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708a507af0
Refresh kernel patches for generic kernel 5.15 due to new backport version of MGLRU patchset. Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
125 lines
4.3 KiB
Diff
125 lines
4.3 KiB
Diff
From 6f315879ad750391a0b1fab8c9170bc054a5f5d7 Mon Sep 17 00:00:00 2001
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From: Yu Zhao <yuzhao@google.com>
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Date: Tue, 15 Nov 2022 18:38:07 -0700
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Subject: [PATCH 14/29] mm: multi-gen LRU: retry pages written back while
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isolated
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The page reclaim isolates a batch of pages from the tail of one of the
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LRU lists and works on those pages one by one. For a suitable
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swap-backed page, if the swap device is async, it queues that page for
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writeback. After the page reclaim finishes an entire batch, it puts back
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the pages it queued for writeback to the head of the original LRU list.
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In the meantime, the page writeback flushes the queued pages also by
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batches. Its batching logic is independent from that of the page reclaim.
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For each of the pages it writes back, the page writeback calls
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rotate_reclaimable_page() which tries to rotate a page to the tail.
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rotate_reclaimable_page() only works for a page after the page reclaim
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has put it back. If an async swap device is fast enough, the page
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writeback can finish with that page while the page reclaim is still
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working on the rest of the batch containing it. In this case, that page
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will remain at the head and the page reclaim will not retry it before
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reaching there.
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This patch adds a retry to evict_pages(). After evict_pages() has
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finished an entire batch and before it puts back pages it cannot free
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immediately, it retries those that may have missed the rotation.
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Before this patch, ~60% of pages swapped to an Intel Optane missed
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rotate_reclaimable_page(). After this patch, ~99% of missed pages were
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reclaimed upon retry.
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This problem affects relatively slow async swap devices like Samsung 980
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Pro much less and does not affect sync swap devices like zram or zswap at
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all.
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Link: https://lkml.kernel.org/r/20221116013808.3995280-1-yuzhao@google.com
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Fixes: ac35a4902374 ("mm: multi-gen LRU: minimal implementation")
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Signed-off-by: Yu Zhao <yuzhao@google.com>
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Cc: "Yin, Fengwei" <fengwei.yin@intel.com>
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Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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---
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mm/vmscan.c | 48 +++++++++++++++++++++++++++++++++++++-----------
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1 file changed, 37 insertions(+), 11 deletions(-)
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--- a/mm/vmscan.c
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+++ b/mm/vmscan.c
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@@ -4723,10 +4723,13 @@ static int evict_pages(struct lruvec *lr
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int scanned;
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int reclaimed;
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LIST_HEAD(list);
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+ LIST_HEAD(clean);
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struct page *page;
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+ struct page *next;
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enum vm_event_item item;
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struct reclaim_stat stat;
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struct lru_gen_mm_walk *walk;
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+ bool skip_retry = false;
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struct mem_cgroup *memcg = lruvec_memcg(lruvec);
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struct pglist_data *pgdat = lruvec_pgdat(lruvec);
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@@ -4743,20 +4746,37 @@ static int evict_pages(struct lruvec *lr
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if (list_empty(&list))
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return scanned;
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-
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+retry:
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reclaimed = shrink_page_list(&list, pgdat, sc, &stat, false);
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+ sc->nr_reclaimed += reclaimed;
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- list_for_each_entry(page, &list, lru) {
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- /* restore LRU_REFS_FLAGS cleared by isolate_page() */
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- if (PageWorkingset(page))
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- SetPageReferenced(page);
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+ list_for_each_entry_safe_reverse(page, next, &list, lru) {
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+ if (!page_evictable(page)) {
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+ list_del(&page->lru);
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+ putback_lru_page(page);
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+ continue;
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+ }
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- /* don't add rejected pages to the oldest generation */
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if (PageReclaim(page) &&
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- (PageDirty(page) || PageWriteback(page)))
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- ClearPageActive(page);
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- else
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- SetPageActive(page);
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+ (PageDirty(page) || PageWriteback(page))) {
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+ /* restore LRU_REFS_FLAGS cleared by isolate_page() */
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+ if (PageWorkingset(page))
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+ SetPageReferenced(page);
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+ continue;
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+ }
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+
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+ if (skip_retry || PageActive(page) || PageReferenced(page) ||
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+ page_mapped(page) || PageLocked(page) ||
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+ PageDirty(page) || PageWriteback(page)) {
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+ /* don't add rejected pages to the oldest generation */
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+ set_mask_bits(&page->flags, LRU_REFS_MASK | LRU_REFS_FLAGS,
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+ BIT(PG_active));
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+ continue;
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+ }
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+
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+ /* retry pages that may have missed rotate_reclaimable_page() */
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+ list_move(&page->lru, &clean);
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+ sc->nr_scanned -= thp_nr_pages(page);
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}
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spin_lock_irq(&lruvec->lru_lock);
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@@ -4778,7 +4798,13 @@ static int evict_pages(struct lruvec *lr
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mem_cgroup_uncharge_list(&list);
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free_unref_page_list(&list);
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- sc->nr_reclaimed += reclaimed;
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+ INIT_LIST_HEAD(&list);
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+ list_splice_init(&clean, &list);
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+
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+ if (!list_empty(&list)) {
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+ skip_retry = true;
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+ goto retry;
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+ }
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if (need_swapping && type == LRU_GEN_ANON)
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*need_swapping = true;
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