ridiculous GBLPAGES Autogen values under VMS 7.2-2

[John Gillings]

Jess, please recalibrate your definition of "reasonable" & rediculous to current resource levels!

This is intended behaviour. By default, AUTOGEN will set GBLPAGES to 3/4 of physical memory. On VAX, the cost of GBLPAGES was 4 bytes of physically resident memory for every 128 global pages, but that's no longer an issue on Alpha.

Alpha page table entries are 8 bytes, one per global page, but the page table pages themselves are in virtual memory - S2 space, and initially demand zero (so they don't actually exist). All that's needed are the system page table pages required to map the global page table. For GBLPAGES set to 3/4 of total physical memory, that's a bit less than 1 millionth of physical memory. In other words, the "penalty" for a high value of GBLPAGES is negligible if you don't use them.

This deliberate change to AUTOGEN is intended to encourage the use of RMS global buffers. So, if you're NOT using a significant proportion of GBLPAGES, you should be turning on global buffers and reaping the performance reward (remember, as Hein says, there is only ONE WRONG number of global buffers on an RMS file - ZERO!).

On the other hand, both GBLPAGES and GBLPAGFIL are dynamic, so feel free to adjust them up or down whenever you like.