The patch titled
Subject: mm/swap.c: reduce lock contention in lru_cache_add
has been added to the -mm tree. Its filename is
mm-swapc-reduce-lock-contention-in-lru_cache_add.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-swapc-reduce-lock-contention-in-lru_cache_add.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-swapc-reduce-lock-contention-in-lru_cache_add.patch
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------------------------------------------------------
From: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx>
Subject: mm/swap.c: reduce lock contention in lru_cache_add
The current relock logic will change lru_lock when it finds a new lruvec,
so if 2 memcgs are reading a file or allocating pages at same time, they
could hold the lru_lock alternately, and wait for each other for fairness
attribute of ticket spin lock.
This patch will sort all lru_locks and only hold them once in the above
scenario. That could reduce fairness waiting for lock reacquision.
vm-scalability/case-lru-file-readtwice gets a ~5% performance gain on my
2P*20core*HT machine.
Testing when all or most of the pages belong to the same lruvec show no
regression - most time is spent on lru_lock for lru sensitive cases.
Link: https://lkml.kernel.org/r/1605860847-47445-1-git-send-email-alex.shi@xxxxxxxxxxxxxxxxx
Suggested-by: Konstantin Khlebnikov <koct9i@xxxxxxxxx>
Signed-off-by: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx>
Cc: Konstantin Khlebnikov <koct9i@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/swap.c | 57 ++++++++++++++++++++++++++++++++++++++++++++--------
1 file changed, 49 insertions(+), 8 deletions(-)
--- a/mm/swap.c~mm-swapc-reduce-lock-contention-in-lru_cache_add
+++ a/mm/swap.c
@@ -1009,24 +1009,65 @@ static void __pagevec_lru_add_fn(struct
trace_mm_lru_insertion(page, lru);
}
+struct lruvecs {
+ struct list_head lists[PAGEVEC_SIZE];
+ struct lruvec *vecs[PAGEVEC_SIZE];
+};
+
+/* Sort pvec pages on their lruvec */
+int sort_page_lruvec(struct lruvecs *lruvecs, struct pagevec *pvec)
+{
+ int i, j, nr_lruvec;
+ struct page *page;
+ struct lruvec *lruvec = NULL;
+
+ lruvecs->vecs[0] = NULL;
+ for (i = nr_lruvec = 0; i < pagevec_count(pvec); i++) {
+ page = pvec->pages[i];
+ lruvec = mem_cgroup_page_lruvec(page, page_pgdat(page));
+
+ /* Try to find a same lruvec */
+ for (j = 0; j <= nr_lruvec; j++)
+ if (lruvec == lruvecs->vecs[j])
+ break;
+
+ /* A new lruvec */
+ if (j > nr_lruvec) {
+ INIT_LIST_HEAD(&lruvecs->lists[nr_lruvec]);
+ lruvecs->vecs[nr_lruvec] = lruvec;
+ j = nr_lruvec++;
+ lruvecs->vecs[nr_lruvec] = 0;
+ }
+
+ list_add_tail(&page->lru, &lruvecs->lists[j]);
+ }
+
+ return nr_lruvec;
+}
+
/*
* Add the passed pages to the LRU, then drop the caller's refcount
* on them. Reinitialises the caller's pagevec.
*/
void __pagevec_lru_add(struct pagevec *pvec)
{
- int i;
- struct lruvec *lruvec = NULL;
+ int i, nr_lruvec;
unsigned long flags = 0;
+ struct page *page;
+ struct lruvecs lruvecs;
- for (i = 0; i < pagevec_count(pvec); i++) {
- struct page *page = pvec->pages[i];
+ nr_lruvec = sort_page_lruvec(&lruvecs, pvec);
- lruvec = relock_page_lruvec_irqsave(page, lruvec, &flags);
- __pagevec_lru_add_fn(page, lruvec);
+ for (i = 0; i < nr_lruvec; i++) {
+ spin_lock_irqsave(&lruvecs.vecs[i]->lru_lock, flags);
+ while (!list_empty(&lruvecs.lists[i])) {
+ page = lru_to_page(&lruvecs.lists[i]);
+ list_del(&page->lru);
+ __pagevec_lru_add_fn(page, lruvecs.vecs[i]);
+ }
+ spin_unlock_irqrestore(&lruvecs.vecs[i]->lru_lock, flags);
}
- if (lruvec)
- unlock_page_lruvec_irqrestore(lruvec, flags);
+
release_pages(pvec->pages, pvec->nr);
pagevec_reinit(pvec);
}
_
Patches currently in -mm which might be from alex.shi@xxxxxxxxxxxxxxxxx are
mm-filemap-add-static-for-function-__add_to_page_cache_locked.patch
fs-ntfs-remove-unused-varibles.patch
fs-ntfs-remove-unused-varible-attr_len.patch
mm-truncate-add-parameter-explanation-for-invalidate_mapping_pagevec.patch
mm-memcg-update-page-struct-member-in-comments.patch
mm-thp-move-lru_add_page_tail-func-to-huge_memoryc.patch
mm-thp-use-head-for-head-page-in-lru_add_page_tail.patch
mm-thp-simplify-lru_add_page_tail.patch
mm-thp-narrow-lru-locking.patch
mm-vmscan-remove-unnecessary-lruvec-adding.patch
mm-rmap-stop-store-reordering-issue-on-page-mapping.patch
mm-rmap-stop-store-reordering-issue-on-page-mapping-fix.patch
mm-memcg-add-debug-checking-in-lock_page_memcg.patch
mm-swapc-fold-vm-event-pgrotated-into-pagevec_move_tail_fn.patch
mm-lru-move-lock-into-lru_note_cost.patch
mm-vmscan-remove-lruvec-reget-in-move_pages_to_lru.patch
mm-mlock-remove-lru_lock-on-testclearpagemlocked.patch
mm-mlock-remove-__munlock_isolate_lru_page.patch
mm-lru-introduce-testclearpagelru.patch
mm-compaction-do-page-isolation-first-in-compaction.patch
mm-swapc-serialize-memcg-changes-in-pagevec_lru_move_fn.patch
mm-lru-replace-pgdat-lru_lock-with-lruvec-lock.patch
mm-lru-replace-pgdat-lru_lock-with-lruvec-lock-fix.patch
mm-lru-replace-pgdat-lru_lock-with-lruvec-lock-fix-2.patch
mm-lru-introduce-the-relock_page_lruvec-function-fix.patch
mm-memcg-remove-incorrect-comments.patch
mm-mapping_dirty_helpers-enhance-the-kernel-doc-markups.patch
mm-add-colon-to-fix-kernel-doc-markups-error-for-check_pte.patch
mm-vmalloc-add-align-parameter-explanation-for-pvm_determine_end_from_reverse.patch
docs-vm-remove-unused-3-items-explanation-for-proc-vmstat.patch
khugepaged-add-couples-parameter-explanation-for-kernel-doc-markup.patch
gcov-fix-kernel-doc-markup-issue.patch
mm-swapc-reduce-lock-contention-in-lru_cache_add.patch
mm-memcg-bail-early-from-swap-accounting-if-memcg-disabled.patch
mm-memcg-warning-on-memcg-after-readahead-page-charged.patch
mm-memcontrol-rewrite-mem_cgroup_page_lruvec-fix.patch
