On Tue, Aug 18, 2020 at 12:27 AM SeongJae Park <sjpark@xxxxxxxxxx> wrote:
>
> From: SeongJae Park <sjpark@xxxxxxxxx>
>
> This commit implements the four callbacks (->init_target_regions,
> ->update_target_regions, ->prepare_access_check, and ->check_accesses)
> for the basic access monitoring of the physical memory address space.
> By setting the callback pointers to point those, users can easily
> monitor the accesses to the physical memory.
>
> Internally, it uses the PTE Accessed bit, as similar to that of the
> virtual memory support. Also, it supports only user memory pages, as
> idle page tracking also does, for the same reason. If the monitoring
> target physical memory address range contains non-user memory pages,
> access check of the pages will do nothing but simply treat the pages as
> not accessed.
>
> Users who want to use other access check primitives and/or monitor the
> non-user memory regions could implement and use their own callbacks.
>
> Signed-off-by: SeongJae Park <sjpark@xxxxxxxxx>
[snip]
> +static void damon_phys_mkold(unsigned long paddr)
> +{
> + struct page *page = damon_phys_get_page(PHYS_PFN(paddr));
> + struct rmap_walk_control rwc = {
> + .rmap_one = damon_page_mkold,
> + .anon_lock = page_lock_anon_vma_read,
> + };
> + bool need_lock;
> +
> + if (!page)
> + return;
> +
> + if (!page_mapped(page) || !page_rmapping(page))
> + return;
I don't think you want to skip the unmapped pages. The point of
physical address space monitoring was to include the monitoring of
unmapped pages, so, skipping them invalidates the underlying
motivation.
> +
> + need_lock = !PageAnon(page) || PageKsm(page);
> + if (need_lock && !trylock_page(page))
> + return;
> +
> + rmap_walk(page, &rwc);
> +
> + if (need_lock)
> + unlock_page(page);
> + put_page(page);
> +}
> +
[snip]
> +
> +static bool damon_phys_young(unsigned long paddr, unsigned long *page_sz)
> +{
> + struct page *page = damon_phys_get_page(PHYS_PFN(paddr));
> + struct damon_phys_access_chk_result result = {
> + .page_sz = PAGE_SIZE,
> + .accessed = false,
> + };
> + struct rmap_walk_control rwc = {
> + .arg = &result,
> + .rmap_one = damon_page_accessed,
> + .anon_lock = page_lock_anon_vma_read,
> + };
> + bool need_lock;
> +
> + if (!page)
> + return false;
> +
> + if (!page_mapped(page) || !page_rmapping(page))
> + return false;
Same here.
> +
> + need_lock = !PageAnon(page) || PageKsm(page);
> + if (need_lock && !trylock_page(page))
> + return false;
> +
> + rmap_walk(page, &rwc);
> +
> + if (need_lock)
> + unlock_page(page);
> + put_page(page);
> +
> + *page_sz = result.page_sz;
> + return result.accessed;
> +}
> +
