On Thu, 19 Jan 2006 18:06:09 -0500, Shmuel Metz (Seymour J.) wrote: >On 01/19/2006 at 12:40 PM, I said: > >>The I/O interrupt issue has me wondering though -- are folks claiming >>that a zAAP cannot process paging I/O for itself? Surely the JVM is >>not page-fixed in storage, is it? > >Surely it does not need to do its own I/O. Presumably the zAAP is as >capable of issuing a shoulder tap as any other processor.
The zAAP may not have a need to use the 360-MP "shoulder tap" technique to start I/Os or to field I/O interrupts. (I haven't found an appropriate dump yet - I have other things to do now.) But I wouldn't actually suspect it uses that antique technique since (a) zAAPs are limited to processors using PR/SM and (b) Chris, whom I trust, said they don't use it. PR/SM definitely treats the zAAPs special so there may well be sneaky hipervisor techniques used to signal the processors... especially if the processors needing to be signalled are cross-book, for example. I haven't even established whether zAAPs run enabled or disabled for I/O interrupts yet... if they ran disabled for I/O they would, of course, run a lot faster. (I know that I work a lot faster when I'm disabled for interrupts.) Up until they needed to be fed more data; then... not so much faster. The JVMs that run on them certainly have huge working sets so they maybe just suck it all into storage via the general CPs before they duck under the zAAP cloak to do the 'deep computing' and then pop back from Narnia with the answers to life, the universe & everything. I'd be surprised with that outcome but it is, after all, less weird than the things that Orvyl did decades ago at Stanford. (Yes, I know, Orvyl did I/O, but it mostly did its own I/O and pretty much ignored the MVS I/O until it was good & ready to give control back to MVS.) Its on my list of things to learn (after I get done with "more things to learn about CICS file control" which I'm waist-deep in this month & next). -- Tom Schmidt Madison, WI (All of the zAAP stuff seems like a shameful waste of creative programming by Greg D. & Co. just to keep the ISVs from draining the customer base dry.) ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
