[v15,4/7] mm: Introduce Reported pages

Message ID	20191205162238.19548.68238.stgit@localhost.localdomain (mailing list archive)
State	New, archived
Headers	show Return-Path: <SRS0=8yH2=Z3=kvack.org=owner-linux-mm@kernel.org> DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7939424249 Subject: [PATCH v15 4/7] mm: Introduce Reported pages From: Alexander Duyck <alexander.duyck@gmail.com> To: kvm@vger.kernel.org, mst@redhat.com, linux-kernel@vger.kernel.org, willy@infradead.org, mhocko@kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, mgorman@techsingularity.net, vbabka@suse.cz Cc: yang.zhang.wz@gmail.com, nitesh@redhat.com, konrad.wilk@oracle.com, david@redhat.com, pagupta@redhat.com, riel@surriel.com, lcapitulino@redhat.com, dave.hansen@intel.com, wei.w.wang@intel.com, aarcange@redhat.com, pbonzini@redhat.com, dan.j.williams@intel.com, alexander.h.duyck@linux.intel.com, osalvador@suse.de Date: Thu, 05 Dec 2019 08:22:38 -0800 Message-ID: <20191205162238.19548.68238.stgit@localhost.localdomain> In-Reply-To: <20191205161928.19548.41654.stgit@localhost.localdomain> References: <20191205161928.19548.41654.stgit@localhost.localdomain> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Precedence: bulk
Series	mm / virtio: Provide support for free page reporting \| expand [v15,0/7] mm / virtio: Provide support for free page reporting [v15,1/7] mm: Adjust shuffle code to allow for future coalescing [v15,2/7] mm: Use zone and order instead of free area in free_list manipulators [v15,3/7] mm: Add function __putback_isolated_page [v15,4/7] mm: Introduce Reported pages [v15,5/7] virtio-balloon: Pull page poisoning config out of free page hinting [v15,6/7] virtio-balloon: Add support for providing free page reports to host [v15,7/7] mm: Add free page reporting documentation

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 <linux/mmzone.h> +#include <linux/scatterlist.h> + +#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 <asm/div64.h> #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 <linux/mm.h> +#include <linux/mmzone.h> +#include <linux/page_reporting.h> +#include <linux/gfp.h> +#include <linux/export.h> +#include <linux/delay.h> +#include <linux/scatterlist.h> + +#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 <linux/mmzone.h> +#include <linux/pageblock-flags.h> +#include <linux/page-isolation.h> +#include <linux/jump_label.h> +#include <linux/slab.h> +#include <asm/pgtable.h> +#include <linux/scatterlist.h> + +#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 */

[v15,4/7] mm: Introduce Reported pages

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