From f995ea2ce5668aa736264c8044ce5bd986222afb Mon Sep 17 00:00:00 2001 From: Joao Martins Date: Tue, 13 Jul 2021 09:57:12 +0800 Subject: [PATCH] mm/gup: decrement head page once for group of subpages mainline inclusion from mainline-5.13-rc1 commit 31b912de1316644040ca9a0fb9b514ffa462c20c category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I408MI CVE: NA ------------------------------------------------- Rather than decrementing the head page refcount one by one, we walk the page array and checking which belong to the same compound_head. Later on we decrement the calculated amount of references in a single write to the head page. To that end switch to for_each_compound_head() does most of the work. set_page_dirty() needs no adjustment as it's a nop for non-dirty head pages and it doesn't operate on tail pages. This considerably improves unpinning of pages with THP and hugetlbfs: - THP gup_test -t -m 16384 -r 10 [-L|-a] -S -n 512 -w PIN_LONGTERM_BENCHMARK (put values): ~87.6k us -> ~23.2k us - 16G with 1G huge page size gup_test -f /mnt/huge/file -m 16384 -r 10 [-L|-a] -S -n 512 -w PIN_LONGTERM_BENCHMARK: (put values): ~87.6k us -> ~27.5k us Link: https://lkml.kernel.org/r/20210212130843.13865-3-joao.m.martins@oracle.com Signed-off-by: Joao Martins Reviewed-by: John Hubbard Reviewed-by: Jason Gunthorpe Cc: Christoph Hellwig Cc: Doug Ledford Cc: Matthew Wilcox Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Chengyang Fan Reviewed-by: Chen Wandun Signed-off-by: Zheng Zengkai --- mm/gup.c | 29 +++++++++++------------------ 1 file changed, 11 insertions(+), 18 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index 512bc2ca2138..015a55f79e55 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -266,20 +266,15 @@ void unpin_user_pages_dirty_lock(struct page **pages, unsigned long npages, bool make_dirty) { unsigned long index; - - /* - * TODO: this can be optimized for huge pages: if a series of pages is - * physically contiguous and part of the same compound page, then a - * single operation to the head page should suffice. - */ + struct page *head; + unsigned int ntails; if (!make_dirty) { unpin_user_pages(pages, npages); return; } - for (index = 0; index < npages; index++) { - struct page *page = compound_head(pages[index]); + for_each_compound_head(index, pages, npages, head, ntails) { /* * Checking PageDirty at this point may race with * clear_page_dirty_for_io(), but that's OK. Two key @@ -300,9 +295,9 @@ void unpin_user_pages_dirty_lock(struct page **pages, unsigned long npages, * written back, so it gets written back again in the * next writeback cycle. This is harmless. */ - if (!PageDirty(page)) - set_page_dirty_lock(page); - unpin_user_page(page); + if (!PageDirty(head)) + set_page_dirty_lock(head); + put_compound_head(head, ntails, FOLL_PIN); } } EXPORT_SYMBOL(unpin_user_pages_dirty_lock); @@ -319,6 +314,8 @@ EXPORT_SYMBOL(unpin_user_pages_dirty_lock); void unpin_user_pages(struct page **pages, unsigned long npages) { unsigned long index; + struct page *head; + unsigned int ntails; /* * If this WARN_ON() fires, then the system *might* be leaking pages (by @@ -327,13 +324,9 @@ void unpin_user_pages(struct page **pages, unsigned long npages) */ if (WARN_ON(IS_ERR_VALUE(npages))) return; - /* - * TODO: this can be optimized for huge pages: if a series of pages is - * physically contiguous and part of the same compound page, then a - * single operation to the head page should suffice. - */ - for (index = 0; index < npages; index++) - unpin_user_page(pages[index]); + + for_each_compound_head(index, pages, npages, head, ntails) + put_compound_head(head, ntails, FOLL_PIN); } EXPORT_SYMBOL(unpin_user_pages); -- GitLab