On Jan 19, 2006, at 1:17 PM, Barton Robinson wrote:
Yah, you might save 1% of a processor if you ever swap at 1000 per second or something like that - never bothered to measure it, just know that the cost of swap to vdisk is cheap, fast, and easy to set up, and everybody does it that way for those reasons.
And, ahem, let me plug SWAPGEN, which entirely automates the construction of Linux swap prior to IPL from CMS. Just run SWAPGEN in your PROFILE EXEC, stick /dev/dasdb1 (or whatever) in /etc/fstab, make sure that the DIAG driver is loaded on IPL, and let 'er rip. (Even better: prioritized swap disks.)
Just because you CAN swap to dcss does not mean you should. The only value to dcss has been conjecture, no proof.
I was under the impression that Rob van der Heij (I think) had in fact measured DCSS to be slightly faster.
Me? I use VDISK and SWAPGEN. I understand exactly how it works (for, er, obvious reasons) and it's always been plenty fast enough for me. I haven't measured it either, but I suspect that Barton's right: at the point at which the performance difference becomes noticeable, you have much worse problems than which fast memory-based virtual device you're swapping to.
Adam
