re: http://www.garlic.com/~lynn/2012o.html#30 Regarding Time Sharing
oh, old presentation at fall atlantic share meeting in 1968 http://www.garlic.com/~lynn/94.html#18 on MFT14 & CP67. CP67 had been installed in the univ last week of Jan68. Univ. continued to run OS/360 (in 360/65 mode on 360/67) production during the period. I was the support person for os/360 ... but did get to play with cp67 some on the weekends. most of the presentation was about cp67 pathlength rewrite during spring & summer 1968 (before I really got in to totally rewritting virtual memory and dynamic adaptive resource management). it does reference that I had completely redone os/360 sysgen ... hand reordering much of the stuff to achieve optimal disk operation (and while I was at it, changing it so it could be done in the product jobstream) standard sysgen out of the box took a over 30 seconds elapsed time (with hasp, before hasp, it was well over minute) for typical univ. student job workload (3step fortgclg, before watfor). This was mostly job scheduler & allocation doing approx. 10seconds of loading linklib and svclib members per job step. Careful sysgen reorder got it down to 12.9 seconds elapsed time (note quite three times faster). the re-order accomplished two things 1) it group the highest used linklib & svclib members together at the start of PDS dataset ... minimize arm seek between PDS directory lookup and loading member and 2) placed the highest used members at the front of the PDS directory. full cylinder 2314 PDS directory search took 20 revolutions at 2000rev/min .. well over half-second elapsed time during which time channel, controller, and disk were locked out. Even half-cylinder pds directory multi-track search would take 1/3rd second (per member load). Making sure that the highest used members were on the first track or two of the PDS directory ... could reduce PDS directory member lookup to 40-50 mills. 2314 reference from bitsaver http://bitsavers.org/pdf/ibm/dasd/A26-3599-4_2314_Sep69.pdf past posts on dynamic adaptive resource management http://www.garlic.com/~lynn/subtopic.html#fairshare past posts on virtual memory management http://www.garlic.com/~lynn/subtopic.html#wsclock past posts on getting to play disk engineer http://www.garlic.com/~lynn/subtopic.html#disk past posts on ckd dasd, multi-track search, fba (including being told that even if I gave MVS fully integrated & tested FBA support, i still needed an additional $26M new business profit) http://www.garlic.com/~lynn/submain.html#dasd -- virtualization experience starting Jan1968, online at home since Mar1970 ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
