Pages in pagevec may have different lruvec, so we have to do relock in function pagevec_lru_move_fn(), but a relock may cause current cpu wait for long time on the same lock for spinlock fairness reason.
Before per memcg lru_lock, we have to bear the relock since the spinlock is the only way to serialize page's memcg/lruvec. Now TestClearPageLRU could be used to isolate pages exculsively, and stable the page's lruvec/memcg. So it gives us a chance to sort the page's lruvec before moving action in pagevec_lru_move_fn. Then we don't suffer from the spinlock's fairness wait. Signed-off-by: Alex Shi <alex....@linux.alibaba.com> Cc: Konstantin Khlebnikov <koc...@gmail.com> Cc: Hugh Dickins <hu...@google.com> Cc: Yu Zhao <yuz...@google.com> Cc: Michal Hocko <mho...@suse.com> Cc: Matthew Wilcox (Oracle) <wi...@infradead.org> Cc: Andrew Morton <a...@linux-foundation.org> Cc: linux...@kvack.org Cc: linux-kernel@vger.kernel.org --- mm/swap.c | 92 +++++++++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 79 insertions(+), 13 deletions(-) diff --git a/mm/swap.c b/mm/swap.c index c5363bdebe67..994641331bf7 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -201,29 +201,95 @@ int get_kernel_page(unsigned long start, int write, struct page **pages) } EXPORT_SYMBOL_GPL(get_kernel_page); +/* Pratt's gaps for shell sort, https://en.wikipedia.org/wiki/Shellsort */ +static int gaps[] = { 6, 4, 3, 2, 1, 0}; + +/* Shell sort pagevec[] on page's lruvec.*/ +static void shell_sort(struct pagevec *pvec, unsigned long *lvaddr) +{ + int g, i, j, n = pagevec_count(pvec); + + for (g=0; gaps[g] > 0 && gaps[g] <= n/2; g++) { + int gap = gaps[g]; + + for (i = gap; i < n; i++) { + unsigned long tmp = lvaddr[i]; + struct page *page = pvec->pages[i]; + + for (j = i - gap; j >= 0 && lvaddr[j] > tmp; j -= gap) { + lvaddr[j + gap] = lvaddr[j]; + pvec->pages[j + gap] = pvec->pages[j]; + } + lvaddr[j + gap] = tmp; + pvec->pages[j + gap] = page; + } + } +} + +/* Get lru bit cleared page and their lruvec address, release the others */ +void sort_isopv(struct pagevec *pvec, struct pagevec *isopv, + unsigned long *lvaddr) +{ + int i, j; + struct pagevec busypv; + + pagevec_init(&busypv); + + for (i = 0, j = 0; i < pagevec_count(pvec); i++) { + struct page *page = pvec->pages[i]; + + pvec->pages[i] = NULL; + + /* block memcg migration during page moving between lru */ + if (!TestClearPageLRU(page)) { + pagevec_add(&busypv, page); + continue; + } + lvaddr[j++] = (unsigned long) + mem_cgroup_page_lruvec(page, page_pgdat(page)); + pagevec_add(isopv, page); + } + pagevec_reinit(pvec); + if (pagevec_count(&busypv)) + release_pages(busypv.pages, busypv.nr); + + shell_sort(isopv, lvaddr); +} + static void pagevec_lru_move_fn(struct pagevec *pvec, void (*move_fn)(struct page *page, struct lruvec *lruvec)) { - int i; + int i, n; struct lruvec *lruvec = NULL; unsigned long flags = 0; + unsigned long lvaddr[PAGEVEC_SIZE]; + struct pagevec isopv; - for (i = 0; i < pagevec_count(pvec); i++) { - struct page *page = pvec->pages[i]; + pagevec_init(&isopv); - /* block memcg migration during page moving between lru */ - if (!TestClearPageLRU(page)) - continue; + sort_isopv(pvec, &isopv, lvaddr); - lruvec = relock_page_lruvec_irqsave(page, lruvec, &flags); - (*move_fn)(page, lruvec); + n = pagevec_count(&isopv); + if (!n) + return; - SetPageLRU(page); + lruvec = (struct lruvec *)lvaddr[0]; + spin_lock_irqsave(&lruvec->lru_lock, flags); + + for (i = 0; i < n; i++) { + /* lock new lruvec if lruvec changes, we have sorted them */ + if (lruvec != (struct lruvec *)lvaddr[i]) { + spin_unlock_irqrestore(&lruvec->lru_lock, flags); + lruvec = (struct lruvec *)lvaddr[i]; + spin_lock_irqsave(&lruvec->lru_lock, flags); + } + + (*move_fn)(isopv.pages[i], lruvec); + + SetPageLRU(isopv.pages[i]); } - if (lruvec) - unlock_page_lruvec_irqrestore(lruvec, flags); - release_pages(pvec->pages, pvec->nr); - pagevec_reinit(pvec); + spin_unlock_irqrestore(&lruvec->lru_lock, flags); + release_pages(isopv.pages, isopv.nr); } static void pagevec_move_tail_fn(struct page *page, struct lruvec *lruvec) -- 2.29.GIT
