1 files changed, 729 insertions, 0 deletions

diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
new file mode 100644
index 000000000..cf8a9fc5c
--- /dev/null
+++ b/mm/damon/vaddr.c
@@ -0,0 +1,729 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * DAMON Primitives for Virtual Address Spaces
+ *
+ * Author: SeongJae Park <sjpark@amazon.de>
+ */
+
+#define pr_fmt(fmt) "damon-va: " fmt
+
+#include <asm-generic/mman-common.h>
+#include <linux/highmem.h>
+#include <linux/hugetlb.h>
+#include <linux/mmu_notifier.h>
+#include <linux/page_idle.h>
+#include <linux/pagewalk.h>
+#include <linux/sched/mm.h>
+
+#include "ops-common.h"
+
+#ifdef CONFIG_DAMON_VADDR_KUNIT_TEST
+#undef DAMON_MIN_REGION
+#define DAMON_MIN_REGION 1
+#endif
+
+/*
+ * 't->pid' should be the pointer to the relevant 'struct pid' having reference
+ * count.  Caller must put the returned task, unless it is NULL.
+ */
+static inline struct task_struct *damon_get_task_struct(struct damon_target *t)
+{
+	return get_pid_task(t->pid, PIDTYPE_PID);
+}
+
+/*
+ * Get the mm_struct of the given target
+ *
+ * Caller _must_ put the mm_struct after use, unless it is NULL.
+ *
+ * Returns the mm_struct of the target on success, NULL on failure
+ */
+static struct mm_struct *damon_get_mm(struct damon_target *t)
+{
+	struct task_struct *task;
+	struct mm_struct *mm;
+
+	task = damon_get_task_struct(t);
+	if (!task)
+		return NULL;
+
+	mm = get_task_mm(task);
+	put_task_struct(task);
+	return mm;
+}
+
+/*
+ * Functions for the initial monitoring target regions construction
+ */
+
+/*
+ * Size-evenly split a region into 'nr_pieces' small regions
+ *
+ * Returns 0 on success, or negative error code otherwise.
+ */
+static int damon_va_evenly_split_region(struct damon_target *t,
+		struct damon_region *r, unsigned int nr_pieces)
+{
+	unsigned long sz_orig, sz_piece, orig_end;
+	struct damon_region *n = NULL, *next;
+	unsigned long start;
+
+	if (!r || !nr_pieces)
+		return -EINVAL;
+
+	orig_end = r->ar.end;
+	sz_orig = damon_sz_region(r);
+	sz_piece = ALIGN_DOWN(sz_orig / nr_pieces, DAMON_MIN_REGION);
+
+	if (!sz_piece)
+		return -EINVAL;
+
+	r->ar.end = r->ar.start + sz_piece;
+	next = damon_next_region(r);
+	for (start = r->ar.end; start + sz_piece <= orig_end;
+			start += sz_piece) {
+		n = damon_new_region(start, start + sz_piece);
+		if (!n)
+			return -ENOMEM;
+		damon_insert_region(n, r, next, t);
+		r = n;
+	}
+	/* complement last region for possible rounding error */
+	if (n)
+		n->ar.end = orig_end;
+
+	return 0;
+}
+
+static unsigned long sz_range(struct damon_addr_range *r)
+{
+	return r->end - r->start;
+}
+
+/*
+ * Find three regions separated by two biggest unmapped regions
+ *
+ * vma		the head vma of the target address space
+ * regions	an array of three address ranges that results will be saved
+ *
+ * This function receives an address space and finds three regions in it which
+ * separated by the two biggest unmapped regions in the space.  Please refer to
+ * below comments of '__damon_va_init_regions()' function to know why this is
+ * necessary.
+ *
+ * Returns 0 if success, or negative error code otherwise.
+ */
+static int __damon_va_three_regions(struct mm_struct *mm,
+				       struct damon_addr_range regions[3])
+{
+	struct damon_addr_range first_gap = {0}, second_gap = {0};
+	VMA_ITERATOR(vmi, mm, 0);
+	struct vm_area_struct *vma, *prev = NULL;
+	unsigned long start;
+
+	/*
+	 * Find the two biggest gaps so that first_gap > second_gap > others.
+	 * If this is too slow, it can be optimised to examine the maple
+	 * tree gaps.
+	 */
+	for_each_vma(vmi, vma) {
+		unsigned long gap;
+
+		if (!prev) {
+			start = vma->vm_start;
+			goto next;
+		}
+		gap = vma->vm_start - prev->vm_end;
+
+		if (gap > sz_range(&first_gap)) {
+			second_gap = first_gap;
+			first_gap.start = prev->vm_end;
+			first_gap.end = vma->vm_start;
+		} else if (gap > sz_range(&second_gap)) {
+			second_gap.start = prev->vm_end;
+			second_gap.end = vma->vm_start;
+		}
+next:
+		prev = vma;
+	}
+
+	if (!sz_range(&second_gap) || !sz_range(&first_gap))
+		return -EINVAL;
+
+	/* Sort the two biggest gaps by address */
+	if (first_gap.start > second_gap.start)
+		swap(first_gap, second_gap);
+
+	/* Store the result */
+	regions[0].start = ALIGN(start, DAMON_MIN_REGION);
+	regions[0].end = ALIGN(first_gap.start, DAMON_MIN_REGION);
+	regions[1].start = ALIGN(first_gap.end, DAMON_MIN_REGION);
+	regions[1].end = ALIGN(second_gap.start, DAMON_MIN_REGION);
+	regions[2].start = ALIGN(second_gap.end, DAMON_MIN_REGION);
+	regions[2].end = ALIGN(prev->vm_end, DAMON_MIN_REGION);
+
+	return 0;
+}
+
+/*
+ * Get the three regions in the given target (task)
+ *
+ * Returns 0 on success, negative error code otherwise.
+ */
+static int damon_va_three_regions(struct damon_target *t,
+				struct damon_addr_range regions[3])
+{
+	struct mm_struct *mm;
+	int rc;
+
+	mm = damon_get_mm(t);
+	if (!mm)
+		return -EINVAL;
+
+	mmap_read_lock(mm);
+	rc = __damon_va_three_regions(mm, regions);
+	mmap_read_unlock(mm);
+
+	mmput(mm);
+	return rc;
+}
+
+/*
+ * Initialize the monitoring target regions for the given target (task)
+ *
+ * t	the given target
+ *
+ * Because only a number of small portions of the entire address space
+ * is actually mapped to the memory and accessed, monitoring the unmapped
+ * regions is wasteful.  That said, because we can deal with small noises,
+ * tracking every mapping is not strictly required but could even incur a high
+ * overhead if the mapping frequently changes or the number of mappings is
+ * high.  The adaptive regions adjustment mechanism will further help to deal
+ * with the noise by simply identifying the unmapped areas as a region that
+ * has no access.  Moreover, applying the real mappings that would have many
+ * unmapped areas inside will make the adaptive mechanism quite complex.  That
+ * said, too huge unmapped areas inside the monitoring target should be removed
+ * to not take the time for the adaptive mechanism.
+ *
+ * For the reason, we convert the complex mappings to three distinct regions
+ * that cover every mapped area of the address space.  Also the two gaps
+ * between the three regions are the two biggest unmapped areas in the given
+ * address space.  In detail, this function first identifies the start and the
+ * end of the mappings and the two biggest unmapped areas of the address space.
+ * Then, it constructs the three regions as below:
+ *
+ *     [mappings[0]->start, big_two_unmapped_areas[0]->start)
+ *     [big_two_unmapped_areas[0]->end, big_two_unmapped_areas[1]->start)
+ *     [big_two_unmapped_areas[1]->end, mappings[nr_mappings - 1]->end)
+ *
+ * As usual memory map of processes is as below, the gap between the heap and
+ * the uppermost mmap()-ed region, and the gap between the lowermost mmap()-ed
+ * region and the stack will be two biggest unmapped regions.  Because these
+ * gaps are exceptionally huge areas in usual address space, excluding these
+ * two biggest unmapped regions will be sufficient to make a trade-off.
+ *
+ *   <heap>
+ *   <BIG UNMAPPED REGION 1>
+ *   <uppermost mmap()-ed region>
+ *   (other mmap()-ed regions and small unmapped regions)
+ *   <lowermost mmap()-ed region>
+ *   <BIG UNMAPPED REGION 2>
+ *   <stack>
+ */
+static void __damon_va_init_regions(struct damon_ctx *ctx,
+				     struct damon_target *t)
+{
+	struct damon_target *ti;
+	struct damon_region *r;
+	struct damon_addr_range regions[3];
+	unsigned long sz = 0, nr_pieces;
+	int i, tidx = 0;
+
+	if (damon_va_three_regions(t, regions)) {
+		damon_for_each_target(ti, ctx) {
+			if (ti == t)
+				break;
+			tidx++;
+		}
+		pr_debug("Failed to get three regions of %dth target\n", tidx);
+		return;
+	}
+
+	for (i = 0; i < 3; i++)
+		sz += regions[i].end - regions[i].start;
+	if (ctx->attrs.min_nr_regions)
+		sz /= ctx->attrs.min_nr_regions;
+	if (sz < DAMON_MIN_REGION)
+		sz = DAMON_MIN_REGION;
+
+	/* Set the initial three regions of the target */
+	for (i = 0; i < 3; i++) {
+		r = damon_new_region(regions[i].start, regions[i].end);
+		if (!r) {
+			pr_err("%d'th init region creation failed\n", i);
+			return;
+		}
+		damon_add_region(r, t);
+
+		nr_pieces = (regions[i].end - regions[i].start) / sz;
+		damon_va_evenly_split_region(t, r, nr_pieces);
+	}
+}
+
+/* Initialize '->regions_list' of every target (task) */
+static void damon_va_init(struct damon_ctx *ctx)
+{
+	struct damon_target *t;
+
+	damon_for_each_target(t, ctx) {
+		/* the user may set the target regions as they want */
+		if (!damon_nr_regions(t))
+			__damon_va_init_regions(ctx, t);
+	}
+}
+
+/*
+ * Update regions for current memory mappings
+ */
+static void damon_va_update(struct damon_ctx *ctx)
+{
+	struct damon_addr_range three_regions[3];
+	struct damon_target *t;
+
+	damon_for_each_target(t, ctx) {
+		if (damon_va_three_regions(t, three_regions))
+			continue;
+		damon_set_regions(t, three_regions, 3);
+	}
+}
+
+static int damon_mkold_pmd_entry(pmd_t *pmd, unsigned long addr,
+		unsigned long next, struct mm_walk *walk)
+{
+	pte_t *pte;
+	pmd_t pmde;
+	spinlock_t *ptl;
+
+	if (pmd_trans_huge(pmdp_get(pmd))) {
+		ptl = pmd_lock(walk->mm, pmd);
+		pmde = pmdp_get(pmd);
+
+		if (!pmd_present(pmde)) {
+			spin_unlock(ptl);
+			return 0;
+		}
+
+		if (pmd_trans_huge(pmde)) {
+			damon_pmdp_mkold(pmd, walk->vma, addr);
+			spin_unlock(ptl);
+			return 0;
+		}
+		spin_unlock(ptl);
+	}
+
+	pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
+	if (!pte) {
+		walk->action = ACTION_AGAIN;
+		return 0;
+	}
+	if (!pte_present(ptep_get(pte)))
+		goto out;
+	damon_ptep_mkold(pte, walk->vma, addr);
+out:
+	pte_unmap_unlock(pte, ptl);
+	return 0;
+}
+
+#ifdef CONFIG_HUGETLB_PAGE
+static void damon_hugetlb_mkold(pte_t *pte, struct mm_struct *mm,
+				struct vm_area_struct *vma, unsigned long addr)
+{
+	bool referenced = false;
+	pte_t entry = huge_ptep_get(pte);
+	struct folio *folio = pfn_folio(pte_pfn(entry));
+	unsigned long psize = huge_page_size(hstate_vma(vma));
+
+	folio_get(folio);
+
+	if (pte_young(entry)) {
+		referenced = true;
+		entry = pte_mkold(entry);
+		set_huge_pte_at(mm, addr, pte, entry, psize);
+	}
+
+#ifdef CONFIG_MMU_NOTIFIER
+	if (mmu_notifier_clear_young(mm, addr,
+				     addr + huge_page_size(hstate_vma(vma))))
+		referenced = true;
+#endif /* CONFIG_MMU_NOTIFIER */
+
+	if (referenced)
+		folio_set_young(folio);
+
+	folio_set_idle(folio);
+	folio_put(folio);
+}
+
+static int damon_mkold_hugetlb_entry(pte_t *pte, unsigned long hmask,
+				     unsigned long addr, unsigned long end,
+				     struct mm_walk *walk)
+{
+	struct hstate *h = hstate_vma(walk->vma);
+	spinlock_t *ptl;
+	pte_t entry;
+
+	ptl = huge_pte_lock(h, walk->mm, pte);
+	entry = huge_ptep_get(pte);
+	if (!pte_present(entry))
+		goto out;
+
+	damon_hugetlb_mkold(pte, walk->mm, walk->vma, addr);
+
+out:
+	spin_unlock(ptl);
+	return 0;
+}
+#else
+#define damon_mkold_hugetlb_entry NULL
+#endif /* CONFIG_HUGETLB_PAGE */
+
+static const struct mm_walk_ops damon_mkold_ops = {
+	.pmd_entry = damon_mkold_pmd_entry,
+	.hugetlb_entry = damon_mkold_hugetlb_entry,
+	.walk_lock = PGWALK_RDLOCK,
+};
+
+static void damon_va_mkold(struct mm_struct *mm, unsigned long addr)
+{
+	mmap_read_lock(mm);
+	walk_page_range(mm, addr, addr + 1, &damon_mkold_ops, NULL);
+	mmap_read_unlock(mm);
+}
+
+/*
+ * Functions for the access checking of the regions
+ */
+
+static void __damon_va_prepare_access_check(struct mm_struct *mm,
+					struct damon_region *r)
+{
+	r->sampling_addr = damon_rand(r->ar.start, r->ar.end);
+
+	damon_va_mkold(mm, r->sampling_addr);
+}
+
+static void damon_va_prepare_access_checks(struct damon_ctx *ctx)
+{
+	struct damon_target *t;
+	struct mm_struct *mm;
+	struct damon_region *r;
+
+	damon_for_each_target(t, ctx) {
+		mm = damon_get_mm(t);
+		if (!mm)
+			continue;
+		damon_for_each_region(r, t)
+			__damon_va_prepare_access_check(mm, r);
+		mmput(mm);
+	}
+}
+
+struct damon_young_walk_private {
+	/* size of the folio for the access checked virtual memory address */
+	unsigned long *folio_sz;
+	bool young;
+};
+
+static int damon_young_pmd_entry(pmd_t *pmd, unsigned long addr,
+		unsigned long next, struct mm_walk *walk)
+{
+	pte_t *pte;
+	pte_t ptent;
+	spinlock_t *ptl;
+	struct folio *folio;
+	struct damon_young_walk_private *priv = walk->private;
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+	if (pmd_trans_huge(pmdp_get(pmd))) {
+		pmd_t pmde;
+
+		ptl = pmd_lock(walk->mm, pmd);
+		pmde = pmdp_get(pmd);
+
+		if (!pmd_present(pmde)) {
+			spin_unlock(ptl);
+			return 0;
+		}
+
+		if (!pmd_trans_huge(pmde)) {
+			spin_unlock(ptl);
+			goto regular_page;
+		}
+		folio = damon_get_folio(pmd_pfn(pmde));
+		if (!folio)
+			goto huge_out;
+		if (pmd_young(pmde) || !folio_test_idle(folio) ||
+					mmu_notifier_test_young(walk->mm,
+						addr))
+			priv->young = true;
+		*priv->folio_sz = HPAGE_PMD_SIZE;
+		folio_put(folio);
+huge_out:
+		spin_unlock(ptl);
+		return 0;
+	}
+
+regular_page:
+#endif	/* CONFIG_TRANSPARENT_HUGEPAGE */
+
+	pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
+	if (!pte) {
+		walk->action = ACTION_AGAIN;
+		return 0;
+	}
+	ptent = ptep_get(pte);
+	if (!pte_present(ptent))
+		goto out;
+	folio = damon_get_folio(pte_pfn(ptent));
+	if (!folio)
+		goto out;
+	if (pte_young(ptent) || !folio_test_idle(folio) ||
+			mmu_notifier_test_young(walk->mm, addr))
+		priv->young = true;
+	*priv->folio_sz = folio_size(folio);
+	folio_put(folio);
+out:
+	pte_unmap_unlock(pte, ptl);
+	return 0;
+}
+
+#ifdef CONFIG_HUGETLB_PAGE
+static int damon_young_hugetlb_entry(pte_t *pte, unsigned long hmask,
+				     unsigned long addr, unsigned long end,
+				     struct mm_walk *walk)
+{
+	struct damon_young_walk_private *priv = walk->private;
+	struct hstate *h = hstate_vma(walk->vma);
+	struct folio *folio;
+	spinlock_t *ptl;
+	pte_t entry;
+
+	ptl = huge_pte_lock(h, walk->mm, pte);
+	entry = huge_ptep_get(pte);
+	if (!pte_present(entry))
+		goto out;
+
+	folio = pfn_folio(pte_pfn(entry));
+	folio_get(folio);
+
+	if (pte_young(entry) || !folio_test_idle(folio) ||
+	    mmu_notifier_test_young(walk->mm, addr))
+		priv->young = true;
+	*priv->folio_sz = huge_page_size(h);
+
+	folio_put(folio);
+
+out:
+	spin_unlock(ptl);
+	return 0;
+}
+#else
+#define damon_young_hugetlb_entry NULL
+#endif /* CONFIG_HUGETLB_PAGE */
+
+static const struct mm_walk_ops damon_young_ops = {
+	.pmd_entry = damon_young_pmd_entry,
+	.hugetlb_entry = damon_young_hugetlb_entry,
+	.walk_lock = PGWALK_RDLOCK,
+};
+
+static bool damon_va_young(struct mm_struct *mm, unsigned long addr,
+		unsigned long *folio_sz)
+{
+	struct damon_young_walk_private arg = {
+		.folio_sz = folio_sz,
+		.young = false,
+	};
+
+	mmap_read_lock(mm);
+	walk_page_range(mm, addr, addr + 1, &damon_young_ops, &arg);
+	mmap_read_unlock(mm);
+	return arg.young;
+}
+
+/*
+ * Check whether the region was accessed after the last preparation
+ *
+ * mm	'mm_struct' for the given virtual address space
+ * r	the region to be checked
+ */
+static void __damon_va_check_access(struct mm_struct *mm,
+				struct damon_region *r, bool same_target)
+{
+	static unsigned long last_addr;
+	static unsigned long last_folio_sz = PAGE_SIZE;
+	static bool last_accessed;
+
+	/* If the region is in the last checked page, reuse the result */
+	if (same_target && (ALIGN_DOWN(last_addr, last_folio_sz) ==
+				ALIGN_DOWN(r->sampling_addr, last_folio_sz))) {
+		if (last_accessed)
+			r->nr_accesses++;
+		return;
+	}
+
+	last_accessed = damon_va_young(mm, r->sampling_addr, &last_folio_sz);
+	if (last_accessed)
+		r->nr_accesses++;
+
+	last_addr = r->sampling_addr;
+}
+
+static unsigned int damon_va_check_accesses(struct damon_ctx *ctx)
+{
+	struct damon_target *t;
+	struct mm_struct *mm;
+	struct damon_region *r;
+	unsigned int max_nr_accesses = 0;
+	bool same_target;
+
+	damon_for_each_target(t, ctx) {
+		mm = damon_get_mm(t);
+		if (!mm)
+			continue;
+		same_target = false;
+		damon_for_each_region(r, t) {
+			__damon_va_check_access(mm, r, same_target);
+			max_nr_accesses = max(r->nr_accesses, max_nr_accesses);
+			same_target = true;
+		}
+		mmput(mm);
+	}
+
+	return max_nr_accesses;
+}
+
+/*
+ * Functions for the target validity check and cleanup
+ */
+
+static bool damon_va_target_valid(struct damon_target *t)
+{
+	struct task_struct *task;
+
+	task = damon_get_task_struct(t);
+	if (task) {
+		put_task_struct(task);
+		return true;
+	}
+
+	return false;
+}
+
+#ifndef CONFIG_ADVISE_SYSCALLS
+static unsigned long damos_madvise(struct damon_target *target,
+		struct damon_region *r, int behavior)
+{
+	return 0;
+}
+#else
+static unsigned long damos_madvise(struct damon_target *target,
+		struct damon_region *r, int behavior)
+{
+	struct mm_struct *mm;
+	unsigned long start = PAGE_ALIGN(r->ar.start);
+	unsigned long len = PAGE_ALIGN(damon_sz_region(r));
+	unsigned long applied;
+
+	mm = damon_get_mm(target);
+	if (!mm)
+		return 0;
+
+	applied = do_madvise(mm, start, len, behavior) ? 0 : len;
+	mmput(mm);
+
+	return applied;
+}
+#endif	/* CONFIG_ADVISE_SYSCALLS */
+
+static unsigned long damon_va_apply_scheme(struct damon_ctx *ctx,
+		struct damon_target *t, struct damon_region *r,
+		struct damos *scheme)
+{
+	int madv_action;
+
+	switch (scheme->action) {
+	case DAMOS_WILLNEED:
+		madv_action = MADV_WILLNEED;
+		break;
+	case DAMOS_COLD:
+		madv_action = MADV_COLD;
+		break;
+	case DAMOS_PAGEOUT:
+		madv_action = MADV_PAGEOUT;
+		break;
+	case DAMOS_HUGEPAGE:
+		madv_action = MADV_HUGEPAGE;
+		break;
+	case DAMOS_NOHUGEPAGE:
+		madv_action = MADV_NOHUGEPAGE;
+		break;
+	case DAMOS_STAT:
+		return 0;
+	default:
+		/*
+		 * DAMOS actions that are not yet supported by 'vaddr'.
+		 */
+		return 0;
+	}
+
+	return damos_madvise(t, r, madv_action);
+}
+
+static int damon_va_scheme_score(struct damon_ctx *context,
+		struct damon_target *t, struct damon_region *r,
+		struct damos *scheme)
+{
+
+	switch (scheme->action) {
+	case DAMOS_PAGEOUT:
+		return damon_cold_score(context, r, scheme);
+	default:
+		break;
+	}
+
+	return DAMOS_MAX_SCORE;
+}
+
+static int __init damon_va_initcall(void)
+{
+	struct damon_operations ops = {
+		.id = DAMON_OPS_VADDR,
+		.init = damon_va_init,
+		.update = damon_va_update,
+		.prepare_access_checks = damon_va_prepare_access_checks,
+		.check_accesses = damon_va_check_accesses,
+		.reset_aggregated = NULL,
+		.target_valid = damon_va_target_valid,
+		.cleanup = NULL,
+		.apply_scheme = damon_va_apply_scheme,
+		.get_scheme_score = damon_va_scheme_score,
+	};
+	/* ops for fixed virtual address ranges */
+	struct damon_operations ops_fvaddr = ops;
+	int err;
+
+	/* Don't set the monitoring target regions for the entire mapping */
+	ops_fvaddr.id = DAMON_OPS_FVADDR;
+	ops_fvaddr.init = NULL;
+	ops_fvaddr.update = NULL;
+
+	err = damon_register_ops(&ops);
+	if (err)
+		return err;
+	return damon_register_ops(&ops_fvaddr);
+};
+
+subsys_initcall(damon_va_initcall);
+
+#include "vaddr-test.h"