* [PATCH] mm: khugepaged: simplify scanning progress in pmd
@ 2026-02-26 8:13 Vernon Yang
2026-02-26 8:42 ` David Hildenbrand (Arm)
0 siblings, 1 reply; 4+ messages in thread
From: Vernon Yang @ 2026-02-26 8:13 UTC (permalink / raw)
To: akpm, david
Cc: lorenzo.stoakes, ziy, dev.jain, baohua, lance.yang,
richard.weiyang, linux-mm, linux-kernel, Vernon Yang
From: Vernon Yang <yanglincheng@kylinos.cn>
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@kylinos.cn>
---
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
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] mm: khugepaged: simplify scanning progress in pmd
2026-02-26 8:13 [PATCH] mm: khugepaged: simplify scanning progress in pmd Vernon Yang
@ 2026-02-26 8:42 ` David Hildenbrand (Arm)
2026-02-26 9:57 ` Vernon Yang
0 siblings, 1 reply; 4+ messages in thread
From: David Hildenbrand (Arm) @ 2026-02-26 8:42 UTC (permalink / raw)
To: Vernon Yang, akpm
Cc: lorenzo.stoakes, ziy, dev.jain, baohua, lance.yang,
richard.weiyang, linux-mm, linux-kernel, Vernon Yang
On 2/26/26 09:13, Vernon Yang wrote:
> From: Vernon Yang <yanglincheng@kylinos.cn>
>
> 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@kylinos.cn>
> ---
We should really squash that into the original patch and revisit it.
Because I think we might be able to do even better.
Could we just switch to "cc->progress" like so (modified original patch):
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 4d7baf220ad9..5d67e5e60ece 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -68,7 +68,10 @@ enum scan_result {
static struct task_struct *khugepaged_thread __read_mostly;
static DEFINE_MUTEX(khugepaged_mutex);
-/* default scan 8*HPAGE_PMD_NR ptes (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;
static unsigned int khugepaged_full_scans;
@@ -100,6 +103,9 @@ struct collapse_control {
/* Num pages scanned per node */
u32 node_load[MAX_NUMNODES];
+ /* Num pages scanned (see khugepaged_pages_to_scan). */
+ unsigned int progress;
+
/* nodemask for allocation fallback */
nodemask_t alloc_nmask;
};
@@ -1247,19 +1253,24 @@ static enum scan_result hpage_collapse_scan_pmd(struct mm_struct *mm,
VM_BUG_ON(start_addr & ~HPAGE_PMD_MASK);
result = find_pmd_or_thp_or_none(mm, start_addr, &pmd);
- if (result != SCAN_SUCCEED)
+ if (result != SCAN_SUCCEED) {
+ cc->progress++;
goto out;
+ }
memset(cc->node_load, 0, sizeof(cc->node_load));
nodes_clear(cc->alloc_nmask);
pte = pte_offset_map_lock(mm, pmd, start_addr, &ptl);
if (!pte) {
+ cc->progress++;
result = SCAN_NO_PTE_TABLE;
goto out;
}
for (addr = start_addr, _pte = pte; _pte < pte + HPAGE_PMD_NR;
_pte++, addr += PAGE_SIZE) {
+ cc->progress++;
+
pte_t pteval = ptep_get(_pte);
if (pte_none_or_zero(pteval)) {
++none_or_zero;
@@ -2370,6 +2381,10 @@ static enum scan_result hpage_collapse_scan_file(struct mm_struct *mm, unsigned
}
}
rcu_read_unlock();
+ if (result == SCAN_PTE_MAPPED_HUGEPAGE)
+ cc->progress++;
+ else
+ cc->progress += HPAGE_PMD_NR;
if (result == SCAN_SUCCEED) {
if (cc->is_khugepaged &&
@@ -2385,8 +2400,8 @@ static enum scan_result hpage_collapse_scan_file(struct mm_struct *mm, unsigned
return result;
}
-static unsigned int khugepaged_scan_mm_slot(unsigned int pages, enum scan_result *result,
- struct collapse_control *cc)
+static void khugepaged_scan_mm_slot(unsigned int progress_max,
+ enum scan_result *result, struct collapse_control *cc)
__releases(&khugepaged_mm_lock)
__acquires(&khugepaged_mm_lock)
{
@@ -2394,9 +2409,7 @@ 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;
- VM_BUG_ON(!pages);
lockdep_assert_held(&khugepaged_mm_lock);
*result = SCAN_FAIL;
@@ -2419,7 +2432,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, enum scan_result
if (unlikely(!mmap_read_trylock(mm)))
goto breakouterloop_mmap_lock;
- progress++;
+ cc->progress++;
if (unlikely(hpage_collapse_test_exit_or_disable(mm)))
goto breakouterloop;
@@ -2429,17 +2442,17 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, enum scan_result
cond_resched();
if (unlikely(hpage_collapse_test_exit_or_disable(mm))) {
- progress++;
+ cc->progress++;
break;
}
if (!thp_vma_allowable_order(vma, vma->vm_flags, TVA_KHUGEPAGED, PMD_ORDER)) {
- progress++;
+ cc->progress++;
continue;
}
hstart = round_up(vma->vm_start, HPAGE_PMD_SIZE);
hend = round_down(vma->vm_end, HPAGE_PMD_SIZE);
if (khugepaged_scan.address > hend) {
- progress++;
+ cc->progress++;
continue;
}
if (khugepaged_scan.address < hstart)
@@ -2486,7 +2499,6 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, enum scan_result
/* move to next address */
khugepaged_scan.address += HPAGE_PMD_SIZE;
- progress += HPAGE_PMD_NR;
if (!mmap_locked)
/*
* We released mmap_lock so break loop. Note
@@ -2496,7 +2508,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, enum scan_result
* correct result back to caller.
*/
goto breakouterloop_mmap_lock;
- if (progress >= pages)
+ if (cc->progress >= progress_max)
goto breakouterloop;
}
}
@@ -2527,9 +2539,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, enum scan_result
collect_mm_slot(slot);
}
- trace_mm_khugepaged_scan(mm, progress, khugepaged_scan.mm_slot == NULL);
-
- return progress;
+ trace_mm_khugepaged_scan(mm, cc->progress, khugepaged_scan.mm_slot == NULL);
}
static int khugepaged_has_work(void)
@@ -2545,13 +2555,14 @@ static int khugepaged_wait_event(void)
static void khugepaged_do_scan(struct collapse_control *cc)
{
- unsigned int progress = 0, pass_through_head = 0;
- unsigned int pages = READ_ONCE(khugepaged_pages_to_scan);
+ const unsigned int progress_max = READ_ONCE(khugepaged_pages_to_scan);
+ unsigned int pass_through_head = 0;
bool wait = true;
enum scan_result result = SCAN_SUCCEED;
lru_add_drain_all();
+ cc->progress = 0;
while (true) {
cond_resched();
@@ -2563,13 +2574,12 @@ static void khugepaged_do_scan(struct collapse_control *cc)
pass_through_head++;
if (khugepaged_has_work() &&
pass_through_head < 2)
- progress += khugepaged_scan_mm_slot(pages - progress,
- &result, cc);
+ khugepaged_scan_mm_slot(progress_max, &result, cc);
else
- progress = pages;
+ cc->progress = progress_max;
spin_unlock(&khugepaged_mm_lock);
- if (progress >= pages)
+ if (cc->progress >= progress_max)
break;
if (result == SCAN_ALLOC_HUGE_PAGE_FAIL) {
--
2.43.0
--
Cheers,
David
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] mm: khugepaged: simplify scanning progress in pmd
2026-02-26 8:42 ` David Hildenbrand (Arm)
@ 2026-02-26 9:57 ` Vernon Yang
2026-02-26 10:01 ` David Hildenbrand (Arm)
0 siblings, 1 reply; 4+ messages in thread
From: Vernon Yang @ 2026-02-26 9:57 UTC (permalink / raw)
To: David Hildenbrand (Arm)
Cc: akpm, lorenzo.stoakes, ziy, dev.jain, baohua, lance.yang,
richard.weiyang, linux-mm, linux-kernel, Vernon Yang
On Thu, Feb 26, 2026 at 09:42:41AM +0100, David Hildenbrand (Arm) wrote:
> On 2/26/26 09:13, Vernon Yang wrote:
> > From: Vernon Yang <yanglincheng@kylinos.cn>
> >
> > 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@kylinos.cn>
> > ---
>
> We should really squash that into the original patch and revisit it.
Yes, squashing this patch into the original patch makes the git commit
log clearer.
> Because I think we might be able to do even better.
>
> Could we just switch to "cc->progress" like so (modified original patch):
>
>
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 4d7baf220ad9..5d67e5e60ece 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -68,7 +68,10 @@ enum scan_result {
> static struct task_struct *khugepaged_thread __read_mostly;
> static DEFINE_MUTEX(khugepaged_mutex);
>
> -/* default scan 8*HPAGE_PMD_NR ptes (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;
> static unsigned int khugepaged_full_scans;
> @@ -100,6 +103,9 @@ struct collapse_control {
> /* Num pages scanned per node */
> u32 node_load[MAX_NUMNODES];
>
> + /* Num pages scanned (see khugepaged_pages_to_scan). */
> + unsigned int progress;
> +
> /* nodemask for allocation fallback */
> nodemask_t alloc_nmask;
> };
> @@ -1247,19 +1253,24 @@ static enum scan_result hpage_collapse_scan_pmd(struct mm_struct *mm,
> VM_BUG_ON(start_addr & ~HPAGE_PMD_MASK);
>
> result = find_pmd_or_thp_or_none(mm, start_addr, &pmd);
> - if (result != SCAN_SUCCEED)
> + if (result != SCAN_SUCCEED) {
> + cc->progress++;
> goto out;
> + }
>
> memset(cc->node_load, 0, sizeof(cc->node_load));
> nodes_clear(cc->alloc_nmask);
> pte = pte_offset_map_lock(mm, pmd, start_addr, &ptl);
> if (!pte) {
> + cc->progress++;
> result = SCAN_NO_PTE_TABLE;
> goto out;
> }
>
> for (addr = start_addr, _pte = pte; _pte < pte + HPAGE_PMD_NR;
> _pte++, addr += PAGE_SIZE) {
> + cc->progress++;
> +
> pte_t pteval = ptep_get(_pte);
> if (pte_none_or_zero(pteval)) {
> ++none_or_zero;
> @@ -2370,6 +2381,10 @@ static enum scan_result hpage_collapse_scan_file(struct mm_struct *mm, unsigned
> }
> }
> rcu_read_unlock();
> + if (result == SCAN_PTE_MAPPED_HUGEPAGE)
> + cc->progress++;
> + else
> + cc->progress += HPAGE_PMD_NR;
>
> if (result == SCAN_SUCCEED) {
> if (cc->is_khugepaged &&
> @@ -2385,8 +2400,8 @@ static enum scan_result hpage_collapse_scan_file(struct mm_struct *mm, unsigned
> return result;
> }
>
> -static unsigned int khugepaged_scan_mm_slot(unsigned int pages, enum scan_result *result,
> - struct collapse_control *cc)
> +static void khugepaged_scan_mm_slot(unsigned int progress_max,
> + enum scan_result *result, struct collapse_control *cc)
> __releases(&khugepaged_mm_lock)
> __acquires(&khugepaged_mm_lock)
> {
> @@ -2394,9 +2409,7 @@ 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;
>
> - VM_BUG_ON(!pages);
> lockdep_assert_held(&khugepaged_mm_lock);
> *result = SCAN_FAIL;
>
> @@ -2419,7 +2432,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, enum scan_result
> if (unlikely(!mmap_read_trylock(mm)))
> goto breakouterloop_mmap_lock;
>
> - progress++;
> + cc->progress++;
> if (unlikely(hpage_collapse_test_exit_or_disable(mm)))
> goto breakouterloop;
>
> @@ -2429,17 +2442,17 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, enum scan_result
>
> cond_resched();
> if (unlikely(hpage_collapse_test_exit_or_disable(mm))) {
> - progress++;
> + cc->progress++;
> break;
> }
> if (!thp_vma_allowable_order(vma, vma->vm_flags, TVA_KHUGEPAGED, PMD_ORDER)) {
> - progress++;
> + cc->progress++;
> continue;
> }
> hstart = round_up(vma->vm_start, HPAGE_PMD_SIZE);
> hend = round_down(vma->vm_end, HPAGE_PMD_SIZE);
> if (khugepaged_scan.address > hend) {
> - progress++;
> + cc->progress++;
> continue;
> }
> if (khugepaged_scan.address < hstart)
> @@ -2486,7 +2499,6 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, enum scan_result
>
> /* move to next address */
> khugepaged_scan.address += HPAGE_PMD_SIZE;
> - progress += HPAGE_PMD_NR;
> if (!mmap_locked)
> /*
> * We released mmap_lock so break loop. Note
> @@ -2496,7 +2508,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, enum scan_result
> * correct result back to caller.
> */
> goto breakouterloop_mmap_lock;
> - if (progress >= pages)
> + if (cc->progress >= progress_max)
> goto breakouterloop;
> }
> }
> @@ -2527,9 +2539,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, enum scan_result
> collect_mm_slot(slot);
> }
>
> - trace_mm_khugepaged_scan(mm, progress, khugepaged_scan.mm_slot == NULL);
> -
> - return progress;
> + trace_mm_khugepaged_scan(mm, cc->progress, khugepaged_scan.mm_slot == NULL);
> }
>
> static int khugepaged_has_work(void)
> @@ -2545,13 +2555,14 @@ static int khugepaged_wait_event(void)
>
> static void khugepaged_do_scan(struct collapse_control *cc)
> {
> - unsigned int progress = 0, pass_through_head = 0;
> - unsigned int pages = READ_ONCE(khugepaged_pages_to_scan);
> + const unsigned int progress_max = READ_ONCE(khugepaged_pages_to_scan);
> + unsigned int pass_through_head = 0;
> bool wait = true;
> enum scan_result result = SCAN_SUCCEED;
>
> lru_add_drain_all();
>
> + cc->progress = 0;
madvise(MADV_COLLAPSE) is missing the initialization of "cc->progress"
because "cc = kmalloc_obj(*cc)". We need to manually initialize it in
madvise_collapse().
LGTM, I will submit v2 with this patch and squashed into the original
patch.
--
Cheers,
Vernon
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] mm: khugepaged: simplify scanning progress in pmd
2026-02-26 9:57 ` Vernon Yang
@ 2026-02-26 10:01 ` David Hildenbrand (Arm)
0 siblings, 0 replies; 4+ messages in thread
From: David Hildenbrand (Arm) @ 2026-02-26 10:01 UTC (permalink / raw)
To: Vernon Yang
Cc: akpm, lorenzo.stoakes, ziy, dev.jain, baohua, lance.yang,
richard.weiyang, linux-mm, linux-kernel, Vernon Yang
>>
>> static int khugepaged_has_work(void)
>> @@ -2545,13 +2555,14 @@ static int khugepaged_wait_event(void)
>>
>> static void khugepaged_do_scan(struct collapse_control *cc)
>> {
>> - unsigned int progress = 0, pass_through_head = 0;
>> - unsigned int pages = READ_ONCE(khugepaged_pages_to_scan);
>> + const unsigned int progress_max = READ_ONCE(khugepaged_pages_to_scan);
>> + unsigned int pass_through_head = 0;
>> bool wait = true;
>> enum scan_result result = SCAN_SUCCEED;
>>
>> lru_add_drain_all();
>>
>> + cc->progress = 0;
>
> madvise(MADV_COLLAPSE) is missing the initialization of "cc->progress"
> because "cc = kmalloc_obj(*cc)". We need to manually initialize it in
> madvise_collapse().
Right, although it wouldn't matter right now, because nobody would be
reading the value.
It's really weird that cc is not simply completely zeroed out in
madvise_collapse().
--
Cheers,
David
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2026-02-26 10:01 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2026-02-26 8:13 [PATCH] mm: khugepaged: simplify scanning progress in pmd Vernon Yang
2026-02-26 8:42 ` David Hildenbrand (Arm)
2026-02-26 9:57 ` Vernon Yang
2026-02-26 10:01 ` David Hildenbrand (Arm)
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox