Il 31/01/2013 10:48, Gleb Natapov ha scritto: >> Also I notice that the bottle neck in migrating unmapped pages is the >> detection of those pages >> because we map the pages in order to check them, for a large guest this is >> very expensive as mapping a page >> results in a page fault in the host. >> So what will be very helpful is actually locating those pages without >> mapping them >> which looks very complicated. >> > What is wrong with mincore()?
As Avi said, it returns false if the memory is in swap. Note that while we do take a page fault, the recent kernel patch to introduce a huge zero page might have reduced the cost in terms of both clear_page and cache misses. Paolo
