From an expectation management perspective, it sounds like I am in the ballpark.

I have a lot of reading and experimentation to do.? I was an MVS operator and programmed in an VM/MVS guest environment as a student and junior programmer back in the mid 1980s.? So, I am pleased with how far I've gotten and the tidbits I've remembered.

Thanks for helping me along.

Jay:

That solved the JES2 shutdown issue for me as well.? I did have to perform a 2nd $p jes2 after draining the reader.

I still get the ABEND on Z EOD.

Daniel,

I was a system programmer back then and I ran VM/370 with a VS1 guest on a S/370-148.? Later we had a 4341 and VM/SP and VS1.? Later still we had a 4381 running VM/SP and MVS as a V=R guest.? Then after a while on the same 4381 we ran VM/HPO with MVS/SP as a V=R guest in PMA mode (Preferred Machine Assist, that Tony H mentioned earlier).? We had a 16M real machine and 60-80 VM/CMS users depending on the time of day.? MVS had 8M of the real memory in the V=R area.? We ran this way in production until 1994.? Performance was always a challenge (mostly the CP paging rate) but "we got 'er done".? So I did this for years and I still remember a lot about it.

Regarding the JES2 shutdown, I have the same issue and Jay is right about the reader being the cause.? I simply don't shut down JES2 and avoid the whole issue.? If I am shutting down the machine, I force MVS with the CP command before I shutdown VM/370.? This allows CP to complete any MVS i/o that might have been in progress.? Wait a second or two then SHUTDOWN.? I've never had any problems ever, by not stopping JES2 completely.

Regards,
Bob