I would expect MVPG to be slow - given its history. If we no longer feel the need to go "the scenic route" :-) maybe it isn't.
Martin Martin Packer, Mainframe Performance Consultant, zChampion Worldwide Banking Center of Excellence, IBM +44-7802-245-584 email: martin_pac...@uk.ibm.com Twitter / Facebook IDs: MartinPacker Blog: https://www.ibm.com/developerworks/mydeveloperworks/blogs/MartinPacker From: Tony Harminc <t...@harminc.net> To: IBM-MAIN@bama.ua.edu Date: 01/06/2011 18:40 Subject: Re: What is the current feeling for MVC loop vs. MVCL? Sent by: IBM Mainframe Discussion List <IBM-MAIN@bama.ua.edu> On 1 June 2011 12:32, Jim Mulder <d10j...@us.ibm.com> wrote: > If your 8K MVCLs have 4K-aligned sources and targets, then > they may be taking advantage of the page mover hardware. In that > case, MVCs could be considerably slower. I had been about to suggest the MVPG instruction, but it's quite possible that MVCL will use the same infrastructure if circumstances are right. One imagines that with fewer options and special cases to evaluate, fewer registers to tie up and none to update, for MVPG the setup would be shorter, and the execution at least as fast. But one's imagination is often not a good guide; I have a rather casual benchmark for these two (that is, MVCL of 4k on a page boundary vs MVPG with no fancy options) that shows MVPG just barely beating MVCL on a z10, and losing heavily on all earlier machines I had access to (P390, zPDT, MP3000, FLEX/ES and z9). John Gilmore's points are well taken. If I may suggest one more, loosely put, it is to use instructions for what they are usually used for (which is, even more approximately, what they are documented to be used for). This is likely to take advantage of hardware optimizations over time without forcing a tight binding to the hardware of the day. The assembler programmer does not have an easy way to recompile and take advantage of whatever the hardware implementors and compiler designers have come up with since the code was written. Tony H. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html Unless stated otherwise above: IBM United Kingdom Limited - Registered in England and Wales with number 741598. Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
