From 1970dc6f5226416957ad0cc70ab47386ed3195a6 Mon Sep 17 00:00:00 2001 From: John Hubbard Date: Wed, 1 Apr 2020 21:05:37 -0700 Subject: mm/gup: /proc/vmstat: pin_user_pages (FOLL_PIN) reporting MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Now that pages are "DMA-pinned" via pin_user_page*(), and unpinned via unpin_user_pages*(), we need some visibility into whether all of this is working correctly. Add two new fields to /proc/vmstat: nr_foll_pin_acquired nr_foll_pin_released These are documented in Documentation/core-api/pin_user_pages.rst. They represent the number of pages (since boot time) that have been pinned ("nr_foll_pin_acquired") and unpinned ("nr_foll_pin_released"), via pin_user_pages*() and unpin_user_pages*(). In the absence of long-running DMA or RDMA operations that hold pages pinned, the above two fields will normally be equal to each other. Also: update Documentation/core-api/pin_user_pages.rst, to remove an earlier (now confirmed untrue) claim about a performance problem with /proc/vmstat. Also: update Documentation/core-api/pin_user_pages.rst to rename the new /proc/vmstat entries, to the names listed here. Signed-off-by: John Hubbard Signed-off-by: Andrew Morton Reviewed-by: Jan Kara Acked-by: Kirill A. Shutemov Cc: Ira Weiny Cc: Jérôme Glisse Cc: "Matthew Wilcox (Oracle)" Cc: Al Viro Cc: Christoph Hellwig Cc: Dan Williams Cc: Dave Chinner Cc: Jason Gunthorpe Cc: Jonathan Corbet Cc: Michal Hocko Cc: Mike Kravetz Cc: Shuah Khan Cc: Vlastimil Babka Link: http://lkml.kernel.org/r/20200211001536.1027652-9-jhubbard@nvidia.com Signed-off-by: Linus Torvalds --- mm/gup.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'mm/gup.c') diff --git a/mm/gup.c b/mm/gup.c index 6601df4c7682..c560c9cc0ee5 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -86,6 +86,8 @@ static __maybe_unused struct page *try_grab_compound_head(struct page *page, if (flags & FOLL_GET) return try_get_compound_head(page, refs); else if (flags & FOLL_PIN) { + int orig_refs = refs; + /* * When pinning a compound page of order > 1 (which is what * hpage_pincount_available() checks for), use an exact count to @@ -104,6 +106,9 @@ static __maybe_unused struct page *try_grab_compound_head(struct page *page, if (hpage_pincount_available(page)) hpage_pincount_add(page, refs); + mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_ACQUIRED, + orig_refs); + return page; } @@ -158,6 +163,8 @@ bool __must_check try_grab_page(struct page *page, unsigned int flags) * once, so that the page really is pinned. */ page_ref_add(page, refs); + + mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_ACQUIRED, 1); } return true; @@ -178,6 +185,7 @@ static bool __unpin_devmap_managed_user_page(struct page *page) count = page_ref_sub_return(page, refs); + mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_RELEASED, 1); /* * devmap page refcounts are 1-based, rather than 0-based: if * refcount is 1, then the page is free and the refcount is @@ -228,6 +236,8 @@ void unpin_user_page(struct page *page) if (page_ref_sub_and_test(page, refs)) __put_page(page); + + mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_RELEASED, 1); } EXPORT_SYMBOL(unpin_user_page); @@ -2014,6 +2024,9 @@ EXPORT_SYMBOL(get_user_pages_unlocked); static void put_compound_head(struct page *page, int refs, unsigned int flags) { if (flags & FOLL_PIN) { + mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_RELEASED, + refs); + if (hpage_pincount_available(page)) hpage_pincount_sub(page, refs); else -- cgit v1.2.3