On Thu, Apr 11, 2013 at 10:57:26AM -0400, Michael R. Hines wrote: > We have hardware already with front side bus speeds of 13 GB/s. > > We also already have 5 GB/s RDMA hardware, and we will likely > have even faster RDMA hardware in the future. > > This analysis is not factoring into account the cycles it takes to > map the pages before they are checked for duplicate bytes, > regardless whether or not very little of the page is actually > cached on the processor. > > This analysis is also not taking into account the possibility that the > VM may be CPU-bound at the same time that QEMU is competing > to execute is_dup_page(). > > Thus, as you mentioned, a worst-case 5 GB/s memory bandwidth > for is_dup_page() could be very easily reached given the right > conditions - and we do have many workloads both HPC and Multi-tier > which can easily cause QEMU's zero scanning performance to suffer. > > - Michael
Well, then you can make is_dup_page faster e.g. using the pagemap trick as we discussed earlier. Why does management need a "go fast" option? Just make it go fast... -- MST
