On Fri, 27 Nov 2020 08:55:35 -0500, Peter Relson wrote: ><snip> >That fits with my understanding that those bits to the right are to >ensure STCK uniqueness in a multi-CPU system, and STCK doesn't >guarantee uniqueness on any system -- two readings may be taken >between increments. ></snip> > >STCK values are guaranteed to be unique within an LPAR (whether 1-CPU or >multi-CPU). > I stand corrected. Read "STCKF" for my second use of "STCK". Typo, I think.
My understanding is that in the Bad Old Days when each CPU had its own TOD clock, the low-order bits were different for each CPU ensuring uniqueness. Thus it might be possible that if a task were dispatched on a different CPU between readings the interval might appear negative. I doubt that the re-dispatch could be performed so quickly. -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
