IBM Mainframe Discussion List <IBM-MAIN@bama.ua.edu> wrote on 06/01/2011 10:33:51 AM:
> Rob Scott <rsc...@rocketsoftware.com> > I know that in the software I am involved in, that "MVCL(*)" for > clearing is used *way* more than any movement purposes as I am a > heavy user of CPOOL services. > > Obviously you can have "fast clear" for objects with lengths that > 256-multiple using n*XC - however I have often wished for a > ZERO=YES option on the CPOOL BUILD so that you are guaranteed a > clean cell for each subsequent CPOOL GET. If anyone else agrees, I > might consider raising a Share requirement .... Such a requirement would likely be rejected. There isn't anything CPOOL can do to obtain better performance for clearing a cell than what you can do in your own code. Clearing done by CPOOL would be guaranteed to be at least marginally slower, and in some cases considerably slower, than clearing done by your code. > (2) Is there any performance difference in MVCL when L2 is zero? Well, at least you can't get any cache misses on the source when the source length is zero. > -----Original Message----- > Behalf Of Charles Mills > Sent: 01 June 2011 14:20 > Subject: Re: What is the current feeling for MVC loop vs. MVCL? > > This thread has been really informative. I am going to put this to > use. I have code that is executing a million or so ~8K MVCLs a day. > I have other things on my plate at the moment but I will replace > that with an MVC loop at some point. > > It seems to me like the ideal way to do this would be to have not > two stages (MVC for 256 and EX'ed MVC) but rather three cases: A > loop with a "hard-coded" or "unrolled" string of 16 MVC's that moved > 4K blocks and incremented registers by 4K on each iteration; > followed by a loop of 256-byte MVCs; followed by an EX'ed MVC for 1 > to 255 bytes. (Obviously each step would be optional depending on > the exact count.) > > Thoughts? 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. 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
