Ed OK, I will bite...
>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 Rob Scott Developer Rocket Software 275 Grove Street * Newton, MA 02466-2272 * USA Tel: +1.617.614.2305 Email: [email protected] Web: www.rocketsoftware.com -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Edward Jaffe Sent: 15 April 2009 16:08 To: [email protected] Subject: Re: The speed of the 64 bit code Miklos Szigetvari wrote: > We have converted our complex C++ document generation application to > 64 bit mode. > With different test cases, we see the average CPU time is about 4% > higher in 64 bit mode as in 32, This is not an altogether unexpected outcome. There are many possible reasons: your programs and data areas might be larger--thus taking longer to load/move/page, address translation involving a region 3rd will be slower than segment-only translation (imagine what would happen with region 2nd--stay below 4TB!), and so forth. All code might not be apples to apples either. For example, if any service you're calling uses BAKR for 64-bit callers, yet traditional STM/LAM, STAM/LAM, for 31-bit callers, it will run noticeably slower. It might be worth using HIS or a commercial execution analyzer product to look for program "hot spots". We did that and found *one* instruction that was so slow, and executed so often, it brought our product to its "knees". Replacing that one instruction with a multi-instruction equivalent made the performance problem disappear. (Of course, this was an assembler language program. You might not have as much control with C++ over such things. But, the analysis can still be valuable.) -- Edward E Jaffe Phoenix Software International, Inc 5200 W Century Blvd, Suite 800 Los Angeles, CA 90045 310-338-0400 x318 [email protected] http://www.phoenixsoftware.com/ ---------------------------------------------------------------------- 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 ---------------------------------------------------------------------- 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
