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    SubjectRe: [PATCH v3 2/9] mm/vmscan: protect the workingset on anonymous LRU
    On Tue, Mar 17, 2020 at 02:41:50PM +0900, js1304@gmail.com wrote:
    > From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
    >
    > In current implementation, newly created or swap-in anonymous page
    > is started on active list. Growing active list results in rebalancing
    > active/inactive list so old pages on active list are demoted to inactive
    > list. Hence, the page on active list isn't protected at all.
    >
    > Following is an example of this situation.
    >
    > Assume that 50 hot pages on active list. Numbers denote the number of
    > pages on active/inactive list (active | inactive).
    >
    > 1. 50 hot pages on active list
    > 50(h) | 0
    >
    > 2. workload: 50 newly created (used-once) pages
    > 50(uo) | 50(h)
    >
    > 3. workload: another 50 newly created (used-once) pages
    > 50(uo) | 50(uo), swap-out 50(h)
    >
    > This patch tries to fix this issue.
    > Like as file LRU, newly created or swap-in anonymous pages will be
    > inserted to the inactive list. They are promoted to active list if
    > enough reference happens. This simple modification changes the above
    > example as following.
    >
    > 1. 50 hot pages on active list
    > 50(h) | 0
    >
    > 2. workload: 50 newly created (used-once) pages
    > 50(h) | 50(uo)
    >
    > 3. workload: another 50 newly created (used-once) pages
    > 50(h) | 50(uo), swap-out 50(uo)
    >
    > As you can see, hot pages on active list would be protected.
    >
    > Note that, this implementation has a drawback that the page cannot
    > be promoted and will be swapped-out if re-access interval is greater than
    > the size of inactive list but less than the size of total(active+inactive).
    > To solve this potential issue, following patch will apply workingset
    > detection that is applied to file LRU some day before.
    >
    > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>

    Acked-by: Johannes Weiner <hannes@cmpxchg.org>

    > -void lru_cache_add_active_or_unevictable(struct page *page,
    > +void lru_cache_add_inactive_or_unevictable(struct page *page,
    > struct vm_area_struct *vma)
    > {
    > + bool evictable;
    > +
    > VM_BUG_ON_PAGE(PageLRU(page), page);
    >
    > - if (likely((vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) != VM_LOCKED))
    > - SetPageActive(page);
    > - else if (!TestSetPageMlocked(page)) {
    > + evictable = (vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) != VM_LOCKED;
    > + if (!evictable && !TestSetPageMlocked(page)) {

    Minor point, but in case there is a v4: `unevictable` instead of
    !evictable would be a bit easier to read, match the function name,
    PageUnevictable etc.

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