On Sat, 2 Jan 2010 15:37:15 -0500, Jim Mulder <[email protected]> wrote: > > I was told that compressed pointers for storage below 32GB fit >into a smaller space, so more compressed pointers fit in a cache >line, leading to more effective cache utilization. Performance is >all about the caches these days. I am not a Java person. I don't >know what a compressed pointer is. >
>From what (I think) I understand / remember from what I heard at SHARE, it is addresses of large object pages. And since they are in 1M increments / boundaries, the lower 3 bytes aren't needed as long as the "thing" that needs those addresses understands what they are. (So obviously you need z/OS 1.9 or above and a z10 with large page support turned on take advantage of this new function). >> > I'm still intrigued that the (undocumented) option's name >> > contains the substring "32G". Is 32GiB the size of a particular >> > granule in 64-bit storage management? Or might the "32" refer >> > to a fictitious "32-bit" addressing capability? >> How many 32bit pointers can fit in 30G? I think 4026531840 - which would represent 3840T of virtual storage (if my math is correct - which it probably isn't). I'm getting dizzy thinking about these large numbers. > > The range from 2GB to 32GB is set aside for a particular intended >user, which is the JVM. > On Mon, 4 Jan 2010 07:58:37 -0600, McKown, John <[email protected]> wrote: >> >> The storage between 2g and 4g is NOT accessible in 31 bit mode. >> > >You're right! So, why bother and how does it improve performance? I guess we'll never know. It is likely "proprietary". Since it was talked about at SHARE, I don't think it's proprietary. It's just not GUPI. Mark -- Mark Zelden Sr. Software and Systems Architect - z/OS Team Lead Zurich North America / Farmers Insurance Group - ZFUS G-ITO mailto:[email protected] z/OS Systems Programming expert at http://expertanswercenter.techtarget.com/ Mark's MVS Utilities: http://home.flash.net/~mzelden/mvsutil.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
