IBM Mainframe Discussion List <IBM-MAIN@bama.ua.edu> wrote on 04/15/2009 01:05:34 PM:
> >> We did that and found *one* instruction that was so slow, and > executed so often, it brought our product to its "knees". > >> > > > > Please name and shame the instruction > > > > LMD. We used it in an unstack routine, that had been updated to support > AMODE(64) execution, without understanding just how slow it was (and how > often we executed it). Code got into the field for early testing and > customers complained. A product called STROBE pointed to the 64-byte > block containing this instruction. We replaced it with other > instructions and the problem was resolved. That's why LMD has the following Programming Note: 3. The combination of a LOAD MULTIPLE instruction and a LOAD MULTIPLE HIGH instruction provides equal or better performance than a LOAD MULTIPLE DISJOINT instruction for the same register range. LOAD MULTIPLE DIS- JOINT is for use when the second or fourth operand must be addressed by means of one of the registers loaded. Jim Mulder z/OS System Test IBM Corp. Poughkeepsie, NY ---------------------------------------------------------------------- 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
