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mm/khugepaged: rename mthp_present_ptes bitmap to eligible_ptes

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The name says less than the bit means.  A set bit means not only that the
PTE is present, but also that it passed the other checks: uffd,
lazyfree, anonymity, sharing.  The PTE can be considered a collapse
source.

mthp_collapse() then reads the bitmap starting at the PMD order, so the
bitmap is not specific to mTHP either.

Name it for what a set bit means, and update the comments that named it.

No functional change.

Link: https://lore.kernel.org/20261014171145.3292736-4-kas@kernel.org
Signed-off-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Assisted-by: LLM
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Nico Pache <nico.pache@linux.dev>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Usama Arif <usama.arif@linux.dev>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Jann Horn <jannh@google.com>
This commit is contained in:
Kiryl Shutsemau (Meta) 2026-10-14 18:11:36 +01:00 committed by Andrew Morton
parent 47cda827a0
commit d950ec79fc
1 changed files with 16 additions and 16 deletions
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32
mm/khugepaged.c
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@ -115,8 +115,8 @@ struct collapse_control {
/* nodemask for allocation fallback */
nodemask_t alloc_nmask;
/* Each bit represents a single occupied (!none/zero) page. */
DECLARE_BITMAP(mthp_present_ptes, MAX_PTRS_PER_PTE);
/* Each bit marks a PTE the scan accepted as a collapse source */
DECLARE_BITMAP(eligible_ptes, MAX_PTRS_PER_PTE);
};
/**
@ -627,7 +627,7 @@ static void collapse_control_init_scan(struct collapse_control *cc)
{
memset(cc->node_load, 0, sizeof(cc->node_load));
nodes_clear(cc->alloc_nmask);
bitmap_zero(cc->mthp_present_ptes, MAX_PTRS_PER_PTE);
bitmap_zero(cc->eligible_ptes, MAX_PTRS_PER_PTE);
}
static void release_pte_folio(struct folio *folio)
@ -1512,15 +1512,15 @@ static unsigned int max_order_from_offset(unsigned int offset)
* mthp_collapse() consumes the bitmap that is generated during
* collapse_scan_pmd() to determine what regions and mTHP orders fit best.
*
* Each bit in cc->mthp_present_ptes represents a single occupied (!none/zero)
* page. We start at the PMD order and check if it is eligible for collapse;
* Each bit in cc->eligible_ptes marks a PTE the scan accepted as a collapse
* source. We start at the PMD order and check if it is eligible for collapse;
* if not, we check the left and right halves of the PTE page table we are
* examining at a lower order.
*
* For each of these, we determine how many PTE entries are occupied in the
* range of PTE entries we propose to collapse, then we compare this to a
* threshold number of PTE entries which would need to be occupied for a
* collapse to be permitted at that order (accounting for max_ptes_none).
* For each of these, we count the eligible PTEs in the range we propose to
* collapse, then we compare this to the number of eligible PTEs the range
* would need for a collapse to be permitted at that order (accounting for
* max_ptes_none).
*
* If a collapse is permitted, we attempt to collapse the PTE range into a
* mTHP.
@ -1529,7 +1529,7 @@ static enum scan_result mthp_collapse(struct mm_struct *mm,
unsigned long address, int referenced, int unmapped,
struct collapse_control *cc, unsigned long enabled_orders)
{
unsigned int nr_occupied_ptes, nr_ptes, max_ptes_none;
unsigned int nr_eligible_ptes, nr_ptes, max_ptes_none;
enum scan_result last_result = SCAN_FAIL;
int collapsed = 0;
bool alloc_failed = false;
@ -1544,18 +1544,18 @@ static enum scan_result mthp_collapse(struct mm_struct *mm,
goto next_order;
max_ptes_none = collapse_max_ptes_none(cc, NULL, order);
nr_occupied_ptes = bitmap_weight_from(cc->mthp_present_ptes, offset,
nr_eligible_ptes = bitmap_weight_from(cc->eligible_ptes, offset,
offset + nr_ptes);
/*
* Swap PTEs accepted during the scan are counted in @unmapped,
* not in the present-PTE bitmap. Account them for the PMD-order
* not in cc->eligible_ptes. Account them for the PMD-order
* candidate.
*/
if (is_pmd_order(order))
nr_occupied_ptes += unmapped;
nr_eligible_ptes += unmapped;
if (nr_occupied_ptes >= nr_ptes - max_ptes_none) {
if (nr_eligible_ptes >= nr_ptes - max_ptes_none) {
enum scan_result ret;
collapse_address = address + offset * PAGE_SIZE;
@ -1761,8 +1761,8 @@ static enum scan_result collapse_scan_pmd(struct mm_struct *mm,
}
}
/* Set bit for occupied pages */
__set_bit(i, cc->mthp_present_ptes);
/* The scan accepted this PTE as a collapse source */
__set_bit(i, cc->eligible_ptes);
/*
* Record which node the original page is from and save this
* information to cc->node_load[].