The following is a snip from a program which I just ran on our Z10 whose characteristics are shown last below. The program first moved 65536 bytes from one location to another using MVCL and did this 1 million times. You'll see it took ~56 seconds. Then the same number of bytes were moved using 1 million MVC loops. This took ~8 seconds. Finally, the same number of bytes were moved 1 million times using MVCLE.
I have run this program on every CEC that I have had available to me and the results are always relatively the same although the actual numbers change. MVCL has some extraordinarily useful functions: Truncation, padding and returning addresses and lengths after MVCL. Each of these would have to be done manually if a MVC loop were used and these instructions would have to be added into the total time for MVC loops. And, yes, I wrote a MVCL macro. But once one tries to support the case where bits 8 through 31 of R1+1 and R2+1 are not equal the macro gets very big and very awkward. And the macro would have to return the 4 registers with contents the same as MVCL would. 1 MILLION MVCL INSTRUCTIONS IN SECONDS 55.961093 1 MILLION MVC LOOPS IN SECONDS 8.389260 1 MILLION MVCLE INSTRUCTIONS IN SECONDS 115.548643 OPERATING SYSTEM= HBB7770SP7.1.2 HBB7770 CPU ID FROM STIDP: TYPE=2098 VERSION=00 SERIAL=00XXXX EXECUTION ENVIRONMENT: LPAR=YES VM=NO CPU ID FROM STSI: MANUF=IBM TYPE=2098 MODEL=R03 SERIAL=00000000000XXXXX VERSION CODE FROM CONVERSION TABLE= ROLLING 4-HOUR AVERAGE UTILIZATION IS 23 MSUS LPAR XXXX IS UNCAPPED IN A 89 MSU CEC ADJ FACTOR 1946 ACCUM WEIGHT 6385225 TIMES ACCUM 23219 LPAR_NAME=XXXX LPAR_ID=0003 LPAR_SIZE=89 CEC_SIZE=89 ARCH=Z/ARCHITECTURE > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:IBM-MAIN@bama.ua.edu] On > Behalf Of Charles Mills > Sent: Tuesday, May 31, 2011 2:02 PM > To: IBM-MAIN@bama.ua.edu > Subject: Re: What is the current feeling for MVC loop vs. MVCL? > > Just my uninformed opinion, but it's hard for me to see how an MVC loop > could be faster. Both are interruptible. (MVC is not but an MVC *loop* is.) > Both update registers (okay, three versus four). > > I know microcode is not magic but gee, if MVC were faster than whatever > MVCL > does, wouldn't the microcode writers just have used an MVC loop instead of > what they did use for MVCL? > > My uninformed opinion is that MVCL worst case should be no slower than an > MVC loop for indeterminate length moves of possibly more than 256 bytes > (and > as a side benefit, it is a heck of a lot easier to use in that situation, > unless you happen to be very short on spare registers). > > Charles > > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:IBM-MAIN@bama.ua.edu] On > Behalf > Of Mike Schwab > Sent: Tuesday, May 31, 2011 1:35 PM > To: IBM-MAIN@bama.ua.edu > Subject: Re: What is the current feeling for MVC loop vs. MVCL? > > How about a macro to replace MVCL with a loop using the same registers but > using MVC? Anyone ever write one? > > ---------------------------------------------------------------------- > 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 ---------------------------------------------------------------------- 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 ---------------------------------------------------------------------- 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
