Edit: maybe you were suggesting the host does direct IO. That is exactly what I recommend. I initially read this differently. Original: If you are running the

Edit: maybe you were suggesting the host does direct IO. That is exactly what I recommend. I initially read this differently. Original: If you are running the host OS you often have little or no say about what happens in the guest OS. Even if you control both it is likely not trivial to get the apps to use direct IO. It could even be harmful to use direct IO because that would mean that writes would not stay in the guest buffer cache, forcing what would have been a cached read or minor fault in the guest into what it sees as a physical read. The written blocks are not going to be shared, except maybe due to KSM. But KSM would do the same if that data was in the guest’s buffer cache if huge pages are not used.