>>>> >>>> Also one reason why I am not a fan of working with anything less than >>>> PMD order is because there have been issues in the past with false >>>> memory leaks being created when hints were provided on THP pages that >>>> essentially fragmented them. I guess hugepaged went through and >>>> started trying to reassemble the huge pages and as a result there have >>>> been apps that ended up consuming more memory than they would have >>>> otherwise since they were using fragments of THP pages after doing an >>>> MADV_DONTNEED on sections of the page. >>> >>> I understand your concerns, but we should not let bugs in the hypervisor >>> dictate the design. Bugs are there to be fixed. Interesting read, >>> though, thanks! >> >> Right but if we break up a huge page we are then creating >> more work for hypervisor to reassemble it. > > Yes, but the hypervisor can decide what to do. E.g. on s390x there are > no THP, so nothing to break up.
To clarify as that might be confusing: No THP in a KVM guest mapping for now. > > It is all very complicated :) > -- Thanks, David / dhildenb
