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By doing this we should be able to reduce the overhead and can consolidate all of the list addition bits in one spot. Acked-by: David Hildenbrand Reviewed-by: Dan Williams Signed-off-by: Alexander Duyck --- include/linux/mmzone.h | 12 -------- mm/page_alloc.c | 71 ++++++++++++++++++++++++++++-------------------- mm/shuffle.c | 12 ++++---- mm/shuffle.h | 6 ++++ 4 files changed, 54 insertions(+), 47 deletions(-) diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 89d8ff06c9ce..245010b24747 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -116,18 +116,6 @@ static inline void add_to_free_area_tail(struct page *page, struct free_area *ar area->nr_free++; } -#ifdef CONFIG_SHUFFLE_PAGE_ALLOCATOR -/* Used to preserve page allocation order entropy */ -void add_to_free_area_random(struct page *page, struct free_area *area, - int migratetype); -#else -static inline void add_to_free_area_random(struct page *page, - struct free_area *area, int migratetype) -{ - add_to_free_area(page, area, migratetype); -} -#endif - /* Used for pages which are on another list */ static inline void move_to_free_area(struct page *page, struct free_area *area, int migratetype) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 62dcd6b76c80..32e9cc092656 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -878,6 +878,36 @@ static inline struct capture_control *task_capc(struct zone *zone) #endif /* CONFIG_COMPACTION */ /* + * If this is not the largest possible page, check if the buddy + * of the next-highest order is free. If it is, it's possible + * that pages are being freed that will coalesce soon. In case, + * that is happening, add the free page to the tail of the list + * so it's less likely to be used soon and more likely to be merged + * as a higher order page + */ +static inline bool +buddy_merge_likely(unsigned long pfn, unsigned long buddy_pfn, + struct page *page, unsigned int order) +{ + struct page *higher_page, *higher_buddy; + unsigned long combined_pfn; + + if (order >= MAX_ORDER - 2) + return false; + + if (!pfn_valid_within(buddy_pfn)) + return false; + + combined_pfn = buddy_pfn & pfn; + higher_page = page + (combined_pfn - pfn); + buddy_pfn = __find_buddy_pfn(combined_pfn, order + 1); + higher_buddy = higher_page + (buddy_pfn - combined_pfn); + + return pfn_valid_within(buddy_pfn) && + page_is_buddy(higher_page, higher_buddy, order + 1); +} + +/* * Freeing function for a buddy system allocator. * * The concept of a buddy system is to maintain direct-mapped table @@ -906,11 +936,13 @@ static inline void __free_one_page(struct page *page, struct zone *zone, unsigned int order, int migratetype) { - unsigned long combined_pfn; + struct capture_control *capc = task_capc(zone); unsigned long uninitialized_var(buddy_pfn); - struct page *buddy; + unsigned long combined_pfn; + struct free_area *area; unsigned int max_order; - struct capture_control *capc = task_capc(zone); + struct page *buddy; + bool to_tail; max_order = min_t(unsigned int, MAX_ORDER, pageblock_order + 1); @@ -979,35 +1011,16 @@ static inline void __free_one_page(struct page *page, done_merging: set_page_order(page, order); - /* - * If this is not the largest possible page, check if the buddy - * of the next-highest order is free. If it is, it's possible - * that pages are being freed that will coalesce soon. In case, - * that is happening, add the free page to the tail of the list - * so it's less likely to be used soon and more likely to be merged - * as a higher order page - */ - if ((order < MAX_ORDER-2) && pfn_valid_within(buddy_pfn) - && !is_shuffle_order(order)) { - struct page *higher_page, *higher_buddy; - combined_pfn = buddy_pfn & pfn; - higher_page = page + (combined_pfn - pfn); - buddy_pfn = __find_buddy_pfn(combined_pfn, order + 1); - higher_buddy = higher_page + (buddy_pfn - combined_pfn); - if (pfn_valid_within(buddy_pfn) && - page_is_buddy(higher_page, higher_buddy, order + 1)) { - add_to_free_area_tail(page, &zone->free_area[order], - migratetype); - return; - } - } - + area = &zone->free_area[order]; if (is_shuffle_order(order)) - add_to_free_area_random(page, &zone->free_area[order], - migratetype); + to_tail = shuffle_pick_tail(); else - add_to_free_area(page, &zone->free_area[order], migratetype); + to_tail = buddy_merge_likely(pfn, buddy_pfn, page, order); + if (to_tail) + add_to_free_area_tail(page, area, migratetype); + else + add_to_free_area(page, area, migratetype); } /* diff --git a/mm/shuffle.c b/mm/shuffle.c index b3fe97fd6654..e65d57f39486 100644 --- a/mm/shuffle.c +++ b/mm/shuffle.c @@ -183,11 +183,11 @@ void __meminit __shuffle_free_memory(pg_data_t *pgdat) shuffle_zone(z); } -void add_to_free_area_random(struct page *page, struct free_area *area, - int migratetype) +bool shuffle_pick_tail(void) { static u64 rand; static u8 rand_bits; + bool ret; /* * The lack of locking is deliberate. If 2 threads race to @@ -198,10 +198,10 @@ void add_to_free_area_random(struct page *page, struct free_area *area, rand = get_random_u64(); } - if (rand & 1) - add_to_free_area(page, area, migratetype); - else - add_to_free_area_tail(page, area, migratetype); + ret = rand & 1; + rand_bits--; rand >>= 1; + + return ret; } diff --git a/mm/shuffle.h b/mm/shuffle.h index 777a257a0d2f..4d79f03b6658 100644 --- a/mm/shuffle.h +++ b/mm/shuffle.h @@ -22,6 +22,7 @@ enum mm_shuffle_ctl { DECLARE_STATIC_KEY_FALSE(page_alloc_shuffle_key); extern void page_alloc_shuffle(enum mm_shuffle_ctl ctl); extern void __shuffle_free_memory(pg_data_t *pgdat); +extern bool shuffle_pick_tail(void); static inline void shuffle_free_memory(pg_data_t *pgdat) { if (!static_branch_unlikely(&page_alloc_shuffle_key)) @@ -44,6 +45,11 @@ static inline bool is_shuffle_order(int order) return order >= SHUFFLE_ORDER; } #else +static inline bool shuffle_pick_tail(void) +{ + return false; +} + static inline void shuffle_free_memory(pg_data_t *pgdat) { } From patchwork Thu Dec 5 16:22:21 2019 Content-Type: text/plain; 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As it turns out most of the accessors were always just being directly passed &zone->free_area[order] anyway so it would make sense to just fold that into the function itself and pass the zone and order as arguments instead of the free area. In order to be able to reference the zone we need to move the declaration of the functions down so that we have the zone defined before we define the list manipulation functions. Since the functions are only used in the file mm/page_alloc.c we can just move them there to reduce noise in the header. Reviewed-by: Dan Williams Reviewed-by: David Hildenbrand Reviewed-by: Pankaj Gupta Signed-off-by: Alexander Duyck --- include/linux/mmzone.h | 32 ----------------------- mm/page_alloc.c | 67 +++++++++++++++++++++++++++++++++++------------- 2 files changed, 49 insertions(+), 50 deletions(-) diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 245010b24747..8d93106490f3 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -100,29 +100,6 @@ struct free_area { unsigned long nr_free; }; -/* Used for pages not on another list */ -static inline void add_to_free_area(struct page *page, struct free_area *area, - int migratetype) -{ - list_add(&page->lru, &area->free_list[migratetype]); - area->nr_free++; -} - -/* Used for pages not on another list */ -static inline void add_to_free_area_tail(struct page *page, struct free_area *area, - int migratetype) -{ - list_add_tail(&page->lru, &area->free_list[migratetype]); - area->nr_free++; -} - -/* Used for pages which are on another list */ -static inline void move_to_free_area(struct page *page, struct free_area *area, - int migratetype) -{ - list_move(&page->lru, &area->free_list[migratetype]); -} - static inline struct page *get_page_from_free_area(struct free_area *area, int migratetype) { @@ -130,15 +107,6 @@ static inline struct page *get_page_from_free_area(struct free_area *area, struct page, lru); } -static inline void del_page_from_free_area(struct page *page, - struct free_area *area) -{ - list_del(&page->lru); - __ClearPageBuddy(page); - set_page_private(page, 0); - area->nr_free--; -} - static inline bool free_area_empty(struct free_area *area, int migratetype) { return list_empty(&area->free_list[migratetype]); diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 32e9cc092656..e0a7895300fb 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -877,6 +877,44 @@ static inline struct capture_control *task_capc(struct zone *zone) } #endif /* CONFIG_COMPACTION */ +/* Used for pages not on another list */ +static inline void add_to_free_list(struct page *page, struct zone *zone, + unsigned int order, int migratetype) +{ + struct free_area *area = &zone->free_area[order]; + + list_add(&page->lru, &area->free_list[migratetype]); + area->nr_free++; +} + +/* Used for pages not on another list */ +static inline void add_to_free_list_tail(struct page *page, struct zone *zone, + unsigned int order, int migratetype) +{ + struct free_area *area = &zone->free_area[order]; + + list_add_tail(&page->lru, &area->free_list[migratetype]); + area->nr_free++; +} + +/* Used for pages which are on another list */ +static inline void move_to_free_list(struct page *page, struct zone *zone, + unsigned int order, int migratetype) +{ + struct free_area *area = &zone->free_area[order]; + + list_move(&page->lru, &area->free_list[migratetype]); +} + +static inline void del_page_from_free_list(struct page *page, struct zone *zone, + unsigned int order) +{ + list_del(&page->lru); + __ClearPageBuddy(page); + set_page_private(page, 0); + zone->free_area[order].nr_free--; +} + /* * If this is not the largest possible page, check if the buddy * of the next-highest order is free. If it is, it's possible @@ -939,7 +977,6 @@ static inline void __free_one_page(struct page *page, struct capture_control *capc = task_capc(zone); unsigned long uninitialized_var(buddy_pfn); unsigned long combined_pfn; - struct free_area *area; unsigned int max_order; struct page *buddy; bool to_tail; @@ -977,7 +1014,7 @@ static inline void __free_one_page(struct page *page, if (page_is_guard(buddy)) clear_page_guard(zone, buddy, order, migratetype); else - del_page_from_free_area(buddy, &zone->free_area[order]); + del_page_from_free_list(buddy, zone, order); combined_pfn = buddy_pfn & pfn; page = page + (combined_pfn - pfn); pfn = combined_pfn; @@ -1011,16 +1048,15 @@ static inline void __free_one_page(struct page *page, done_merging: set_page_order(page, order); - area = &zone->free_area[order]; if (is_shuffle_order(order)) to_tail = shuffle_pick_tail(); else to_tail = buddy_merge_likely(pfn, buddy_pfn, page, order); if (to_tail) - add_to_free_area_tail(page, area, migratetype); + add_to_free_list_tail(page, zone, order, migratetype); else - add_to_free_area(page, area, migratetype); + add_to_free_list(page, zone, order, migratetype); } /* @@ -2038,13 +2074,11 @@ void __init init_cma_reserved_pageblock(struct page *page) * -- nyc */ static inline void expand(struct zone *zone, struct page *page, - int low, int high, struct free_area *area, - int migratetype) + int low, int high, int migratetype) { unsigned long size = 1 << high; while (high > low) { - area--; high--; size >>= 1; VM_BUG_ON_PAGE(bad_range(zone, &page[size]), &page[size]); @@ -2058,7 +2092,7 @@ static inline void expand(struct zone *zone, struct page *page, if (set_page_guard(zone, &page[size], high, migratetype)) continue; - add_to_free_area(&page[size], area, migratetype); + add_to_free_list(&page[size], zone, high, migratetype); set_page_order(&page[size], high); } } @@ -2216,8 +2250,8 @@ struct page *__rmqueue_smallest(struct zone *zone, unsigned int order, page = get_page_from_free_area(area, migratetype); if (!page) continue; - del_page_from_free_area(page, area); - expand(zone, page, order, current_order, area, migratetype); + del_page_from_free_list(page, zone, current_order); + expand(zone, page, order, current_order, migratetype); set_pcppage_migratetype(page, migratetype); return page; } @@ -2291,7 +2325,7 @@ static int move_freepages(struct zone *zone, VM_BUG_ON_PAGE(page_zone(page) != zone, page); order = page_order(page); - move_to_free_area(page, &zone->free_area[order], migratetype); + move_to_free_list(page, zone, order, migratetype); page += 1 << order; pages_moved += 1 << order; } @@ -2407,7 +2441,6 @@ static void steal_suitable_fallback(struct zone *zone, struct page *page, unsigned int alloc_flags, int start_type, bool whole_block) { unsigned int current_order = page_order(page); - struct free_area *area; int free_pages, movable_pages, alike_pages; int old_block_type; @@ -2478,8 +2511,7 @@ static void steal_suitable_fallback(struct zone *zone, struct page *page, return; single_page: - area = &zone->free_area[current_order]; - move_to_free_area(page, area, start_type); + move_to_free_list(page, zone, current_order, start_type); } /* @@ -3150,7 +3182,6 @@ void split_page(struct page *page, unsigned int order) int __isolate_free_page(struct page *page, unsigned int order) { - struct free_area *area = &page_zone(page)->free_area[order]; unsigned long watermark; struct zone *zone; int mt; @@ -3176,7 +3207,7 @@ int __isolate_free_page(struct page *page, unsigned int order) /* Remove page from free list */ - del_page_from_free_area(page, area); + del_page_from_free_list(page, zone, order); /* * Set the pageblock if the isolated page is at least half of a @@ -8703,7 +8734,7 @@ void zone_pcp_reset(struct zone *zone) pr_info("remove from free list %lx %d %lx\n", pfn, 1 << order, end_pfn); #endif - del_page_from_free_area(page, &zone->free_area[order]); + del_page_from_free_list(page, zone, order); pfn += (1 << order); } spin_unlock_irqrestore(&zone->lock, flags); From patchwork Thu Dec 5 16:22:30 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Duyck X-Patchwork-Id: 11275161 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 3E3FD13A4 for ; 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Examples for this might include page poisoning in which we isolate a page and then put it back in the free list without ever having actually allocated it. This will enable us to also avoid notifiers for the future free page reporting which will need to avoid retriggering page reporting when returning pages that have been reported on. Signed-off-by: Alexander Duyck Acked-by: David Hildenbrand --- mm/internal.h | 1 + mm/page_alloc.c | 24 ++++++++++++++++++++++++ mm/page_isolation.c | 6 ++---- 3 files changed, 27 insertions(+), 4 deletions(-) diff --git a/mm/internal.h b/mm/internal.h index 3cf20ab3ca01..e1c908d0bf83 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -157,6 +157,7 @@ static inline struct page *pageblock_pfn_to_page(unsigned long start_pfn, } extern int __isolate_free_page(struct page *page, unsigned int order); +extern void __putback_isolated_page(struct page *page, unsigned int order); extern void memblock_free_pages(struct page *page, unsigned long pfn, unsigned int order); extern void __free_pages_core(struct page *page, unsigned int order); diff --git a/mm/page_alloc.c b/mm/page_alloc.c index e0a7895300fb..500b242c6f7f 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3228,6 +3228,30 @@ int __isolate_free_page(struct page *page, unsigned int order) return 1UL << order; } +/** + * __putback_isolated_page - Return a now-isolated page back where we got it + * @page: Page that was isolated + * @order: Order of the isolated page + * + * This function is meant to return a page pulled from the free lists via + * __isolate_free_page back to the free lists they were pulled from. + */ +void __putback_isolated_page(struct page *page, unsigned int order) +{ + struct zone *zone = page_zone(page); + unsigned long pfn; + unsigned int mt; + + /* zone lock should be held when this function is called */ + lockdep_assert_held(&zone->lock); + + pfn = page_to_pfn(page); + mt = get_pfnblock_migratetype(page, pfn); + + /* Return isolated page to tail of freelist. */ + __free_one_page(page, pfn, zone, order, mt); +} + /* * Update NUMA hit/miss statistics * diff --git a/mm/page_isolation.c b/mm/page_isolation.c index 04ee1663cdbe..d93d2be0070f 100644 --- a/mm/page_isolation.c +++ b/mm/page_isolation.c @@ -134,13 +134,11 @@ static void unset_migratetype_isolate(struct page *page, unsigned migratetype) __mod_zone_freepage_state(zone, nr_pages, migratetype); } set_pageblock_migratetype(page, migratetype); + if (isolated_page) + __putback_isolated_page(page, order); zone->nr_isolate_pageblock--; out: spin_unlock_irqrestore(&zone->lock, flags); - if (isolated_page) { - post_alloc_hook(page, order, __GFP_MOVABLE); - __free_pages(page, order); - } } static inline struct page * From patchwork Thu Dec 5 16:22:38 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Duyck X-Patchwork-Id: 11275165 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id D487E14BD for ; Thu, 5 Dec 2019 16:22:45 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 7939424249 for ; Thu, 5 Dec 2019 16:22:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="YJ3H5mXh" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7939424249 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 836186B1115; Thu, 5 Dec 2019 11:22:44 -0500 (EST) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id 80C796B1116; 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To accomplish this, this patch adds the concept of a Reported Buddy, which is essentially meant to just be the Uptodate flag used in conjunction with the Buddy page type. To prevent the reported pages from leaking outside of the buddy lists I added a check to clear the PageReported bit in the del_page_from_free_list function. As a result any reported page that is split, merged, or allocated will have the flag cleared prior to the PageBuddy value being cleared. The process for reporting pages is fairly simple. Once we free a page that meets the minimum order for page reporting we will schedule a worker thread to start 2s or more in the future. That worker thread will begin working from the lowest supported page reporting order up to MAX_ORDER - 1 pulling unreported pages from the free list and storing them in the scatterlist. When processing each individual free list it is necessary for the worker thread to release the zone lock when it needs to stop and report the full scatterlist of pages. To reduce the work of the next iteration the worker thread will rotate the free list so that the first unreported page in the free list becomes the first entry in the list. It will then call a reporting function providing information on how many entries are in the scatterlist. Once the function completes it will return the pages to the free area from which they were allocated and start over pulling more pages from the free areas until there are no longer enough pages to report on to keep the worker busy, or we have processed as many pages as were contained in the free area when we started processing the list. The worker thread will work in a round-robin fashion making its way though each zone requesting reporting, and through each reportable free list within that zone. Once all free areas within the zone have been processed it will check to see if there have been any requests for reporting while it was processing. If so it will reschedule the worker thread to start up again in roughly 2s and exit. Signed-off-by: Alexander Duyck --- include/linux/page-flags.h | 11 + include/linux/page_reporting.h | 25 +++ mm/Kconfig | 11 + mm/Makefile | 1 mm/page_alloc.c | 17 ++ mm/page_reporting.c | 336 ++++++++++++++++++++++++++++++++++++++++ mm/page_reporting.h | 54 ++++++ 7 files changed, 451 insertions(+), 4 deletions(-) create mode 100644 include/linux/page_reporting.h create mode 100644 mm/page_reporting.c create mode 100644 mm/page_reporting.h diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 1bf83c8fcaa7..49c2697046b9 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -163,6 +163,9 @@ enum pageflags { /* non-lru isolated movable page */ PG_isolated = PG_reclaim, + + /* Only valid for buddy pages. Used to track pages that are reported */ + PG_reported = PG_uptodate, }; #ifndef __GENERATING_BOUNDS_H @@ -432,6 +435,14 @@ static inline bool set_hwpoison_free_buddy_page(struct page *page) #endif /* + * PageReported() is used to track reported free pages within the Buddy + * allocator. We can use the non-atomic version of the test and set + * operations as both should be shielded with the zone lock to prevent + * any possible races on the setting or clearing of the bit. + */ +__PAGEFLAG(Reported, reported, PF_NO_COMPOUND) + +/* * On an anonymous page mapped into a user virtual memory area, * page->mapping points to its anon_vma, not to a struct address_space; * with the PAGE_MAPPING_ANON bit set to distinguish it. See rmap.h. diff --git a/include/linux/page_reporting.h b/include/linux/page_reporting.h new file mode 100644 index 000000000000..32355486f572 --- /dev/null +++ b/include/linux/page_reporting.h @@ -0,0 +1,25 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_PAGE_REPORTING_H +#define _LINUX_PAGE_REPORTING_H + +#include +#include + +#define PAGE_REPORTING_CAPACITY 32 + +struct page_reporting_dev_info { + /* function that alters pages to make them "reported" */ + int (*report)(struct page_reporting_dev_info *prdev, + struct scatterlist *sg, unsigned int nents); + + /* work struct for processing reports */ + struct delayed_work work; + + /* Current state of page reporting */ + atomic_t state; +}; + +/* Tear-down and bring-up for page reporting devices */ +void page_reporting_unregister(struct page_reporting_dev_info *prdev); +int page_reporting_register(struct page_reporting_dev_info *prdev); +#endif /*_LINUX_PAGE_REPORTING_H */ diff --git a/mm/Kconfig b/mm/Kconfig index ab80933be65f..d40a873402ff 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -237,6 +237,17 @@ config COMPACTION linux-mm@kvack.org. # +# support for free page reporting +config PAGE_REPORTING + bool "Free page reporting" + def_bool n + help + Free page reporting allows for the incremental acquisition of + free pages from the buddy allocator for the purpose of reporting + those pages to another entity, such as a hypervisor, so that the + memory can be freed within the host for other uses. + +# # support for page migration # config MIGRATION diff --git a/mm/Makefile b/mm/Makefile index 059115e6efb4..e55649063735 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -117,3 +117,4 @@ obj-$(CONFIG_ZONE_DEVICE) += memremap.o obj-$(CONFIG_HMM_MIRROR) += hmm.o obj-$(CONFIG_MEMFD_CREATE) += memfd.o obj-$(CONFIG_MAPPING_DIRTY_HELPERS) += mapping_dirty_helpers.o +obj-$(CONFIG_PAGE_REPORTING) += page_reporting.o diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 500b242c6f7f..290148398c26 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -74,6 +74,7 @@ #include #include "internal.h" #include "shuffle.h" +#include "page_reporting.h" /* prevent >1 _updater_ of zone percpu pageset ->high and ->batch fields */ static DEFINE_MUTEX(pcp_batch_high_lock); @@ -909,6 +910,10 @@ static inline void move_to_free_list(struct page *page, struct zone *zone, static inline void del_page_from_free_list(struct page *page, struct zone *zone, unsigned int order) { + /* clear reported state and update reported page count */ + if (page_reported(page)) + __ClearPageReported(page); + list_del(&page->lru); __ClearPageBuddy(page); set_page_private(page, 0); @@ -972,7 +977,7 @@ static inline void del_page_from_free_list(struct page *page, struct zone *zone, static inline void __free_one_page(struct page *page, unsigned long pfn, struct zone *zone, unsigned int order, - int migratetype) + int migratetype, bool report) { struct capture_control *capc = task_capc(zone); unsigned long uninitialized_var(buddy_pfn); @@ -1057,6 +1062,10 @@ static inline void __free_one_page(struct page *page, add_to_free_list_tail(page, zone, order, migratetype); else add_to_free_list(page, zone, order, migratetype); + + /* Notify page reporting subsystem of freed page */ + if (report) + page_reporting_notify_free(order); } /* @@ -1373,7 +1382,7 @@ static void free_pcppages_bulk(struct zone *zone, int count, if (unlikely(isolated_pageblocks)) mt = get_pageblock_migratetype(page); - __free_one_page(page, page_to_pfn(page), zone, 0, mt); + __free_one_page(page, page_to_pfn(page), zone, 0, mt, true); trace_mm_page_pcpu_drain(page, 0, mt); } spin_unlock(&zone->lock); @@ -1389,7 +1398,7 @@ static void free_one_page(struct zone *zone, is_migrate_isolate(migratetype))) { migratetype = get_pfnblock_migratetype(page, pfn); } - __free_one_page(page, pfn, zone, order, migratetype); + __free_one_page(page, pfn, zone, order, migratetype, true); spin_unlock(&zone->lock); } @@ -3249,7 +3258,7 @@ void __putback_isolated_page(struct page *page, unsigned int order) mt = get_pfnblock_migratetype(page, pfn); /* Return isolated page to tail of freelist. */ - __free_one_page(page, pfn, zone, order, mt); + __free_one_page(page, pfn, zone, order, mt, false); } /* diff --git a/mm/page_reporting.c b/mm/page_reporting.c new file mode 100644 index 000000000000..90154e71d6f9 --- /dev/null +++ b/mm/page_reporting.c @@ -0,0 +1,336 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include +#include +#include + +#include "page_reporting.h" +#include "internal.h" + +#define PAGE_REPORTING_DELAY (2 * HZ) +static struct page_reporting_dev_info __rcu *pr_dev_info __read_mostly; + +enum { + PAGE_REPORTING_IDLE = 0, + PAGE_REPORTING_REQUESTED, + PAGE_REPORTING_ACTIVE +}; + +/* request page reporting */ +static void +__page_reporting_request(struct page_reporting_dev_info *prdev) +{ + unsigned int state; + + /* Check to see if we are in desired state */ + state = atomic_read(&prdev->state); + if (state == PAGE_REPORTING_REQUESTED) + return; + + /* + * If reporting is already active there is nothing we need to do. + * Test against 0 as that represents PAGE_REPORTING_IDLE. + */ + state = atomic_xchg(&prdev->state, PAGE_REPORTING_REQUESTED); + if (state != PAGE_REPORTING_IDLE) + return; + + /* + * Delay the start of work to allow a sizable queue to build. For + * now we are limiting this to running no more than once every + * couple of seconds. + */ + schedule_delayed_work(&prdev->work, PAGE_REPORTING_DELAY); +} + +/* notify prdev of free page reporting request */ +void __page_reporting_notify(void) +{ + struct page_reporting_dev_info *prdev; + + /* + * We use RCU to protect the pr_dev_info pointer. In almost all + * cases this should be present, however in the unlikely case of + * a shutdown this will be NULL and we should exit. + */ + rcu_read_lock(); + prdev = rcu_dereference(pr_dev_info); + if (likely(prdev)) + __page_reporting_request(prdev); + + rcu_read_unlock(); +} + +static void +page_reporting_drain(struct page_reporting_dev_info *prdev, + struct scatterlist *sgl, unsigned int nents, bool reported) +{ + struct scatterlist *sg = sgl; + + /* + * Drain the now reported pages back into their respective + * free lists/areas. We assume at least one page is populated. + */ + do { + unsigned int order = get_order(sg->length); + struct page *page = sg_page(sg); + + __putback_isolated_page(page, order); + + /* If the pages were not reported due to error skip flagging */ + if (!reported) + continue; + + /* + * If page was not comingled with another page we can + * consider the result to be "reported" since the page + * hasn't been modified, otherwise we will need to + * report on the new larger page when we make our way + * up to that higher order. + */ + if (PageBuddy(page) && page_order(page) == order) + __SetPageReported(page); + } while ((sg = sg_next(sg))); + + /* reinitialize scatterlist now that it is empty */ + sg_init_table(sgl, nents); +} + +/* + * The page reporting cycle consists of 4 stages, fill, report, drain, and + * idle. We will cycle through the first 3 stages until we cannot obtain a + * full scatterlist of pages, in that case we will switch to idle. + */ +static int +page_reporting_cycle(struct page_reporting_dev_info *prdev, struct zone *zone, + unsigned int order, unsigned int mt, + struct scatterlist *sgl, unsigned int *offset) +{ + struct free_area *area = &zone->free_area[order]; + struct list_head *list = &area->free_list[mt]; + unsigned int page_len = PAGE_SIZE << order; + struct page *page, *next; + unsigned long budget; + int err = 0; + + /* + * Perform early check, if free area is empty there is + * nothing to process so we can skip this free_list. + */ + if (list_empty(list)) + return err; + + spin_lock_irq(&zone->lock); + + /* + * Only process as many pages are are present at the start of this + * call. If additional pages are freed we can process them in a + * couple seconds when we start the next pass. + * + * The assumption with this is that most of the pages are of one + * migratetype so we should really only need this for one of the + * lists in a given free area. + */ + budget = area->nr_free; + + /* loop through free list adding unreported pages to sg list */ + list_for_each_entry_safe(page, next, list, lru) { + /* If we consumed our budget we should go idle for now */ + if (!budget--) + break; + + /* We are going to skip over the reported pages. */ + if (PageReported(page)) + continue; + + /* Attempt to add page to sg list */ + if (*offset) { + if (!__isolate_free_page(page, order)) + break; + + sg_set_page(&sgl[--(*offset)], page, page_len, 0); + continue; + } + + /* + * Make the first non-reported entry in the free list + * the new head of the free list before we exit. + */ + if (!list_is_first(&page->lru, list)) + list_rotate_to_front(&page->lru, list); + + /* release lock before waiting on report processing */ + spin_unlock_irq(&zone->lock); + + /* reset entries since the full list will be reported */ + *offset = PAGE_REPORTING_CAPACITY; + + /* begin processing pages in local list */ + err = prdev->report(prdev, sgl, PAGE_REPORTING_CAPACITY); + + /* reacquire zone lock and resume processing */ + spin_lock_irq(&zone->lock); + + /* flush reported pages from the sg list */ + page_reporting_drain(prdev, sgl, PAGE_REPORTING_CAPACITY, !err); + + /* exit on error */ + if (err) + break; + + /* + * Reset next to first entry, the old next isn't valid + * since we dropped the lock to report the pages + */ + next = list_first_entry(list, struct page, lru); + } + + spin_unlock_irq(&zone->lock); + + return err; +} + +static int +page_reporting_process_zone(struct page_reporting_dev_info *prdev, + struct scatterlist *sgl, struct zone *zone) +{ + unsigned int order, mt, leftover, offset = PAGE_REPORTING_CAPACITY; + unsigned long watermark; + int err = 0; + + /* Generate minimum watermark to be able to guarantee progress */ + watermark = low_wmark_pages(zone) + + (PAGE_REPORTING_CAPACITY << PAGE_REPORTING_MIN_ORDER); + + /* + * Cancel request if insufficient free memory or if we failed + * to allocate page reporting statistics for the zone. + */ + if (!zone_watermark_ok(zone, 0, watermark, 0, ALLOC_CMA)) + return err; + + /* Process each free list starting from lowest order/mt */ + for (order = PAGE_REPORTING_MIN_ORDER; order < MAX_ORDER; order++) { + for (mt = 0; mt < MIGRATE_TYPES; mt++) { + /* We do not pull pages from the isolate free list */ + if (is_migrate_isolate(mt)) + continue; + + err = page_reporting_cycle(prdev, zone, order, mt, + sgl, &offset); + if (err) + return err; + } + } + + /* report the leftover pages before going idle */ + leftover = PAGE_REPORTING_CAPACITY - offset; + if (leftover) { + sgl = &sgl[offset]; + err = prdev->report(prdev, sgl, leftover); + + /* flush any remaining pages out from the last report */ + spin_lock_irq(&zone->lock); + page_reporting_drain(prdev, sgl, leftover, !err); + spin_unlock_irq(&zone->lock); + } + + return err; +} + +static void page_reporting_process(struct work_struct *work) +{ + struct delayed_work *d_work = to_delayed_work(work); + struct page_reporting_dev_info *prdev = + container_of(d_work, struct page_reporting_dev_info, work); + int err = 0, state = PAGE_REPORTING_ACTIVE; + struct scatterlist *sgl; + struct zone *zone; + + /* + * Alter the state so we can detect any future requests while not + * scheculing any additional work. + */ + atomic_set(&prdev->state, state); + + /* allocate scatterlist to store pages being reported on */ + sgl = kmalloc_array(PAGE_REPORTING_CAPACITY, sizeof(*sgl), GFP_KERNEL); + if (!sgl) + goto err_out; + + sg_init_table(sgl, PAGE_REPORTING_CAPACITY); + + for_each_zone(zone) { + err = page_reporting_process_zone(prdev, sgl, zone); + if (err) + break; + } + + kfree(sgl); +err_out: + /* + * If the state has reverted back to requested then there may be + * additional pages to be processed. We will defer for 200ms to allow + * more pages to accumulate. + */ + state = atomic_cmpxchg(&prdev->state, state, PAGE_REPORTING_IDLE); + if (state == PAGE_REPORTING_REQUESTED) + schedule_delayed_work(&prdev->work, PAGE_REPORTING_DELAY); +} + +static DEFINE_MUTEX(page_reporting_mutex); +DEFINE_STATIC_KEY_FALSE(page_reporting_enabled); + +int page_reporting_register(struct page_reporting_dev_info *prdev) +{ + int err = 0; + + mutex_lock(&page_reporting_mutex); + + /* nothing to do if already in use */ + if (rcu_access_pointer(pr_dev_info)) { + err = -EBUSY; + goto err_out; + } + + /* initialize state and work structures */ + atomic_set(&prdev->state, PAGE_REPORTING_IDLE); + INIT_DELAYED_WORK(&prdev->work, &page_reporting_process); + + /* Begin initial flush of zones */ + __page_reporting_request(prdev); + + /* Assign device to allow notifications */ + rcu_assign_pointer(pr_dev_info, prdev); + + /* enable page reporting notification */ + if (!static_key_enabled(&page_reporting_enabled)) { + static_branch_enable(&page_reporting_enabled); + pr_info("Free page reporting enabled\n"); + } +err_out: + mutex_unlock(&page_reporting_mutex); + + return err; +} +EXPORT_SYMBOL_GPL(page_reporting_register); + +void page_reporting_unregister(struct page_reporting_dev_info *prdev) +{ + mutex_lock(&page_reporting_mutex); + + if (rcu_access_pointer(pr_dev_info) == prdev) { + /* Disable page reporting notification */ + RCU_INIT_POINTER(pr_dev_info, NULL); + synchronize_rcu(); + + /* Flush any existing work, and lock it out */ + cancel_delayed_work_sync(&prdev->work); + } + + mutex_unlock(&page_reporting_mutex); +} +EXPORT_SYMBOL_GPL(page_reporting_unregister); diff --git a/mm/page_reporting.h b/mm/page_reporting.h new file mode 100644 index 000000000000..aa6d37f4dc22 --- /dev/null +++ b/mm/page_reporting.h @@ -0,0 +1,54 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _MM_PAGE_REPORTING_H +#define _MM_PAGE_REPORTING_H + +#include +#include +#include +#include +#include +#include +#include + +#define PAGE_REPORTING_MIN_ORDER pageblock_order + +#ifdef CONFIG_PAGE_REPORTING +DECLARE_STATIC_KEY_FALSE(page_reporting_enabled); +void __page_reporting_notify(void); + +static inline bool page_reported(struct page *page) +{ + return static_branch_unlikely(&page_reporting_enabled) && + PageReported(page); +} + +/** + * page_reporting_notify_free - Free page notification to start page processing + * + * This function is meant to act as a screener for __page_reporting_notify + * which will determine if a give zone has crossed over the high-water mark + * that will justify us beginning page treatment. If we have crossed that + * threshold then it will start the process of pulling some pages and + * placing them in the batch list for treatment. + */ +static inline void page_reporting_notify_free(unsigned int order) +{ + /* Called from hot path in __free_one_page() */ + if (!static_branch_unlikely(&page_reporting_enabled)) + return; + + /* Determine if we have crossed reporting threshold */ + if (order < PAGE_REPORTING_MIN_ORDER) + return; + + /* This will add a few cycles, but should be called infrequently */ + __page_reporting_notify(); +} +#else /* CONFIG_PAGE_REPORTING */ +#define page_reported(_page) false + +static inline void page_reporting_notify_free(unsigned int order) +{ +} +#endif /* CONFIG_PAGE_REPORTING */ +#endif /*_MM_PAGE_REPORTING_H */ From patchwork Thu Dec 5 16:22:47 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Duyck X-Patchwork-Id: 11275169 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 642BB13A4 for ; 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However we will need the page poisoning tracking logic as well for free page reporting. As such pull it out and make it a separate bit of config in the probe function. In addition we need to add support for the more recent init_on_free feature which expects a behavior similar to page poisoning in that we expect the page to be pre-zeroed. Reviewed-by: David Hildenbrand Signed-off-by: Alexander Duyck Acked-by: Michael S. Tsirkin --- drivers/virtio/virtio_balloon.c | 23 +++++++++++++++++------ 1 file changed, 17 insertions(+), 6 deletions(-) diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index 15b7f1d8c334..252591bc7e01 100644 --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -849,7 +849,6 @@ static int virtio_balloon_register_shrinker(struct virtio_balloon *vb) static int virtballoon_probe(struct virtio_device *vdev) { struct virtio_balloon *vb; - __u32 poison_val; int err; if (!vdev->config->get) { @@ -916,11 +915,20 @@ static int virtballoon_probe(struct virtio_device *vdev) VIRTIO_BALLOON_CMD_ID_STOP); spin_lock_init(&vb->free_page_list_lock); INIT_LIST_HEAD(&vb->free_page_list); - if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) { + } + if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) { + /* Start with poison val of 0 representing general init */ + __u32 poison_val = 0; + + /* + * Let the hypervisor know that we are expecting a + * specific value to be written back in balloon pages. + */ + if (!want_init_on_free()) memset(&poison_val, PAGE_POISON, sizeof(poison_val)); - virtio_cwrite(vb->vdev, struct virtio_balloon_config, - poison_val, &poison_val); - } + + virtio_cwrite(vb->vdev, struct virtio_balloon_config, + poison_val, &poison_val); } /* * We continue to use VIRTIO_BALLOON_F_DEFLATE_ON_OOM to decide if a @@ -1021,7 +1029,10 @@ static int virtballoon_restore(struct virtio_device *vdev) static int virtballoon_validate(struct virtio_device *vdev) { - if (!page_poisoning_enabled()) + /* Tell the host whether we care about poisoned pages. */ + if (!want_init_on_free() && + (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY) || + !page_poisoning_enabled())) __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON); __virtio_clear_bit(vdev, VIRTIO_F_IOMMU_PLATFORM); From patchwork Thu Dec 5 16:22:55 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Duyck X-Patchwork-Id: 11275173 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id DE6A314BD for ; 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Reporting differs from the regular balloon functionality in that is is much less durable than a standard memory balloon. Instead of creating a list of pages that cannot be accessed the pages are only inaccessible while they are being indicated to the virtio interface. Once the interface has acknowledged them they are placed back into their respective free lists and are once again accessible by the guest system. Unlike a standard balloon we don't inflate and deflate the pages. Instead we perform the reporting, and once the reporting is completed it is assumed that the page has been dropped from the guest and will be faulted back in the next time the page is accessed. For this reason when I had originally introduced the patch set I referred to this behavior as a "bubble" instead of a "balloon" since the duration is short lived, and when the page is touched the "bubble" is popped and the page is faulted back in. Signed-off-by: Alexander Duyck Acked-by: Michael S. Tsirkin Reviewed-by: David Hildenbrand --- drivers/virtio/Kconfig | 1 + drivers/virtio/virtio_balloon.c | 64 +++++++++++++++++++++++++++++++++++ include/uapi/linux/virtio_balloon.h | 1 + 3 files changed, 66 insertions(+) diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig index 078615cf2afc..4b2dd8259ff5 100644 --- a/drivers/virtio/Kconfig +++ b/drivers/virtio/Kconfig @@ -58,6 +58,7 @@ config VIRTIO_BALLOON tristate "Virtio balloon driver" depends on VIRTIO select MEMORY_BALLOON + select PAGE_REPORTING ---help--- This driver supports increasing and decreasing the amount of memory within a KVM guest. diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index 252591bc7e01..ecd54edba968 100644 --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -19,6 +19,7 @@ #include #include #include +#include /* * Balloon device works in 4K page units. So each page is pointed to by @@ -47,6 +48,7 @@ enum virtio_balloon_vq { VIRTIO_BALLOON_VQ_DEFLATE, VIRTIO_BALLOON_VQ_STATS, VIRTIO_BALLOON_VQ_FREE_PAGE, + VIRTIO_BALLOON_VQ_REPORTING, VIRTIO_BALLOON_VQ_MAX }; @@ -114,6 +116,10 @@ struct virtio_balloon { /* To register a shrinker to shrink memory upon memory pressure */ struct shrinker shrinker; + + /* Free page reporting device */ + struct virtqueue *reporting_vq; + struct page_reporting_dev_info pr_dev_info; }; static struct virtio_device_id id_table[] = { @@ -153,6 +159,33 @@ static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq) } +int virtballoon_free_page_report(struct page_reporting_dev_info *pr_dev_info, + struct scatterlist *sg, unsigned int nents) +{ + struct virtio_balloon *vb = + container_of(pr_dev_info, struct virtio_balloon, pr_dev_info); + struct virtqueue *vq = vb->reporting_vq; + unsigned int unused, err; + + /* We should always be able to add these buffers to an empty queue. */ + err = virtqueue_add_inbuf(vq, sg, nents, vb, GFP_NOWAIT | __GFP_NOWARN); + + /* + * In the extremely unlikely case that something has occurred and we + * are able to trigger an error we will simply display a warning + * and exit without actually processing the pages. + */ + if (WARN_ON_ONCE(err)) + return err; + + virtqueue_kick(vq); + + /* When host has read buffer, this completes via balloon_ack */ + wait_event(vb->acked, virtqueue_get_buf(vq, &unused)); + + return 0; +} + static void set_page_pfns(struct virtio_balloon *vb, __virtio32 pfns[], struct page *page) { @@ -477,6 +510,7 @@ static int init_vqs(struct virtio_balloon *vb) names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate"; names[VIRTIO_BALLOON_VQ_STATS] = NULL; names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL; + names[VIRTIO_BALLOON_VQ_REPORTING] = NULL; if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { names[VIRTIO_BALLOON_VQ_STATS] = "stats"; @@ -488,6 +522,11 @@ static int init_vqs(struct virtio_balloon *vb) callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL; } + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) { + names[VIRTIO_BALLOON_VQ_REPORTING] = "reporting_vq"; + callbacks[VIRTIO_BALLOON_VQ_REPORTING] = balloon_ack; + } + err = vb->vdev->config->find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX, vqs, callbacks, names, NULL, NULL); if (err) @@ -520,6 +559,9 @@ static int init_vqs(struct virtio_balloon *vb) if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) vb->free_page_vq = vqs[VIRTIO_BALLOON_VQ_FREE_PAGE]; + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) + vb->reporting_vq = vqs[VIRTIO_BALLOON_VQ_REPORTING]; + return 0; } @@ -939,12 +981,31 @@ static int virtballoon_probe(struct virtio_device *vdev) if (err) goto out_del_balloon_wq; } + + vb->pr_dev_info.report = virtballoon_free_page_report; + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) { + unsigned int capacity; + + capacity = virtqueue_get_vring_size(vb->reporting_vq); + if (capacity < PAGE_REPORTING_CAPACITY) { + err = -ENOSPC; + goto out_unregister_shrinker; + } + + err = page_reporting_register(&vb->pr_dev_info); + if (err) + goto out_unregister_shrinker; + } + virtio_device_ready(vdev); if (towards_target(vb)) virtballoon_changed(vdev); return 0; +out_unregister_shrinker: + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) + virtio_balloon_unregister_shrinker(vb); out_del_balloon_wq: if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) destroy_workqueue(vb->balloon_wq); @@ -973,6 +1034,8 @@ static void virtballoon_remove(struct virtio_device *vdev) { struct virtio_balloon *vb = vdev->priv; + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) + page_reporting_unregister(&vb->pr_dev_info); if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) virtio_balloon_unregister_shrinker(vb); spin_lock_irq(&vb->stop_update_lock); @@ -1045,6 +1108,7 @@ static int virtballoon_validate(struct virtio_device *vdev) VIRTIO_BALLOON_F_DEFLATE_ON_OOM, VIRTIO_BALLOON_F_FREE_PAGE_HINT, VIRTIO_BALLOON_F_PAGE_POISON, + VIRTIO_BALLOON_F_REPORTING, }; static struct virtio_driver virtio_balloon_driver = { diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h index a1966cd7b677..19974392d324 100644 --- a/include/uapi/linux/virtio_balloon.h +++ b/include/uapi/linux/virtio_balloon.h @@ -36,6 +36,7 @@ #define VIRTIO_BALLOON_F_DEFLATE_ON_OOM 2 /* Deflate balloon on OOM */ #define VIRTIO_BALLOON_F_FREE_PAGE_HINT 3 /* VQ to report free pages */ #define VIRTIO_BALLOON_F_PAGE_POISON 4 /* Guest is using page poisoning */ +#define VIRTIO_BALLOON_F_REPORTING 5 /* Page reporting virtqueue */ /* Size of a PFN in the balloon interface. */ #define VIRTIO_BALLOON_PFN_SHIFT 12 From patchwork Thu Dec 5 16:23:04 2019 Content-Type: text/plain; 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Currently the only consumer is virtio-balloon, however it is possible that other drivers might make use of this so it is best to add a bit of documetation explaining at a high level how to use the API. Signed-off-by: Alexander Duyck --- Documentation/vm/free_page_reporting.rst | 41 ++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) create mode 100644 Documentation/vm/free_page_reporting.rst diff --git a/Documentation/vm/free_page_reporting.rst b/Documentation/vm/free_page_reporting.rst new file mode 100644 index 000000000000..33f54a450a4a --- /dev/null +++ b/Documentation/vm/free_page_reporting.rst @@ -0,0 +1,41 @@ +.. _free_page_reporting: + +===================== +Free Page Reporting +===================== + +Free page reporting is an API by which a device can register to receive +lists of pages that are currently unused by the system. This is useful in +the case of virtualization where a guest is then able to use this data to +notify the hypervisor that it is no longer using certain pages in memory. + +For the driver, typically a balloon driver, to use of this functionality +it will allocate and initialize a page_reporting_dev_info structure. The +field within the structure it will populate is the "report" function +pointer used to process the scatterlist. It must also guarantee that it can +handle at least PAGE_REPORTING_CAPACITY worth of scatterlist entries per +call to the function. A call to page_reporting_register will register the +page reporting interface with the reporting framework assuming no other +page reporting devices are already registered. + +Once registered the page reporting API will begin reporting batches of +pages to the driver. The API will start reporting pages 2 seconds after +the interface is registered and will continue to do so 2 seconds after any +page of a sufficiently high order is freed. + +Pages reported will be stored in the scatterlist passed to the reporting +function with the final entry having the end bit set in entry nent - 1. +While pages are being processed by the report function they will not be +accessible to the allocator. Once the report function has been completed +the pages will be returned to the free area from which they were obtained. + +Prior to removing a driver that is making use of free page reporting it +is necessary to call page_reporting_unregister to have the +page_reporting_dev_info structure that is currently in use by free page +reporting removed. Doing this will prevent further reports from being +issued via the interface. If another driver or the same driver is +registered it is possible for it to resume where the previous driver had +left off in terms of reporting free pages. + +Alexander Duyck, Dec 04, 2019 +