Andrea Righi <andrea.righi@xxxxxxxxxxxxx> writes: > The global swap-in readahead policy takes in account the previous access > patterns, using a scaling heuristic to determine the optimal readahead > chunk dynamically. > > This works pretty well in most cases, but like any heuristic there are > specific cases when this approach is not ideal, for example the swapoff > scenario. > > During swapoff we just want to load back into memory all the swapped-out > pages and for this specific use case a fixed-size readahead is more > efficient. > > The specific use case this patch is addressing is to improve swapoff > performance when a VM has been hibernated, resumed and all memory needs > to be forced back to RAM by disabling swap (see the test case below). Why do you need to swapoff after resuming? The swap device isn't used except hibernation? I guess the process is, 1) add swap device to VM 2) hibernate 3) resume 4) swapoff Some pages are swapped out in step 2? If os, can we just set /proc/sys/vm/swappiness to 0 to avoid swapping in step 2? Best Regards, Huang, Ying
