Hi, Paolo, As you said the memory pages may have already be touched by the guest, although it still cause page fault from the VM. So my question is will KVM pre-allocate some physical pages (by calling get_user_page_fast) to the guest? If so, when a user-space program in the guest requests for pages, how does KVM decide which pre-allocated physical pages are to be allocated? Because in this microbenchmark, for each virtual page fault in the guest, I can trace there is a corresponding kvm_page_fault event, but not mm_alloc_page event (which is the function of allocating page by the buddy allocator). Thanks in advance. - Steven On Wed, Sep 17, 2014 at 3:22 PM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > Il 17/09/2014 19:19, Steven ha scritto: >> I think get_user_pages or get_user_pages finally will call >> mm_page_alloc, right?. >> However, for the small size array, I observer many >> kmem_cache_alloc_node and kmalloc_node physical page allocation, but >> very few mm_page_alloc trace. So will the host kernel assign the >> memory to the VM from slab allocator? Thanks. > > I don't think so. Likely the memory had already been touched by the guest. > > Paolo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
