steve@gondor.UUCP (Stephen J. Williams) (04/19/86)
> >What you've said is true of present systems, which tag entries with >process numbers so that they don't have to physically flush the TLB. >It helps that interrupt routines do not completely flush the TLB, but >anything reasonably long-lived, like another process, eventually replace >all of the previous process's TLB entries WHEN SOME OF THEM COULD HAVE >BEEN REUSED - for shared objects like system space, if they were at the same >virtual address. this pushing out of entries will happen ANYHOW. You have TLB entries for lots of small segments, or for one big segment. The effect is the same, replace-wise. >What I mean by a single virtual address space is one where all objects have >unique virtual addresses, where the address ranges of processes do not >collide, where all objects could at least potentially see each other if it >were not for the protection system. There'd be no need for a tag then, >because there is only one translation going on in the system at a time. I still think this is unrealistic. The internal workings of MVS demon- strate the problems that you are trying to solve with bigness. Bigness is not an adequate solution. --Scal