The following message is a courtesy copy of an article that has been posted to bit.listserv.ibm-main,alt.folklore.computers as well.
[EMAIL PROTECTED] (Phil Smith III) writes: > This entire discussion is interesting to a VMer. VM has always done > VTIME and TTIME: VTIME is the CPU time used by the guest, TTIME is the > VTIME plus CP overhead. VTIME should be repeatable independent of > system load; TTIME is what varies. VMers talk about "T/V ratios", > i.e., "How well are we doing in terms of overhead?" (Goal=1.00) TTIME "overhead" is frequently viewed as CPU that would not be there if ran on the real machine (w/o vm). VTIME should be approx. the cpu time running on (bare) real machine (w/o) (although it has all the vaguries and caveats with respect to cache misses, interrupts, etc). the jokes have been (for the other mainframe systems) that if customers could run their applications with and w/o the underlying (mainframe) operating systems ... there would be much less bloat in those systems. in vm case, there was significant more pressure to have highly optimized implementation (because of the with and without issue). as a result ... there were various scenarios over the years ... where if customers could configure their other mainframe operating systems to rely on the underlying VM for various functions ... things actually ran faster than on the bare machine. one of those was VS1 "handshaking" ... where it was possible to turn off VS1 virtual paging ... and turn over the responsibility to VM ... it wasn't just that it made VS1 run faster (when running in virtual machine) ... but actually could have VS1 running faster ... than when running w/o VM at all. other recent posts related to this subject: http://www.garlic.com/~lynn/2008c.html#78 CPU time differences for the same job http://www.garlic.com/~lynn/2008c.html#80 Random thoughts http://www.garlic.com/~lynn/2008c.html#81 Random thoughts http://www.garlic.com/~lynn/2008c.html#82 CPU time differences for the same job http://www.garlic.com/~lynn/2008c.html#83 CPU time differences for the same job ---------------------------------------------------------------------- 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
