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Message-ID: <20250818064615.505641-2-rppt@kernel.org>
Date: Mon, 18 Aug 2025 09:46:12 +0300
From: Mike Rapoport <rppt@...nel.org>
To: linux-mm@...ck.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Bill Wendling <morbo@...gle.com>,
Daniel Jordan <daniel.m.jordan@...cle.com>,
Justin Stitt <justinstitt@...gle.com>,
Michael Ellerman <mpe@...erman.id.au>,
Miguel Ojeda <ojeda@...nel.org>,
Mike Rapoport <rppt@...nel.org>,
Nathan Chancellor <nathan@...nel.org>,
Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
linux-kernel@...r.kernel.org,
llvm@...ts.linux.dev
Subject: [PATCH 1/4] mm/mm_init: use deferred_init_memmap_chunk() in deferred_grow_zone()
From: "Mike Rapoport (Microsoft)" <rppt@...nel.org>
deferred_grow_zone() initializes one or more sections in the memory map
if buddy runs out of initialized struct pages when
CONFIG_DEFERRED_STRUCT_PAGE_INIT is enabled.
It loops through memblock regions and initializes and frees pages in
MAX_ORDER_NR_PAGES chunks.
Essentially the same loop is implemented in deferred_init_memmap_chunk(),
the only actual difference is that deferred_init_memmap_chunk() does not
count initialized pages.
Make deferred_init_memmap_chunk() count the initialized pages and return
their number, wrap it with deferred_init_memmap_job() for multithreaded
initialization with padata_do_multithreaded() and replace open-coded
initialization of struct pages in deferred_grow_zone() with a call to
deferred_init_memmap_chunk().
Signed-off-by: Mike Rapoport (Microsoft) <rppt@...nel.org>
---
mm/mm_init.c | 65 ++++++++++++++++++++++++++--------------------------
1 file changed, 32 insertions(+), 33 deletions(-)
diff --git a/mm/mm_init.c b/mm/mm_init.c
index 5c21b3af216b..81809b83814b 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -2134,12 +2134,12 @@ deferred_init_maxorder(u64 *i, struct zone *zone, unsigned long *start_pfn,
return nr_pages;
}
-static void __init
+static unsigned long __init
deferred_init_memmap_chunk(unsigned long start_pfn, unsigned long end_pfn,
- void *arg)
+ struct zone *zone)
{
+ unsigned long nr_pages = 0;
unsigned long spfn, epfn;
- struct zone *zone = arg;
u64 i = 0;
deferred_init_mem_pfn_range_in_zone(&i, zone, &spfn, &epfn, start_pfn);
@@ -2149,9 +2149,20 @@ deferred_init_memmap_chunk(unsigned long start_pfn, unsigned long end_pfn,
* we can avoid introducing any issues with the buddy allocator.
*/
while (spfn < end_pfn) {
- deferred_init_maxorder(&i, zone, &spfn, &epfn);
+ nr_pages += deferred_init_maxorder(&i, zone, &spfn, &epfn);
cond_resched();
}
+
+ return nr_pages;
+}
+
+static void __init
+deferred_init_memmap_job(unsigned long start_pfn, unsigned long end_pfn,
+ void *arg)
+{
+ struct zone *zone = arg;
+
+ deferred_init_memmap_chunk(start_pfn, end_pfn, zone);
}
static unsigned int __init
@@ -2204,7 +2215,7 @@ static int __init deferred_init_memmap(void *data)
while (deferred_init_mem_pfn_range_in_zone(&i, zone, &spfn, &epfn, first_init_pfn)) {
first_init_pfn = ALIGN(epfn, PAGES_PER_SECTION);
struct padata_mt_job job = {
- .thread_fn = deferred_init_memmap_chunk,
+ .thread_fn = deferred_init_memmap_job,
.fn_arg = zone,
.start = spfn,
.size = first_init_pfn - spfn,
@@ -2240,12 +2251,11 @@ static int __init deferred_init_memmap(void *data)
*/
bool __init deferred_grow_zone(struct zone *zone, unsigned int order)
{
- unsigned long nr_pages_needed = ALIGN(1 << order, PAGES_PER_SECTION);
+ unsigned long nr_pages_needed = SECTION_ALIGN_UP(1 << order);
pg_data_t *pgdat = zone->zone_pgdat;
unsigned long first_deferred_pfn = pgdat->first_deferred_pfn;
unsigned long spfn, epfn, flags;
unsigned long nr_pages = 0;
- u64 i = 0;
/* Only the last zone may have deferred pages */
if (zone_end_pfn(zone) != pgdat_end_pfn(pgdat))
@@ -2262,37 +2272,26 @@ bool __init deferred_grow_zone(struct zone *zone, unsigned int order)
return true;
}
- /* If the zone is empty somebody else may have cleared out the zone */
- if (!deferred_init_mem_pfn_range_in_zone(&i, zone, &spfn, &epfn,
- first_deferred_pfn)) {
- pgdat->first_deferred_pfn = ULONG_MAX;
- pgdat_resize_unlock(pgdat, &flags);
- /* Retry only once. */
- return first_deferred_pfn != ULONG_MAX;
+ /*
+ * Initialize at least nr_pages_needed in section chunks.
+ * If a section has less free memory than nr_pages_needed, the next
+ * section will be also initalized.
+ * Note, that it still does not guarantee that allocation of order can
+ * be satisfied if the sections are fragmented because of memblock
+ * allocations.
+ */
+ for (spfn = first_deferred_pfn, epfn = SECTION_ALIGN_UP(spfn + 1);
+ nr_pages < nr_pages_needed && spfn < zone_end_pfn(zone);
+ spfn = epfn, epfn += PAGES_PER_SECTION) {
+ nr_pages += deferred_init_memmap_chunk(spfn, epfn, zone);
}
/*
- * Initialize and free pages in MAX_PAGE_ORDER sized increments so
- * that we can avoid introducing any issues with the buddy
- * allocator.
+ * There were no pages to initialize and free which means the zone's
+ * memory map is completely initialized.
*/
- while (spfn < epfn) {
- /* update our first deferred PFN for this section */
- first_deferred_pfn = spfn;
-
- nr_pages += deferred_init_maxorder(&i, zone, &spfn, &epfn);
- touch_nmi_watchdog();
-
- /* We should only stop along section boundaries */
- if ((first_deferred_pfn ^ spfn) < PAGES_PER_SECTION)
- continue;
-
- /* If our quota has been met we can stop here */
- if (nr_pages >= nr_pages_needed)
- break;
- }
+ pgdat->first_deferred_pfn = nr_pages ? spfn : ULONG_MAX;
- pgdat->first_deferred_pfn = spfn;
pgdat_resize_unlock(pgdat, &flags);
return nr_pages > 0;
--
2.50.1
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