On Mon, 4 Feb 2008 18:16:19 +0100, Miklos Szigetvari wrote: >Hi > >I got this question time to time: >What is the maximum CPU time difference for the same job, between >repeated runs, under different system load ?
Maximum? One could be several times another. Why? One time, with little significant contention, almost all the date referenced is in the High Speed Buffer (or cache) and all virtual address translations are handled in the TLB. Worst case is that almost all memory references cause a HSB miss and the TLB entries are no longer there when they are needed. A memory reference takes several times as long when the data is not in the cache. And if the Translation Lookaside Buffer does not have the information required to translate the virtual address to a real address, that will require a segment table and page table reference, again with the possibility of HSB misses. If the reference is above the bar, there may well be region table references as well. -- Tom Marchant ---------------------------------------------------------------------- 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
