[PATCH] mm: khugepaged: simplify scanning progress in pmd
From: Vernon Yang
Date: Thu Feb 26 2026 - 03:14:33 EST
From: Vernon Yang <yanglincheng@xxxxxxxxxx>
Placing "cur_progress" inside "struct collapse_control" makes the
overall code simpler, there also coincidentally has a 4-bytes hole,
as shown below:
struct collapse_control {
bool is_khugepaged; /* 0 1 */
/* XXX 3 bytes hole, try to pack */
u32 node_load[64]; /* 4 256 */
/* XXX 4 bytes hole, try to pack */
/* --- cacheline 4 boundary (256 bytes) was 8 bytes ago --- */
nodemask_t alloc_nmask; /* 264 8 */
/* size: 272, cachelines: 5, members: 3 */
/* sum members: 265, holes: 2, sum holes: 7 */
/* last cacheline: 16 bytes */
};
Also rename "cur_progress" to "progress_in_pmd", make it clearer.
No function changes.
Signed-off-by: Vernon Yang <yanglincheng@xxxxxxxxxx>
---
mm/khugepaged.c | 51 ++++++++++++++++++++++++-------------------------
1 file changed, 25 insertions(+), 26 deletions(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 7c1642fbe394..00e025f16c02 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -70,8 +70,8 @@ static struct task_struct *khugepaged_thread __read_mostly;
static DEFINE_MUTEX(khugepaged_mutex);
/*
- * default scan 8*HPAGE_PMD_NR ptes, pmd_mapped, no_pte_table or vmas
- * every 10 second.
+ * default scan 8*HPAGE_PMD_NR ptes, pte_mapped_hugepage, pmd_mapped,
+ * no_pte_table or vmas every 10 second.
*/
static unsigned int khugepaged_pages_to_scan __read_mostly;
static unsigned int khugepaged_pages_collapsed;
@@ -104,6 +104,12 @@ struct collapse_control {
/* Num pages scanned per node */
u32 node_load[MAX_NUMNODES];
+ /*
+ * Num pages scanned per pmd, include ptes,
+ * pte_mapped_hugepage, pmd_mapped or no_pte_table.
+ */
+ unsigned int progress_in_pmd;
+
/* nodemask for allocation fallback */
nodemask_t alloc_nmask;
};
@@ -1246,8 +1252,7 @@ static enum scan_result collapse_huge_page(struct mm_struct *mm, unsigned long a
static enum scan_result hpage_collapse_scan_pmd(struct mm_struct *mm,
struct vm_area_struct *vma, unsigned long start_addr,
- bool *mmap_locked, unsigned int *cur_progress,
- struct collapse_control *cc)
+ bool *mmap_locked, struct collapse_control *cc)
{
pmd_t *pmd;
pte_t *pte, *_pte;
@@ -1263,25 +1268,23 @@ static enum scan_result hpage_collapse_scan_pmd(struct mm_struct *mm,
result = find_pmd_or_thp_or_none(mm, start_addr, &pmd);
if (result != SCAN_SUCCEED) {
- if (cur_progress)
- *cur_progress = 1;
+ cc->progress_in_pmd = 1;
goto out;
}
memset(cc->node_load, 0, sizeof(cc->node_load));
nodes_clear(cc->alloc_nmask);
+ cc->progress_in_pmd = 0;
pte = pte_offset_map_lock(mm, pmd, start_addr, &ptl);
if (!pte) {
- if (cur_progress)
- *cur_progress = 1;
+ cc->progress_in_pmd = 1;
result = SCAN_NO_PTE_TABLE;
goto out;
}
for (addr = start_addr, _pte = pte; _pte < pte + HPAGE_PMD_NR;
_pte++, addr += PAGE_SIZE) {
- if (cur_progress)
- *cur_progress += 1;
+ cc->progress_in_pmd++;
pte_t pteval = ptep_get(_pte);
if (pte_none_or_zero(pteval)) {
@@ -2314,7 +2317,7 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr,
static enum scan_result hpage_collapse_scan_file(struct mm_struct *mm,
unsigned long addr, struct file *file, pgoff_t start,
- unsigned int *cur_progress, struct collapse_control *cc)
+ struct collapse_control *cc)
{
struct folio *folio = NULL;
struct address_space *mapping = file->f_mapping;
@@ -2327,6 +2330,7 @@ static enum scan_result hpage_collapse_scan_file(struct mm_struct *mm,
swap = 0;
memset(cc->node_load, 0, sizeof(cc->node_load));
nodes_clear(cc->alloc_nmask);
+ cc->progress_in_pmd = 0;
rcu_read_lock();
xas_for_each(&xas, folio, start + HPAGE_PMD_NR - 1) {
if (xas_retry(&xas, folio))
@@ -2404,12 +2408,10 @@ static enum scan_result hpage_collapse_scan_file(struct mm_struct *mm,
}
}
rcu_read_unlock();
- if (cur_progress) {
- if (result == SCAN_PTE_MAPPED_HUGEPAGE)
- *cur_progress = 1;
- else
- *cur_progress = HPAGE_PMD_NR;
- }
+ if (result == SCAN_PTE_MAPPED_HUGEPAGE)
+ cc->progress_in_pmd = 1;
+ else
+ cc->progress_in_pmd = HPAGE_PMD_NR;
if (result == SCAN_SUCCEED) {
if (cc->is_khugepaged &&
@@ -2434,7 +2436,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, enum scan_result
struct mm_slot *slot;
struct mm_struct *mm;
struct vm_area_struct *vma;
- int progress = 0;
+ unsigned int progress = 0;
VM_BUG_ON(!pages);
lockdep_assert_held(&khugepaged_mm_lock);
@@ -2488,7 +2490,6 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, enum scan_result
while (khugepaged_scan.address < hend) {
bool mmap_locked = true;
- unsigned int cur_progress = 0;
cond_resched();
if (unlikely(hpage_collapse_test_exit_or_disable(mm)))
@@ -2505,8 +2506,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, enum scan_result
mmap_read_unlock(mm);
mmap_locked = false;
*result = hpage_collapse_scan_file(mm,
- khugepaged_scan.address, file, pgoff,
- &cur_progress, cc);
+ khugepaged_scan.address, file, pgoff, cc);
fput(file);
if (*result == SCAN_PTE_MAPPED_HUGEPAGE) {
mmap_read_lock(mm);
@@ -2520,8 +2520,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, enum scan_result
}
} else {
*result = hpage_collapse_scan_pmd(mm, vma,
- khugepaged_scan.address, &mmap_locked,
- &cur_progress, cc);
+ khugepaged_scan.address, &mmap_locked, cc);
}
if (*result == SCAN_SUCCEED)
@@ -2529,7 +2528,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, enum scan_result
/* move to next address */
khugepaged_scan.address += HPAGE_PMD_SIZE;
- progress += cur_progress;
+ progress += cc->progress_in_pmd;
if (!mmap_locked)
/*
* We released mmap_lock so break loop. Note
@@ -2852,7 +2851,7 @@ int madvise_collapse(struct vm_area_struct *vma, unsigned long start,
mmap_locked = false;
*lock_dropped = true;
result = hpage_collapse_scan_file(mm, addr, file, pgoff,
- NULL, cc);
+ cc);
if (result == SCAN_PAGE_DIRTY_OR_WRITEBACK && !triggered_wb &&
mapping_can_writeback(file->f_mapping)) {
@@ -2867,7 +2866,7 @@ int madvise_collapse(struct vm_area_struct *vma, unsigned long start,
fput(file);
} else {
result = hpage_collapse_scan_pmd(mm, vma, addr,
- &mmap_locked, NULL, cc);
+ &mmap_locked, cc);
}
if (!mmap_locked)
*lock_dropped = true;
--
2.51.0