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|
// 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));
folio_get(folio);
if (pte_young(entry)) {
referenced = true;
entry = pte_mkold(entry);
set_huge_pte_at(mm, addr, pte, entry);
}
#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"
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