The khugepaged daemon and madvise_collapse have two different
implementations that do almost the same thing.
Create khugepaged_collapse_single_pmd to increase code
reuse and create an entry point for future khugepaged changes.
Refactor madvise_collapse and khugepaged_scan_mm_slot to use
the new khugepaged_collapse_single_pmd function.
Signed-off-by: Nico Pache <npache@redhat.com>
---
mm/khugepaged.c | 96 +++++++++++++++++++++++++------------------------
1 file changed, 50 insertions(+), 46 deletions(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 5f0be134141e..46faee67378b 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -2365,6 +2365,52 @@ static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr,
}
#endif
+/*
+ * Try to collapse a single PMD starting at a PMD aligned addr, and return
+ * the results.
+ */
+static int khugepaged_collapse_single_pmd(unsigned long addr, struct mm_struct *mm,
+ struct vm_area_struct *vma, bool *mmap_locked,
+ struct collapse_control *cc)
+{
+ int result = SCAN_FAIL;
+ unsigned long tva_flags = cc->is_khugepaged ? TVA_ENFORCE_SYSFS : 0;
+
+ if (!*mmap_locked) {
+ mmap_read_lock(mm);
+ *mmap_locked = true;
+ }
+
+ if (thp_vma_allowable_order(vma, vma->vm_flags,
+ tva_flags, PMD_ORDER)) {
+ if (IS_ENABLED(CONFIG_SHMEM) && !vma_is_anonymous(vma)) {
+ struct file *file = get_file(vma->vm_file);
+ pgoff_t pgoff = linear_page_index(vma, addr);
+
+ mmap_read_unlock(mm);
+ *mmap_locked = false;
+ result = hpage_collapse_scan_file(mm, addr, file, pgoff,
+ cc);
+ fput(file);
+ if (result == SCAN_PTE_MAPPED_HUGEPAGE) {
+ mmap_read_lock(mm);
+ if (hpage_collapse_test_exit_or_disable(mm))
+ goto end;
+ result = collapse_pte_mapped_thp(mm, addr,
+ !cc->is_khugepaged);
+ mmap_read_unlock(mm);
+ }
+ } else {
+ result = hpage_collapse_scan_pmd(mm, vma, addr,
+ mmap_locked, cc);
+ }
+ if (result == SCAN_SUCCEED || result == SCAN_PMD_MAPPED)
+ ++khugepaged_pages_collapsed;
+ }
+end:
+ return result;
+}
+
static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
struct collapse_control *cc)
__releases(&khugepaged_mm_lock)
@@ -2439,33 +2485,9 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
VM_BUG_ON(khugepaged_scan.address < hstart ||
khugepaged_scan.address + HPAGE_PMD_SIZE >
hend);
- if (IS_ENABLED(CONFIG_SHMEM) && !vma_is_anonymous(vma)) {
- struct file *file = get_file(vma->vm_file);
- pgoff_t pgoff = linear_page_index(vma,
- khugepaged_scan.address);
- mmap_read_unlock(mm);
- mmap_locked = false;
- *result = hpage_collapse_scan_file(mm,
- khugepaged_scan.address, file, pgoff, cc);
- fput(file);
- if (*result == SCAN_PTE_MAPPED_HUGEPAGE) {
- mmap_read_lock(mm);
- if (hpage_collapse_test_exit_or_disable(mm))
- goto breakouterloop;
- *result = collapse_pte_mapped_thp(mm,
- khugepaged_scan.address, false);
- if (*result == SCAN_PMD_MAPPED)
- *result = SCAN_SUCCEED;
- mmap_read_unlock(mm);
- }
- } else {
- *result = hpage_collapse_scan_pmd(mm, vma,
- khugepaged_scan.address, &mmap_locked, cc);
- }
-
- if (*result == SCAN_SUCCEED)
- ++khugepaged_pages_collapsed;
+ *result = khugepaged_collapse_single_pmd(khugepaged_scan.address,
+ mm, vma, &mmap_locked, cc);
/* move to next address */
khugepaged_scan.address += HPAGE_PMD_SIZE;
@@ -2785,36 +2807,18 @@ int madvise_collapse(struct vm_area_struct *vma, struct vm_area_struct **prev,
mmap_assert_locked(mm);
memset(cc->node_load, 0, sizeof(cc->node_load));
nodes_clear(cc->alloc_nmask);
- if (IS_ENABLED(CONFIG_SHMEM) && !vma_is_anonymous(vma)) {
- struct file *file = get_file(vma->vm_file);
- pgoff_t pgoff = linear_page_index(vma, addr);
- mmap_read_unlock(mm);
- mmap_locked = false;
- result = hpage_collapse_scan_file(mm, addr, file, pgoff,
- cc);
- fput(file);
- } else {
- result = hpage_collapse_scan_pmd(mm, vma, addr,
- &mmap_locked, cc);
- }
+ result = khugepaged_collapse_single_pmd(addr, mm, vma, &mmap_locked, cc);
+
if (!mmap_locked)
*prev = NULL; /* Tell caller we dropped mmap_lock */
-handle_result:
switch (result) {
case SCAN_SUCCEED:
case SCAN_PMD_MAPPED:
++thps;
break;
case SCAN_PTE_MAPPED_HUGEPAGE:
- BUG_ON(mmap_locked);
- BUG_ON(*prev);
- mmap_read_lock(mm);
- result = collapse_pte_mapped_thp(mm, addr, true);
- mmap_read_unlock(mm);
- goto handle_result;
- /* Whitelisted set of results where continuing OK */
case SCAN_PMD_NULL:
case SCAN_PTE_NON_PRESENT:
case SCAN_PTE_UFFD_WP:
--
2.48.1On 11/02/2025 00:30, Nico Pache wrote:
> The khugepaged daemon and madvise_collapse have two different
> implementations that do almost the same thing.
>
> Create khugepaged_collapse_single_pmd to increase code
> reuse and create an entry point for future khugepaged changes.
>
> Refactor madvise_collapse and khugepaged_scan_mm_slot to use
> the new khugepaged_collapse_single_pmd function.
>
> Signed-off-by: Nico Pache <npache@redhat.com>
> ---
> mm/khugepaged.c | 96 +++++++++++++++++++++++++------------------------
> 1 file changed, 50 insertions(+), 46 deletions(-)
>
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 5f0be134141e..46faee67378b 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -2365,6 +2365,52 @@ static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr,
> }
> #endif
>
> +/*
> + * Try to collapse a single PMD starting at a PMD aligned addr, and return
> + * the results.
> + */
> +static int khugepaged_collapse_single_pmd(unsigned long addr, struct mm_struct *mm,
> + struct vm_area_struct *vma, bool *mmap_locked,
> + struct collapse_control *cc)
nit: given the vma links to the mm is it really neccessary to pass both? Why not
just pass vma?
> +{
> + int result = SCAN_FAIL;
> + unsigned long tva_flags = cc->is_khugepaged ? TVA_ENFORCE_SYSFS : 0;
> +
> + if (!*mmap_locked) {
> + mmap_read_lock(mm);
> + *mmap_locked = true;
> + }
AFAICT, the read lock is always held when khugepaged_collapse_single_pmd() is
called. Perhaps VM_WARN_ON(!*mmap_locked) would be more appropriate?
> +
> + if (thp_vma_allowable_order(vma, vma->vm_flags,
> + tva_flags, PMD_ORDER)) {
> + if (IS_ENABLED(CONFIG_SHMEM) && !vma_is_anonymous(vma)) {
I guess it was like this before, but what's the relevance of CONFIG_SHMEM?
Surely this should work for any file if CONFIG_READ_ONLY_THP_FOR_FS is enabled?
> + struct file *file = get_file(vma->vm_file);
> + pgoff_t pgoff = linear_page_index(vma, addr);
> +
> + mmap_read_unlock(mm);
> + *mmap_locked = false;
> + result = hpage_collapse_scan_file(mm, addr, file, pgoff,
> + cc);
> + fput(file);
> + if (result == SCAN_PTE_MAPPED_HUGEPAGE) {
> + mmap_read_lock(mm);
> + if (hpage_collapse_test_exit_or_disable(mm))
> + goto end;
> + result = collapse_pte_mapped_thp(mm, addr,
> + !cc->is_khugepaged);
> + mmap_read_unlock(mm);
> + }
> + } else {
> + result = hpage_collapse_scan_pmd(mm, vma, addr,
> + mmap_locked, cc);
> + }
> + if (result == SCAN_SUCCEED || result == SCAN_PMD_MAPPED)
> + ++khugepaged_pages_collapsed;
Looks like this counter was previously only incremented for the scan path, not
for the madvise_collapse path. Not sure if that's a problem?
Thanks,
Ryan
> + }
> +end:
> + return result;
> +}
> +
> static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
> struct collapse_control *cc)
> __releases(&khugepaged_mm_lock)
> @@ -2439,33 +2485,9 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
> VM_BUG_ON(khugepaged_scan.address < hstart ||
> khugepaged_scan.address + HPAGE_PMD_SIZE >
> hend);
> - if (IS_ENABLED(CONFIG_SHMEM) && !vma_is_anonymous(vma)) {
> - struct file *file = get_file(vma->vm_file);
> - pgoff_t pgoff = linear_page_index(vma,
> - khugepaged_scan.address);
>
> - mmap_read_unlock(mm);
> - mmap_locked = false;
> - *result = hpage_collapse_scan_file(mm,
> - khugepaged_scan.address, file, pgoff, cc);
> - fput(file);
> - if (*result == SCAN_PTE_MAPPED_HUGEPAGE) {
> - mmap_read_lock(mm);
> - if (hpage_collapse_test_exit_or_disable(mm))
> - goto breakouterloop;
> - *result = collapse_pte_mapped_thp(mm,
> - khugepaged_scan.address, false);
> - if (*result == SCAN_PMD_MAPPED)
> - *result = SCAN_SUCCEED;
> - mmap_read_unlock(mm);
> - }
> - } else {
> - *result = hpage_collapse_scan_pmd(mm, vma,
> - khugepaged_scan.address, &mmap_locked, cc);
> - }
> -
> - if (*result == SCAN_SUCCEED)
> - ++khugepaged_pages_collapsed;
> + *result = khugepaged_collapse_single_pmd(khugepaged_scan.address,
> + mm, vma, &mmap_locked, cc);
>
> /* move to next address */
> khugepaged_scan.address += HPAGE_PMD_SIZE;
> @@ -2785,36 +2807,18 @@ int madvise_collapse(struct vm_area_struct *vma, struct vm_area_struct **prev,
> mmap_assert_locked(mm);
> memset(cc->node_load, 0, sizeof(cc->node_load));
> nodes_clear(cc->alloc_nmask);
> - if (IS_ENABLED(CONFIG_SHMEM) && !vma_is_anonymous(vma)) {
> - struct file *file = get_file(vma->vm_file);
> - pgoff_t pgoff = linear_page_index(vma, addr);
>
> - mmap_read_unlock(mm);
> - mmap_locked = false;
> - result = hpage_collapse_scan_file(mm, addr, file, pgoff,
> - cc);
> - fput(file);
> - } else {
> - result = hpage_collapse_scan_pmd(mm, vma, addr,
> - &mmap_locked, cc);
> - }
> + result = khugepaged_collapse_single_pmd(addr, mm, vma, &mmap_locked, cc);
> +
> if (!mmap_locked)
> *prev = NULL; /* Tell caller we dropped mmap_lock */
>
> -handle_result:
> switch (result) {
> case SCAN_SUCCEED:
> case SCAN_PMD_MAPPED:
> ++thps;
> break;
> case SCAN_PTE_MAPPED_HUGEPAGE:
> - BUG_ON(mmap_locked);
> - BUG_ON(*prev);
> - mmap_read_lock(mm);
> - result = collapse_pte_mapped_thp(mm, addr, true);
> - mmap_read_unlock(mm);
> - goto handle_result;
> - /* Whitelisted set of results where continuing OK */
> case SCAN_PMD_NULL:
> case SCAN_PTE_NON_PRESENT:
> case SCAN_PTE_UFFD_WP:
On Tue, Feb 18, 2025 at 9:26 AM Ryan Roberts <ryan.roberts@arm.com> wrote:
>
> On 11/02/2025 00:30, Nico Pache wrote:
> > The khugepaged daemon and madvise_collapse have two different
> > implementations that do almost the same thing.
> >
> > Create khugepaged_collapse_single_pmd to increase code
> > reuse and create an entry point for future khugepaged changes.
> >
> > Refactor madvise_collapse and khugepaged_scan_mm_slot to use
> > the new khugepaged_collapse_single_pmd function.
> >
> > Signed-off-by: Nico Pache <npache@redhat.com>
> > ---
> > mm/khugepaged.c | 96 +++++++++++++++++++++++++------------------------
> > 1 file changed, 50 insertions(+), 46 deletions(-)
> >
> > diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> > index 5f0be134141e..46faee67378b 100644
> > --- a/mm/khugepaged.c
> > +++ b/mm/khugepaged.c
> > @@ -2365,6 +2365,52 @@ static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr,
> > }
> > #endif
> >
> > +/*
> > + * Try to collapse a single PMD starting at a PMD aligned addr, and return
> > + * the results.
> > + */
> > +static int khugepaged_collapse_single_pmd(unsigned long addr, struct mm_struct *mm,
> > + struct vm_area_struct *vma, bool *mmap_locked,
> > + struct collapse_control *cc)
>
> nit: given the vma links to the mm is it really neccessary to pass both? Why not
> just pass vma?
Ah good point!
>
> > +{
> > + int result = SCAN_FAIL;
> > + unsigned long tva_flags = cc->is_khugepaged ? TVA_ENFORCE_SYSFS : 0;
> > +
> > + if (!*mmap_locked) {
> > + mmap_read_lock(mm);
> > + *mmap_locked = true;
> > + }
>
> AFAICT, the read lock is always held when khugepaged_collapse_single_pmd() is
> called. Perhaps VM_WARN_ON(!*mmap_locked) would be more appropriate?
Hmm, I'm actually not sure why that's there. Its probably left over
from a previous change I was trying a while back.
>
> > +
> > + if (thp_vma_allowable_order(vma, vma->vm_flags,
> > + tva_flags, PMD_ORDER)) {
> > + if (IS_ENABLED(CONFIG_SHMEM) && !vma_is_anonymous(vma)) {
>
> I guess it was like this before, but what's the relevance of CONFIG_SHMEM?
> Surely this should work for any file if CONFIG_READ_ONLY_THP_FOR_FS is enabled?
Yeah I think David brought up a similar point during one of our
meetings. I'm just combining the collapse users, so I'll leave it for
now.
>
> > + struct file *file = get_file(vma->vm_file);
> > + pgoff_t pgoff = linear_page_index(vma, addr);
> > +
> > + mmap_read_unlock(mm);
> > + *mmap_locked = false;
> > + result = hpage_collapse_scan_file(mm, addr, file, pgoff,
> > + cc);
> > + fput(file);
> > + if (result == SCAN_PTE_MAPPED_HUGEPAGE) {
> > + mmap_read_lock(mm);
> > + if (hpage_collapse_test_exit_or_disable(mm))
> > + goto end;
> > + result = collapse_pte_mapped_thp(mm, addr,
> > + !cc->is_khugepaged);
> > + mmap_read_unlock(mm);
> > + }
> > + } else {
> > + result = hpage_collapse_scan_pmd(mm, vma, addr,
> > + mmap_locked, cc);
> > + }
> > + if (result == SCAN_SUCCEED || result == SCAN_PMD_MAPPED)
> > + ++khugepaged_pages_collapsed;
>
> Looks like this counter was previously only incremented for the scan path, not
> for the madvise_collapse path. Not sure if that's a problem?
Yep! Usama noted that too, already fixed in the next version :)
Thanks!
-- Nico
>
> Thanks,
> Ryan
>
> > + }
> > +end:
> > + return result;
> > +}
> > +
> > static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
> > struct collapse_control *cc)
> > __releases(&khugepaged_mm_lock)
> > @@ -2439,33 +2485,9 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
> > VM_BUG_ON(khugepaged_scan.address < hstart ||
> > khugepaged_scan.address + HPAGE_PMD_SIZE >
> > hend);
> > - if (IS_ENABLED(CONFIG_SHMEM) && !vma_is_anonymous(vma)) {
> > - struct file *file = get_file(vma->vm_file);
> > - pgoff_t pgoff = linear_page_index(vma,
> > - khugepaged_scan.address);
> >
> > - mmap_read_unlock(mm);
> > - mmap_locked = false;
> > - *result = hpage_collapse_scan_file(mm,
> > - khugepaged_scan.address, file, pgoff, cc);
> > - fput(file);
> > - if (*result == SCAN_PTE_MAPPED_HUGEPAGE) {
> > - mmap_read_lock(mm);
> > - if (hpage_collapse_test_exit_or_disable(mm))
> > - goto breakouterloop;
> > - *result = collapse_pte_mapped_thp(mm,
> > - khugepaged_scan.address, false);
> > - if (*result == SCAN_PMD_MAPPED)
> > - *result = SCAN_SUCCEED;
> > - mmap_read_unlock(mm);
> > - }
> > - } else {
> > - *result = hpage_collapse_scan_pmd(mm, vma,
> > - khugepaged_scan.address, &mmap_locked, cc);
> > - }
> > -
> > - if (*result == SCAN_SUCCEED)
> > - ++khugepaged_pages_collapsed;
> > + *result = khugepaged_collapse_single_pmd(khugepaged_scan.address,
> > + mm, vma, &mmap_locked, cc);
> >
> > /* move to next address */
> > khugepaged_scan.address += HPAGE_PMD_SIZE;
> > @@ -2785,36 +2807,18 @@ int madvise_collapse(struct vm_area_struct *vma, struct vm_area_struct **prev,
> > mmap_assert_locked(mm);
> > memset(cc->node_load, 0, sizeof(cc->node_load));
> > nodes_clear(cc->alloc_nmask);
> > - if (IS_ENABLED(CONFIG_SHMEM) && !vma_is_anonymous(vma)) {
> > - struct file *file = get_file(vma->vm_file);
> > - pgoff_t pgoff = linear_page_index(vma, addr);
> >
> > - mmap_read_unlock(mm);
> > - mmap_locked = false;
> > - result = hpage_collapse_scan_file(mm, addr, file, pgoff,
> > - cc);
> > - fput(file);
> > - } else {
> > - result = hpage_collapse_scan_pmd(mm, vma, addr,
> > - &mmap_locked, cc);
> > - }
> > + result = khugepaged_collapse_single_pmd(addr, mm, vma, &mmap_locked, cc);
> > +
> > if (!mmap_locked)
> > *prev = NULL; /* Tell caller we dropped mmap_lock */
> >
> > -handle_result:
> > switch (result) {
> > case SCAN_SUCCEED:
> > case SCAN_PMD_MAPPED:
> > ++thps;
> > break;
> > case SCAN_PTE_MAPPED_HUGEPAGE:
> > - BUG_ON(mmap_locked);
> > - BUG_ON(*prev);
> > - mmap_read_lock(mm);
> > - result = collapse_pte_mapped_thp(mm, addr, true);
> > - mmap_read_unlock(mm);
> > - goto handle_result;
> > - /* Whitelisted set of results where continuing OK */
> > case SCAN_PMD_NULL:
> > case SCAN_PTE_NON_PRESENT:
> > case SCAN_PTE_UFFD_WP:
>
On 11/02/2025 00:30, Nico Pache wrote:
> The khugepaged daemon and madvise_collapse have two different
> implementations that do almost the same thing.
>
> Create khugepaged_collapse_single_pmd to increase code
> reuse and create an entry point for future khugepaged changes.
>
> Refactor madvise_collapse and khugepaged_scan_mm_slot to use
> the new khugepaged_collapse_single_pmd function.
>
> Signed-off-by: Nico Pache <npache@redhat.com>
> ---
> mm/khugepaged.c | 96 +++++++++++++++++++++++++------------------------
> 1 file changed, 50 insertions(+), 46 deletions(-)
>
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 5f0be134141e..46faee67378b 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -2365,6 +2365,52 @@ static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr,
> }
> #endif
>
> +/*
> + * Try to collapse a single PMD starting at a PMD aligned addr, and return
> + * the results.
> + */
> +static int khugepaged_collapse_single_pmd(unsigned long addr, struct mm_struct *mm,
> + struct vm_area_struct *vma, bool *mmap_locked,
> + struct collapse_control *cc)
> +{
> + int result = SCAN_FAIL;
> + unsigned long tva_flags = cc->is_khugepaged ? TVA_ENFORCE_SYSFS : 0;
> +
> + if (!*mmap_locked) {
> + mmap_read_lock(mm);
> + *mmap_locked = true;
> + }
> +
> + if (thp_vma_allowable_order(vma, vma->vm_flags,
> + tva_flags, PMD_ORDER)) {
> + if (IS_ENABLED(CONFIG_SHMEM) && !vma_is_anonymous(vma)) {
> + struct file *file = get_file(vma->vm_file);
> + pgoff_t pgoff = linear_page_index(vma, addr);
> +
> + mmap_read_unlock(mm);
> + *mmap_locked = false;
> + result = hpage_collapse_scan_file(mm, addr, file, pgoff,
> + cc);
> + fput(file);
> + if (result == SCAN_PTE_MAPPED_HUGEPAGE) {
> + mmap_read_lock(mm);
> + if (hpage_collapse_test_exit_or_disable(mm))
> + goto end;
> + result = collapse_pte_mapped_thp(mm, addr,
> + !cc->is_khugepaged);
> + mmap_read_unlock(mm);
> + }
> + } else {
> + result = hpage_collapse_scan_pmd(mm, vma, addr,
> + mmap_locked, cc);
> + }
> + if (result == SCAN_SUCCEED || result == SCAN_PMD_MAPPED)
> + ++khugepaged_pages_collapsed;
> + }
> +end:
> + return result;
> +}
> +
> static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
> struct collapse_control *cc)
> __releases(&khugepaged_mm_lock)
> @@ -2439,33 +2485,9 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
> VM_BUG_ON(khugepaged_scan.address < hstart ||
> khugepaged_scan.address + HPAGE_PMD_SIZE >
> hend);
> - if (IS_ENABLED(CONFIG_SHMEM) && !vma_is_anonymous(vma)) {
> - struct file *file = get_file(vma->vm_file);
> - pgoff_t pgoff = linear_page_index(vma,
> - khugepaged_scan.address);
>
> - mmap_read_unlock(mm);
> - mmap_locked = false;
> - *result = hpage_collapse_scan_file(mm,
> - khugepaged_scan.address, file, pgoff, cc);
> - fput(file);
> - if (*result == SCAN_PTE_MAPPED_HUGEPAGE) {
> - mmap_read_lock(mm);
> - if (hpage_collapse_test_exit_or_disable(mm))
> - goto breakouterloop;
> - *result = collapse_pte_mapped_thp(mm,
> - khugepaged_scan.address, false);
> - if (*result == SCAN_PMD_MAPPED)
> - *result = SCAN_SUCCEED;
> - mmap_read_unlock(mm);
> - }
> - } else {
> - *result = hpage_collapse_scan_pmd(mm, vma,
> - khugepaged_scan.address, &mmap_locked, cc);
> - }
> -
> - if (*result == SCAN_SUCCEED)
> - ++khugepaged_pages_collapsed;
> + *result = khugepaged_collapse_single_pmd(khugepaged_scan.address,
> + mm, vma, &mmap_locked, cc);
>
> /* move to next address */
> khugepaged_scan.address += HPAGE_PMD_SIZE;
> @@ -2785,36 +2807,18 @@ int madvise_collapse(struct vm_area_struct *vma, struct vm_area_struct **prev,
> mmap_assert_locked(mm);
> memset(cc->node_load, 0, sizeof(cc->node_load));
> nodes_clear(cc->alloc_nmask);
> - if (IS_ENABLED(CONFIG_SHMEM) && !vma_is_anonymous(vma)) {
> - struct file *file = get_file(vma->vm_file);
> - pgoff_t pgoff = linear_page_index(vma, addr);
>
> - mmap_read_unlock(mm);
> - mmap_locked = false;
> - result = hpage_collapse_scan_file(mm, addr, file, pgoff,
> - cc);
> - fput(file);
> - } else {
> - result = hpage_collapse_scan_pmd(mm, vma, addr,
> - &mmap_locked, cc);
> - }
> + result = khugepaged_collapse_single_pmd(addr, mm, vma, &mmap_locked, cc);
> +
you will be incrementing khugepaged_pages_collapsed at madvise_collapse by calling
khugepaged_collapse_single_pmd which is not correct.
> if (!mmap_locked)
> *prev = NULL; /* Tell caller we dropped mmap_lock */
>
> -handle_result:
> switch (result) {
> case SCAN_SUCCEED:
> case SCAN_PMD_MAPPED:
> ++thps;
> break;
> case SCAN_PTE_MAPPED_HUGEPAGE:
> - BUG_ON(mmap_locked);
> - BUG_ON(*prev);
> - mmap_read_lock(mm);
> - result = collapse_pte_mapped_thp(mm, addr, true);
> - mmap_read_unlock(mm);
> - goto handle_result;
> - /* Whitelisted set of results where continuing OK */
> case SCAN_PMD_NULL:
> case SCAN_PTE_NON_PRESENT:
> case SCAN_PTE_UFFD_WP:
On Mon, Feb 17, 2025 at 10:11 AM Usama Arif <usamaarif642@gmail.com> wrote:
>
>
>
> On 11/02/2025 00:30, Nico Pache wrote:
> > The khugepaged daemon and madvise_collapse have two different
> > implementations that do almost the same thing.
> >
> > Create khugepaged_collapse_single_pmd to increase code
> > reuse and create an entry point for future khugepaged changes.
> >
> > Refactor madvise_collapse and khugepaged_scan_mm_slot to use
> > the new khugepaged_collapse_single_pmd function.
> >
> > Signed-off-by: Nico Pache <npache@redhat.com>
> > ---
> > mm/khugepaged.c | 96 +++++++++++++++++++++++++------------------------
> > 1 file changed, 50 insertions(+), 46 deletions(-)
> >
> > diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> > index 5f0be134141e..46faee67378b 100644
> > --- a/mm/khugepaged.c
> > +++ b/mm/khugepaged.c
> > @@ -2365,6 +2365,52 @@ static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr,
> > }
> > #endif
> >
> > +/*
> > + * Try to collapse a single PMD starting at a PMD aligned addr, and return
> > + * the results.
> > + */
> > +static int khugepaged_collapse_single_pmd(unsigned long addr, struct mm_struct *mm,
> > + struct vm_area_struct *vma, bool *mmap_locked,
> > + struct collapse_control *cc)
> > +{
> > + int result = SCAN_FAIL;
> > + unsigned long tva_flags = cc->is_khugepaged ? TVA_ENFORCE_SYSFS : 0;
> > +
> > + if (!*mmap_locked) {
> > + mmap_read_lock(mm);
> > + *mmap_locked = true;
> > + }
> > +
> > + if (thp_vma_allowable_order(vma, vma->vm_flags,
> > + tva_flags, PMD_ORDER)) {
> > + if (IS_ENABLED(CONFIG_SHMEM) && !vma_is_anonymous(vma)) {
> > + struct file *file = get_file(vma->vm_file);
> > + pgoff_t pgoff = linear_page_index(vma, addr);
> > +
> > + mmap_read_unlock(mm);
> > + *mmap_locked = false;
> > + result = hpage_collapse_scan_file(mm, addr, file, pgoff,
> > + cc);
> > + fput(file);
> > + if (result == SCAN_PTE_MAPPED_HUGEPAGE) {
> > + mmap_read_lock(mm);
> > + if (hpage_collapse_test_exit_or_disable(mm))
> > + goto end;
> > + result = collapse_pte_mapped_thp(mm, addr,
> > + !cc->is_khugepaged);
> > + mmap_read_unlock(mm);
> > + }
> > + } else {
> > + result = hpage_collapse_scan_pmd(mm, vma, addr,
> > + mmap_locked, cc);
> > + }
> > + if (result == SCAN_SUCCEED || result == SCAN_PMD_MAPPED)
> > + ++khugepaged_pages_collapsed;
> > + }
> > +end:
> > + return result;
> > +}
> > +
> > static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
> > struct collapse_control *cc)
> > __releases(&khugepaged_mm_lock)
> > @@ -2439,33 +2485,9 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
> > VM_BUG_ON(khugepaged_scan.address < hstart ||
> > khugepaged_scan.address + HPAGE_PMD_SIZE >
> > hend);
> > - if (IS_ENABLED(CONFIG_SHMEM) && !vma_is_anonymous(vma)) {
> > - struct file *file = get_file(vma->vm_file);
> > - pgoff_t pgoff = linear_page_index(vma,
> > - khugepaged_scan.address);
> >
> > - mmap_read_unlock(mm);
> > - mmap_locked = false;
> > - *result = hpage_collapse_scan_file(mm,
> > - khugepaged_scan.address, file, pgoff, cc);
> > - fput(file);
> > - if (*result == SCAN_PTE_MAPPED_HUGEPAGE) {
> > - mmap_read_lock(mm);
> > - if (hpage_collapse_test_exit_or_disable(mm))
> > - goto breakouterloop;
> > - *result = collapse_pte_mapped_thp(mm,
> > - khugepaged_scan.address, false);
> > - if (*result == SCAN_PMD_MAPPED)
> > - *result = SCAN_SUCCEED;
> > - mmap_read_unlock(mm);
> > - }
> > - } else {
> > - *result = hpage_collapse_scan_pmd(mm, vma,
> > - khugepaged_scan.address, &mmap_locked, cc);
> > - }
> > -
> > - if (*result == SCAN_SUCCEED)
> > - ++khugepaged_pages_collapsed;
> > + *result = khugepaged_collapse_single_pmd(khugepaged_scan.address,
> > + mm, vma, &mmap_locked, cc);
> >
> > /* move to next address */
> > khugepaged_scan.address += HPAGE_PMD_SIZE;
> > @@ -2785,36 +2807,18 @@ int madvise_collapse(struct vm_area_struct *vma, struct vm_area_struct **prev,
> > mmap_assert_locked(mm);
> > memset(cc->node_load, 0, sizeof(cc->node_load));
> > nodes_clear(cc->alloc_nmask);
> > - if (IS_ENABLED(CONFIG_SHMEM) && !vma_is_anonymous(vma)) {
> > - struct file *file = get_file(vma->vm_file);
> > - pgoff_t pgoff = linear_page_index(vma, addr);
> >
> > - mmap_read_unlock(mm);
> > - mmap_locked = false;
> > - result = hpage_collapse_scan_file(mm, addr, file, pgoff,
> > - cc);
> > - fput(file);
> > - } else {
> > - result = hpage_collapse_scan_pmd(mm, vma, addr,
> > - &mmap_locked, cc);
> > - }
> > + result = khugepaged_collapse_single_pmd(addr, mm, vma, &mmap_locked, cc);
> > +
>
> you will be incrementing khugepaged_pages_collapsed at madvise_collapse by calling
> khugepaged_collapse_single_pmd which is not correct.
Ah good catch, Ill add a conditional around the incrementation. Thanks!
>
> > if (!mmap_locked)
> > *prev = NULL; /* Tell caller we dropped mmap_lock */
> >
> > -handle_result:
> > switch (result) {
> > case SCAN_SUCCEED:
> > case SCAN_PMD_MAPPED:
> > ++thps;
> > break;
> > case SCAN_PTE_MAPPED_HUGEPAGE:
> > - BUG_ON(mmap_locked);
> > - BUG_ON(*prev);
> > - mmap_read_lock(mm);
> > - result = collapse_pte_mapped_thp(mm, addr, true);
> > - mmap_read_unlock(mm);
> > - goto handle_result;
> > - /* Whitelisted set of results where continuing OK */
> > case SCAN_PMD_NULL:
> > case SCAN_PTE_NON_PRESENT:
> > case SCAN_PTE_UFFD_WP:
>
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