On 1/19/06, Adam Thornton <[EMAIL PROTECTED]> wrote: > I was under the impression that Rob van der Heij (I think) had in > fact measured DCSS to be slightly faster.
Yes, and we're getting to the point where he's also interested when I can measure it... Indeed, I showed that in similar scenario we could swap 50% more while burning a CPU on it. Let's assume the test program did not use any cycles, and only caused the swapping. Doing 40 MB/s to VDISK means 100 nS per page. With DCSS the rate was 50% higher, so we would assume 65 nS per page. Now what would be an average swap rate you feel comfortable with when the server is busy? 500 pages per second probably sounds at the high end? That means 5% vs 3% when the server is busy. And when it's used only 5% of the time... >From a pure technical point of view, swapping to DCSS is much more elegant because you copy a page under SIE and don't step out to CP to interpret a channel program. But the drawback is that the DCSS is relatively small and requires additional management structures in the Linux virtual machine memory. I see some goodness for very small virtual machines, I think. Rob -- Rob van der Heij rvdheij @ gmail.com Velocity Software, Inc
