On 10.02.25 07:32, Shivank Garg wrote:
From: Shivansh Dhiman <shivansh.dhiman@xxxxxxx>
Add NUMA mempolicy support to the filemap allocation path by introducing
new APIs that take a mempolicy argument:
- filemap_grab_folio_mpol()
- filemap_alloc_folio_mpol()
- __filemap_get_folio_mpol()
These APIs allow callers to specify a NUMA policy during page cache
allocations, enabling fine-grained control over memory placement. This is
particularly needed by KVM when using guest-memfd memory backends, where
the guest memory needs to be allocated according to the NUMA policy
specified by VMM.
shmem handles this using custom shmem_alloc_folio()->folio_alloc_mpol().
I'm curious, is there
(1) A way to make shmem also use this new API?
(2) Handle it in guest_memfd manually, like shmem does?
The existing non-mempolicy APIs remain unchanged and continue to use the
default allocation behavior.
Signed-off-by: Shivansh Dhiman <shivansh.dhiman@xxxxxxx>
Signed-off-by: Shivank Garg <shivankg@xxxxxxx>
---
include/linux/pagemap.h | 40 ++++++++++++++++++++++++++++++++++++++++
mm/filemap.c | 30 +++++++++++++++++++++++++-----
2 files changed, 65 insertions(+), 5 deletions(-)
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 47bfc6b1b632..4ae7fa63cb26 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -662,15 +662,25 @@ static inline void *detach_page_private(struct page *page)
#ifdef CONFIG_NUMA
struct folio *filemap_alloc_folio_noprof(gfp_t gfp, unsigned int order);
+struct folio *filemap_alloc_folio_mpol_noprof(gfp_t gfp, unsigned int order,
+ struct mempolicy *mpol);
Two tabs indent on second parameter line, please.
#else
static inline struct folio *filemap_alloc_folio_noprof(gfp_t gfp, unsigned int order)
{
return folio_alloc_noprof(gfp, order);
}
+static inline struct folio *filemap_alloc_folio_mpol_noprof(gfp_t gfp,
+ unsigned int order,
+ struct mempolicy *mpol)
+{
+ return filemap_alloc_folio_noprof(gfp, order);
+}
Dito.
#endif
#define filemap_alloc_folio(...) \
alloc_hooks(filemap_alloc_folio_noprof(__VA_ARGS__))
+#define filemap_alloc_folio_mpol(...) \
+ alloc_hooks(filemap_alloc_folio_mpol_noprof(__VA_ARGS__))
static inline struct page *__page_cache_alloc(gfp_t gfp)
{
@@ -762,6 +772,8 @@ static inline fgf_t fgf_set_order(size_t size)
void *filemap_get_entry(struct address_space *mapping, pgoff_t index);
struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
fgf_t fgp_flags, gfp_t gfp);
+struct folio *__filemap_get_folio_mpol(struct address_space *mapping,
+ pgoff_t index, fgf_t fgp_flags, gfp_t gfp, struct mempolicy *mpol);
struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index,
fgf_t fgp_flags, gfp_t gfp);
@@ -820,6 +832,34 @@ static inline struct folio *filemap_grab_folio(struct address_space *mapping,
mapping_gfp_mask(mapping));
}
+/**
+ * filemap_grab_folio_mpol - grab a folio from the page cache
+ * @mapping: The address space to search
+ * @index: The page index
+ * @mpol: The mempolicy to apply
"The mempolicy to apply when allocating a new folio." ?
+ *
+ * Same as filemap_grab_folio(), except that it allocates the folio using
+ * given memory policy.
+ *
+ * Return: A found or created folio. ERR_PTR(-ENOMEM) if no folio is found
+ * and failed to create a folio.
+ */
+#ifdef CONFIG_NUMA
+static inline struct folio *filemap_grab_folio_mpol(struct address_space *mapping,
+ pgoff_t index, struct mempolicy *mpol)
+{
+ return __filemap_get_folio_mpol(mapping, index,
+ FGP_LOCK | FGP_ACCESSED | FGP_CREAT,
+ mapping_gfp_mask(mapping), mpol);
+}
+#else
+static inline struct folio *filemap_grab_folio_mpol(struct address_space *mapping,
+ pgoff_t index, struct mempolicy *mpol)
+{
+ return filemap_grab_folio(mapping, index);
+}
+#endif /* CONFIG_NUMA */
+
/**
* find_get_page - find and get a page reference
* @mapping: the address_space to search
diff --git a/mm/filemap.c b/mm/filemap.c
index 804d7365680c..c5ea32702774 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1001,8 +1001,13 @@ int filemap_add_folio(struct address_space *mapping, struct folio *folio,
EXPORT_SYMBOL_GPL(filemap_add_folio);
#ifdef CONFIG_NUMA
-struct folio *filemap_alloc_folio_noprof(gfp_t gfp, unsigned int order)
+struct folio *filemap_alloc_folio_mpol_noprof(gfp_t gfp, unsigned int order,
+ struct mempolicy *mpol)
{
+ if (mpol)
+ return folio_alloc_mpol_noprof(gfp, order, mpol,
+ NO_INTERLEAVE_INDEX, numa_node_id());
+
This should go below the variable declaration. (and indentation on
second parameter line should align with the first parameter)
int n;
struct folio *folio;
@@ -1018,6 +1023,12 @@ struct folio *filemap_alloc_folio_noprof(gfp_t gfp, unsigned int order)
}
return folio_alloc_noprof(gfp, order);
}
+EXPORT_SYMBOL(filemap_alloc_folio_mpol_noprof);
+
+struct folio *filemap_alloc_folio_noprof(gfp_t gfp, unsigned int order)
+{
+ return filemap_alloc_folio_mpol_noprof(gfp, order, NULL);
+}
EXPORT_SYMBOL(filemap_alloc_folio_noprof);
#endif
@@ -1881,11 +1892,12 @@ void *filemap_get_entry(struct address_space *mapping, pgoff_t index)
}
/**
- * __filemap_get_folio - Find and get a reference to a folio.
+ * __filemap_get_folio_mpol - Find and get a reference to a folio.
* @mapping: The address_space to search.
* @index: The page index.
* @fgp_flags: %FGP flags modify how the folio is returned.
* @gfp: Memory allocation flags to use if %FGP_CREAT is specified.
+ * @mpol: The mempolicy to apply.
"The mempolicy to apply when allocating a new folio." ?
*
* Looks up the page cache entry at @mapping & @index.
*
@@ -1896,8 +1908,8 @@ void *filemap_get_entry(struct address_space *mapping, pgoff_t index)
*
* Return: The found folio or an ERR_PTR() otherwise.
*/
-struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
- fgf_t fgp_flags, gfp_t gfp)
+struct folio *__filemap_get_folio_mpol(struct address_space *mapping, pgoff_t index,
+ fgf_t fgp_flags, gfp_t gfp, struct mempolicy *mpol)
{
struct folio *folio;
@@ -1967,7 +1979,7 @@ struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
err = -ENOMEM;
if (order > min_order)
alloc_gfp |= __GFP_NORETRY | __GFP_NOWARN;
- folio = filemap_alloc_folio(alloc_gfp, order);
+ folio = filemap_alloc_folio_mpol(alloc_gfp, order, mpol);
if (!folio)
continue;
@@ -2003,6 +2015,14 @@ struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
folio_clear_dropbehind(folio);
return folio;
}
+EXPORT_SYMBOL(__filemap_get_folio_mpol);
+
+struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
+ fgf_t fgp_flags, gfp_t gfp)
+{
+ return __filemap_get_folio_mpol(mapping, index,
+ fgp_flags, gfp, NULL);
+}
EXPORT_SYMBOL(__filemap_get_folio);
static inline struct folio *find_get_entry(struct xa_state *xas, pgoff_t max,
For guest_memfd, where pages are un-movable and un-swappable, the memory
policy will never change later.
shmem seems to handle the swap-in case, because it keeps care of
allocating pages in that case itself.
For ordinary pagecache pages (movable), page migration would likely not
be aware of the specified mpol; I assume the same applies to shmem?
alloc_migration_target() seems to prefer the current nid (nid =
folio_nid(src)), but apart from that, does not lookup any mempolicy.
compaction likely handles this by comapcting within a node/zone.
Maybe migration to the right target node on misplacement is handled on a
higher level lagter (numa hinting faults -> migrate_misplaced_folio).
Likely at least for anon memory, not sure about unmapped shmem.
--
Cheers,
David / dhildenb
