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This group is for all folks running the original IBM VM/370 Release 6 operating system (or later (e.g. VMTCE (Community Edition)) on Hercules. Like the other early IBM operating systems this version has always been in the public domain and so can be freely distributed. The base version as supplied by IBM is lacking in many facilities. IBM solved this by providing additional extension products which were licensed and so are not available. There are however many user enhancements available which can be installed. In addition, in order to get users up and running quickly updated "releases" of VM/370 included the most popular updates are available for download, so novices can start to learn VM without having to delve into the system internals. It is intended that this wiki will provide information on the base release and these updates.
The available versions are here :-
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Re: VM/370 Hercules Optimisation
My experience was that MUSIC performed really well under VM provided it had enough memory and even better still if it was locked in storage. It was possible to support over a hundred users on MUSIC running on VM doing edit/compile/run cycles with the same sort of machine resources that would be crawling when a quarter of that number of CMS users were doing similar work. If it was attempted to have both of these categories of users working at the same time, the MUSIC users really suffered, despite all sorts of attempts to give preferential treatment to the VM userid running MUSIC. There were all sorts of dire warnings in the MUSIC administrator guide to not allow VM to page MUSIC, but in practice we found the effects were not quite as bad as the warnings suggested they would be, at least when the CMS users weren't beating on it. This was on an Amdahl 5870 (AP) with 64MB of real storage, VM/HPO and a virtual storage size of 12MB for MUSIC (because the VM sysprog wasn't willing to risk giving it 16MB). Regards, Peter Coghlan. |
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Re: VM/370 Hercules Optimisation
开云体育Steven, ? I think it was Joe who mentioned the assists. To be honest while I think for CMS, VM is the “bees knees”, when you try to run MVS in a VM the wheels can fall off the car because of the need to maintain shadow page tables. So in VM/370 all guests run real problem state and even when running V=R they don’t have access to real page zero. All interrupts get passed to CP not the Guest. CP then has to either simulate them or reflect them to the OS. For an OS like CMS which runs DAT off this isn’t a huge problem. When running multiple users who “IPL CMS” things are improved because each user does share most of the CMS nucleus as a “Discontigous Saved Segment”, a piece of read only memory that usually sits at the top of memory and so tends to stay in real store. Again this usually isn’t relevant for Hercules because we typically only have one user but the CMS in all the releases available for download are built like that. ? On the other hand MVS wants to do its own paging, so every time MVS changes the page tables, an interrupt is generated and VM has to update its shadow page tables. There are several ways to reduce this overhead. If you are only running one copy of MVS you can dedicate some low store to it, and so run it as V=R. ?but if you have multiple machines obviously only one can be v=r. The assists are really useful here. Some releases of “OS” also have handshake features that allows the OS to pass information to CP and reduce the overhead. ? Someone mentioned poor performance with MUSIC, well I suspect what killed MUSIC under VM was the paging overhead… ? … on the other hand some releases of DOS reputedly ran better under VM because the OS paging could be disabled, and the CP paging was much better… ? For those interested GC20-1821 has more info… ? ? but the some of the facilities described in there are SEPP or BSEPP which we don’t have/// ? Dave ? ? ? From: [email protected] <[email protected]> On Behalf Of Steven Fosdick
Sent: 30 January 2020 16:47 To: [email protected] Subject: Re: [h390-vm] VM/370 Hercules Optimisation ? On Thu, 30 Jan 2020 at 15:57, Dave Wade <dave.g4ugm@...> wrote:
? Was Adrian thinking that a page fault* would be the cause of the I/O?? Presumably if one accesses an address from within CMS that is not, at that moment, mapped to real memory it is CP, not CMS, that handles the page fault? ? * is there an IBM name for this as there seems to be for most other things.?
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Re: VM/370 Hercules Optimisation
On Thu, Jan 30, 2020 at 04:46 PM, Steven Fosdick wrote:
Was Adrian thinkingProbably overthinking! It sounds like at best we are talking about marginal differences. Anyway I have my Dockerfile working so I will try some speed tests with different configs over the weekend. Thanks for all the advice :-) |
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Re: VM/370 Hercules Optimisation
On Thu, 30 Jan 2020 at 15:57, Dave Wade <dave.g4ugm@...> wrote:
Was Adrian thinking that a page fault* would be the cause of the I/O?? Presumably if one accesses an address from within CMS that is not, at that moment, mapped to real memory it is CP, not CMS, that handles the page fault? * is there an IBM name for this as there seems to be for most other things.? |
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Re: VM/370 Hercules Optimisation
开云体育Joe, ? Not really much to do with IO. Hercules implements these as was mentioned earlier. Shadow Table Bypass is only relevant when running a guest OS that use virtual memory. CMS only runs with DAT off … ? Dave ? From: [email protected] <[email protected]> On Behalf Of Joe Monk
Sent: 30 January 2020 15:49 To: [email protected] Subject: Re: [h390-vm] VM/370 Hercules Optimisation ? So according to this guide there were VMASSISTS in ECPS:VM ?... ? ? Joe ? On Thu, Jan 30, 2020 at 9:37 AM adriansutherland67 <adrian@...> wrote:
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Re: VM/370 Hercules Optimisation
开云体育Adrian For CMS its pretty much the same!. That’s the who benefit of channels. You send the SIOs to the channel and the channel and controllers work out what to do. Dave ? From: [email protected] <[email protected]> On Behalf Of adriansutherland67
Sent: 30 January 2020 15:38 To: [email protected] Subject: Re: [h390-vm] VM/370 Hercules Optimisation ? On Thu, Jan 30, 2020 at 01:31 PM, Joe Monk wrote:
Cool - and in terms of CP (or VM/370) code is there much difference? |
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Re: VM/370 Hercules Optimisation
开云体育Back when I was in college, the administrative center was run on a 4341, and a 4331 was what supported all the campus’ student computing needs. ?I worked in the lab as an RJE operator.I think back then it was mostly DOS/VSE with POWER for the campus systems, and then later VM/360 with DOS/VSE running as a VM and eventually MUSIC as another VM for our first interactive computing for the students. ? I’m pretty sure the Admin 4341 was running MVS along with CICS. I liked MUSIC a lot, but the overall load was WAY more than the machine could handle and RJE job turnaround went up to 24 hours and beyond. ?I burned a lot of midnight oil keeping the printer fed so that the wait times didn’t just keep escalating. Whether that could be attributed to 43x1 channel performance would be interesting to discover. Fun times. Scott
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Re: VM/370 Hercules Optimisation
So according to this guide there were VMASSISTS in ECPS:VM ?... Joe On Thu, Jan 30, 2020 at 9:37 AM adriansutherland67 <adrian@...> wrote: On Thu, Jan 30, 2020 at 01:31 PM, Joe Monk wrote: |
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Re: VM/370 Hercules Optimisation
开云体育Joe, Interesting! Contrast that with the top of page 65:- ? GENERAL OPERATION OF THE CHANNELS The channels in the 4341 Processor are microcode and hardware controlled. They are integrated channels and, thus, share the use of certain hardware with the instruction processing function, such as the arithmetic logic unit, byte shifter, and control storage. ? The small 43xx were notorious for poor IO performance under heavy load reputedly because of this…. ? Dave ? From: [email protected] <[email protected]> On Behalf Of Joe Monk
Sent: 30 January 2020 12:02 To: [email protected] Subject: Re: [h390-vm] VM/370 Hercules Optimisation ? Dave, ? Huh? To quote the manual: ? "The 4341?Processor generates less?total?interference with instruction execution than intermediate-scale?System/360 and System/370?processors because the?amount?of time required?to transfer?a?byte?of?data?between?processor storage?and?the channel data buffer during?an?I/O operation?is?much?less?(64?bytes are transferred?in?4 microseconds?in the?4341 Processor?versus?4?bytes transferred to or?from?processor storage in?.54 microseconds?in the?Model 148,?for example)." ? I dont?see how that can degrade CPU performance for high I/O. In fact, in a high I/O situation, wouldnt?it help?? ? If 4 bytes are transferred in half a microsecond, that means 64 bytes could be transferred in 32 microseconds, versus 4 microseconds on a 4341... ? Joe ? On Thu, Jan 30, 2020 at 3:47 AM Dave Wade <dave.g4ugm@...> wrote:
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Re: VM/370 Hercules Optimisation
"I guess, in the context of hercules, we are looking for the device which required the fewest S/370 CPU cycles so that most of the work is done in?x86-64 land, but also one where the engineers didn't have to build in any weird waits or timing stuff into the CP drivers." If you look at the actual Hercules code, you can see that there is virtually no difference in how the various types of DASD are implemented... Joe On Thu, Jan 30, 2020 at 6:37 AM adriansutherland67 <adrian@...> wrote: On Thu, Jan 30, 2020 at 09:47 AM, Dave Wade wrote: |
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Re: VM/370 Hercules Optimisation
On Thu, Jan 30, 2020 at 09:47 AM, Dave Wade wrote:
On the low end 43xx boxes in effect the channel is implemented using some of the main CPU so device that generate high IO can degrade CPU performance…I guess, in the context of hercules, we are looking for the device which required the fewest S/370 CPU cycles so that most of the work is done in?x86-64 land, but also one where the engineers didn't have to build in any weird waits or timing stuff into the CP drivers. So it doesn't matter if the device was as slow as a dog in real life - as long as it delivers the requested block to the s/370 and VM/370 doesn't care if the interrupt (or whatever) happens VERY quickly. Also, perhaps there were some file system ASSISTS? Does that suggest anything to anyone? |
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Re: VM/370 Hercules Optimisation
Dave, The 2305 uses a block multiplexor channel ... "The 2835 storage Control and 2305 Fixed Head Storage Module form a large capacity, high -speed direct access storage facility for general purpose data storage and system residence.?It?attaches to the central processing unit through a block multiplexor channel, and operates under direct program control of the CPU." Joe On Thu, Jan 30, 2020 at 3:47 AM Dave Wade <dave.g4ugm@...> wrote:
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Re: VM/370 Hercules Optimisation
Dave, Huh? To quote the manual: "The 4341?Processor generates less?total?interference with instruction execution than intermediate-scale?System/360 and System/370?processors because the?amount?of time required?to transfer?a?byte?of?data?between?processor storage?and?the channel data buffer during?an?I/O operation?is?much?less?(64?bytes are transferred?in?4 microseconds?in the?4341 Processor?versus?4?bytes transferred to or?from?processor storage in?.54 microseconds?in the?Model 148,?for example)." If 4 bytes are transferred in half a microsecond, that means 64 bytes could be transferred in 32 microseconds, versus 4 microseconds on a 4341... Joe On Thu, Jan 30, 2020 at 3:47 AM Dave Wade <dave.g4ugm@...> wrote:
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Re: VM/370 Hercules Optimisation
开云体育Doug, On the low end 43xx boxes in effect the channel is implemented using some of the main CPU so device that generate high IO can degrade CPU performance… ? ? page 64. ? The channel throughputs are on 67. Your issue with the 2305 may have been that it needed a selector channel an whilst the machine can do that it reduces the number of block multiplexor channels… ? Dave ? From: [email protected] <[email protected]> On Behalf Of Doug Wegscheid
Sent: 30 January 2020 03:21 To: [email protected] Subject: Re: [h390-vm] VM/370 Hercules Optimisation ? 2305 was nice because of no seek time. In an Hercules emulated environment, probably doesn't make a difference. ? I was on the periphery of a 360/75 MVT -> 4341 MVT under VM transition (I got to do some MVT<->VM integration, much fun! HASP, CP SPOOL, VMCS....). 2305 was our MVT SYSRES. I heard that the channels on the 4341 couldn't keep up with the 2305, even if we dedicated it to the MVT virtual machine,and we had to drop back to a 3330 SYSRES. I'm not sure that last bit is accurate. ? The /75 sure was cool, though... ? On Wednesday, January 29, 2020, 2:48:12 PM EST, Drew Derbyshire <swhobbit@...> wrote: ? ? On 1/29/20 4:15 AM, adriansutherland67 wrote: |
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Re: CP Query
开云体育On 1/29/20 7:22 PM, Doug Wegscheid
wrote:
Have both.
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Re: VM/370 Hercules Optimisation
开云体育On 1/29/20 7:21 PM, Doug Wegscheid
wrote:
SSDs don't HAVE seek time, and for that matter modern I/O speed (even USB 2) versus 1970s parallel channel performance is no contest.?? But no one told VM all that, so it may still have the bias to emulated 2305s. For me, with real disk I/O to a USB 3 connected 500GB Samsung SSD on a 2 GB system with 1272 MB for buffer/cache, I/O is probably relatively speaking the one of fastest things on the system. -ahd- |
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Re: CP Query
I would ask why shouldn't X Y and Z report their own level, and not have to fold that into CP?
On Wednesday, January 29, 2020, 2:41:40 PM EST, Drew Derbyshire <swhobbit@...> wrote:
On 1/29/20 3:59 AM, Peter Coghlan wrote: > > However, I have to question if QUERY CPLEVEL is the right place to put this > information seeing as a Sixpack distribution is really composed of a certain > level of CP features, a certain level of CMS features and a bunch of compilers > and applications while QUERY CPLEVEL only describes one aspect of this. > Since the SixPakc include CP changes, it's definitively of? one the right places. Both CP and CMS should be report what their build level and their build date; so should the other components. Why would one omit the information from CP Q CPLEVEL just because it can't report X Y or Z which are not part of CP? |
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Re: VM/370 Hercules Optimisation
2305 was nice because of no seek time. In an Hercules emulated environment, probably doesn't make a difference. I was on the periphery of a 360/75 MVT -> 4341 MVT under VM transition (I got to do some MVT<->VM integration, much fun! HASP, CP SPOOL, VMCS....). 2305 was our MVT SYSRES. I heard that the channels on the 4341 couldn't keep up with the 2305, even if we dedicated it to the MVT virtual machine,and we had to drop back to a 3330 SYSRES. I'm not sure that last bit is accurate. The /75 sure was cool, though...
On Wednesday, January 29, 2020, 2:48:12 PM EST, Drew Derbyshire <swhobbit@...> wrote:
On 1/29/20 4:15 AM, adriansutherland67 wrote: > > For memory paging - I was wondering if IBM had a paging memory device > (clearly not - thanks). Therefore (1) I am going to go ahead with > experimenting with a small DASD drive for paging. I thought there was a bias towards 2305 devices for paging, but too much time hanging out with the documents for a certain 4361 and it's VM/SP flavor, my brain is probably fogged. -ahd- |
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Re: CP Query
开云体育Share file, didn’t want to undo existing stuff ? Dave ? From: [email protected] <[email protected]> On Behalf Of adriansutherland67
Sent: 29 January 2020 22:33 To: [email protected] Subject: Re: [h390-vm] CP Query ? On Wed, Jan 29, 2020 at 07:41 PM, Drew Derbyshire wrote:
Indeed, and I was just wondering how to report CMSLIB version, and of course GCC brexx etc all have versions. |