We just got a z15 and I have not tested MVCL vs MVC loop, but on all prior machines a MVC loop beat a MVCL up to about 32K. Over 32K MVCL is the way to go. In our environment we rarely are moving more than 32K. We built a $MVC macro with 3 parameters, destination, source and length and use that.
FYI - MVCL is a micro-code (milli-code, call it what you want) instruction. There is a hefty startup and end cost to micro-code instructions. MVCL only really gets going when it can use the internal move page function. That has to be moving whole pages and they have to be page aligned. CLCL and similar instructions, at least used to, suffer the same type of startup costs. Chris Blaicher Technical Architect Precisely.com -----Original Message----- From: IBM Mainframe Assembler List [mailto:ASSEMBLER-LIST@LISTSERV.UGA.EDU] On Behalf Of Mike Hochee Sent: Tuesday, October 20, 2020 12:40 PM To: ASSEMBLER-LIST@LISTSERV.UGA.EDU Subject: Re: Conditional MVCL macro? This message originated Externally. Use proper judgement and caution with attachments, links, or responses. Really interesting thread to start the day with! Our experience has been that the MVC loops are typically faster, up to a point, that being about 30-40 instructions in the pipeline and as mentioned, and this seemed very processor dependent. However when source and target operands happen to both be aligned on a page boundary, then the opportunity exists for the async data mover to kick in if a move long is being used. I think this applied to both MVCL and MVCLE, but not sure. So ideally a macro would want to utilize both MVCs and MVCL/E. More grist for the mill! -----Original Message----- From: IBM Mainframe Assembler List [mailto:ASSEMBLER-LIST@LISTSERV.UGA.EDU] On Behalf Of baron_car...@technologist.com Sent: Tuesday, October 20, 2020 12:12 PM To: ASSEMBLER-LIST@LISTSERV.UGA.EDU Subject: Re: Conditional MVCL macro? Caution! This message was sent from outside your organization. The COBOL compiler for a 4000 byte move, from to the same with OPT(2) generates LAY R10,5072(,R9) FROM LA R7,1072(,R9) TO MVC 0(256,R7),0(R10) MVC 256(256,R7),256(R10) MVC 512(256,R7),512(R10) MVC 768(256,R7),768(R10) MVC 1024(256,R7),1024(R10) MVC 1280(256,R7),1280(R10) MVC 1536(256,R7),1536(R10) MVC 1792(256,R7),1792(R10) MVC 2048(256,R7),2048(R10) MVC 2304(256,R7),2304(R10) MVC 2560(256,R7),2560(R10) MVC 2816(256,R7),2816(R10) MVC 3072(256,R7),3072(R10) MVC 3328(256,R7),3328(R10) MVC 3584(256,R7),3584(R10) MVC 3840(160,R7),3840(R10) However for 5000 bytes it generates: LAY R7,6072(,R9) LA R10,0(,R7) LA R7,1072(,R9) LHI R11,0x13 EQU * MVC 0(256,R7),0(R10) LA R10,256(,R10) LA R7,256(,R7) BRCT R11,L0128 MVC 0(136,R7),0(R10) And yes the change occurred at 4097 bytes. -----Original Message----- From: IBM Mainframe Assembler List <ASSEMBLER-LIST@LISTSERV.UGA.EDU> On Behalf Of Charles Mills Sent: Tuesday, October 20, 2020 10:54 To: ASSEMBLER-LIST@LISTSERV.UGA.EDU Subject: Re: Conditional MVCL macro? @Ed, can you elaborate a little on your reasoning? (Not doubting it; just curious.) Is it that the interruptibility provides a significant improvement over MVCL? Or the support for lengths greater than 16M? Or ... ? When I asked Dr. Shum about move strategies he seemed to indicate that for data that was already or would soon anyway be in cache an MVC loop was generally faster than MVCL. (I did not ask about MVCLE at the time; not sure why. He did not suggest it.) Charles -----Original Message----- From: IBM Mainframe Assembler List [mailto:ASSEMBLER-LIST@LISTSERV.UGA.EDU] On Behalf Of Ed Jaffe Sent: Tuesday, October 20, 2020 6:52 AM To: ASSEMBLER-LIST@LISTSERV.UGA.EDU Subject: Re: Conditional MVCL macro? We've switched almost exclusively to MVCLE except for short, fixed-length moves.
