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Date: Mon, 16 May 2022 18:22:08 +0800
From: Muchun Song <songmuchun@...edance.com>
To: corbet@....net, mike.kravetz@...cle.com, akpm@...ux-foundation.org,
mcgrof@...nel.org, keescook@...omium.org, yzaikin@...gle.com,
osalvador@...e.de, david@...hat.com, masahiroy@...nel.org
Cc: linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, duanxiongchun@...edance.com, smuchun@...il.com,
Muchun Song <songmuchun@...edance.com>
Subject: [PATCH v12 4/7] mm: hotplug: introduce SECTION_CANNOT_OPTIMIZE_VMEMMAP
For now, the feature of hugetlb_free_vmemmap is not compatible with the
feature of memory_hotplug.memmap_on_memory, and hugetlb_free_vmemmap
takes precedence over memory_hotplug.memmap_on_memory. However, someone
wants to make memory_hotplug.memmap_on_memory takes precedence over
hugetlb_free_vmemmap since memmap_on_memory makes it more likely to
succeed memory hotplug in close-to-OOM situations. So the decision
of making hugetlb_free_vmemmap take precedence is not wise and elegant.
The proper approach is to have hugetlb_vmemmap.c do the check whether
the section which the HugeTLB pages belong to can be optimized. If
the section's vmemmap pages are allocated from the added memory block
itself, hugetlb_free_vmemmap should refuse to optimize the vmemmap,
otherwise, do the optimization. Then both kernel parameters are
compatible. So this patch introduces SECTION_CANNOT_OPTIMIZE_VMEMMAP
to indicate whether the section could be optimized.
Signed-off-by: Muchun Song <songmuchun@...edance.com>
---
Documentation/admin-guide/kernel-parameters.txt | 22 +++++++++++-----------
include/linux/mmzone.h | 17 +++++++++++++++++
mm/hugetlb_vmemmap.c | 16 +++++++++++++++-
mm/memory_hotplug.c | 1 -
mm/sparse.c | 7 +++++++
5 files changed, 50 insertions(+), 13 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 308da668bbb1..a0a014f2104c 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1711,9 +1711,11 @@
Built with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y,
the default is on.
- This is not compatible with memory_hotplug.memmap_on_memory.
- If both parameters are enabled, hugetlb_free_vmemmap takes
- precedence over memory_hotplug.memmap_on_memory.
+ Note that the vmemmap pages may be allocated from the added
+ memory block itself when memory_hotplug.memmap_on_memory is
+ enabled, those vmemmap pages cannot be optimized even if this
+ feature is enabled. Other vmemmap pages not allocated from
+ the added memory block itself do not be affected.
hung_task_panic=
[KNL] Should the hung task detector generate panics.
@@ -3038,10 +3040,12 @@
[KNL,X86,ARM] Boolean flag to enable this feature.
Format: {on | off (default)}
When enabled, runtime hotplugged memory will
- allocate its internal metadata (struct pages)
- from the hotadded memory which will allow to
- hotadd a lot of memory without requiring
- additional memory to do so.
+ allocate its internal metadata (struct pages,
+ those vmemmap pages cannot be optimized even
+ if hugetlb_free_vmemmap is enabled) from the
+ hotadded memory which will allow to hotadd a
+ lot of memory without requiring additional
+ memory to do so.
This feature is disabled by default because it
has some implication on large (e.g. GB)
allocations in some configurations (e.g. small
@@ -3051,10 +3055,6 @@
Note that even when enabled, there are a few cases where
the feature is not effective.
- This is not compatible with hugetlb_free_vmemmap. If
- both parameters are enabled, hugetlb_free_vmemmap takes
- precedence over memory_hotplug.memmap_on_memory.
-
memtest= [KNL,X86,ARM,M68K,PPC,RISCV] Enable memtest
Format: <integer>
default : 0 <disable>
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index af057e20b9d7..7b69acc5c2a9 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1430,6 +1430,7 @@ extern size_t mem_section_usage_size(void);
MAPPER(IS_ONLINE) \
MAPPER(IS_EARLY) \
MAPPER(TAINT_ZONE_DEVICE, CONFIG_ZONE_DEVICE) \
+ MAPPER(CANNOT_OPTIMIZE_VMEMMAP, CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP) \
MAPPER(MAP_LAST_BIT)
#define __SECTION_SHIFT_FLAG_MAPPER_0(x)
@@ -1457,6 +1458,22 @@ static inline struct page *__section_mem_map_addr(struct mem_section *section)
return (struct page *)map;
}
+#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
+static inline void section_mark_cannot_optimize_vmemmap(struct mem_section *ms)
+{
+ ms->section_mem_map |= SECTION_CANNOT_OPTIMIZE_VMEMMAP;
+}
+
+static inline int section_cannot_optimize_vmemmap(struct mem_section *ms)
+{
+ return (ms && (ms->section_mem_map & SECTION_CANNOT_OPTIMIZE_VMEMMAP));
+}
+#else
+static inline void section_mark_cannot_optimize_vmemmap(struct mem_section *ms)
+{
+}
+#endif
+
static inline int present_section(struct mem_section *section)
{
return (section && (section->section_mem_map & SECTION_MARKED_PRESENT));
diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
index cc4ec752ec16..970c36b8935f 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -75,12 +75,26 @@ int hugetlb_vmemmap_alloc(struct hstate *h, struct page *head)
return ret;
}
+static unsigned int optimizable_vmemmap_pages(struct hstate *h,
+ struct page *head)
+{
+ unsigned long pfn = page_to_pfn(head);
+ unsigned long end = pfn + pages_per_huge_page(h);
+
+ for (; pfn < end; pfn += PAGES_PER_SECTION) {
+ if (section_cannot_optimize_vmemmap(__pfn_to_section(pfn)))
+ return 0;
+ }
+
+ return hugetlb_optimize_vmemmap_pages(h);
+}
+
void hugetlb_vmemmap_free(struct hstate *h, struct page *head)
{
unsigned long vmemmap_addr = (unsigned long)head;
unsigned long vmemmap_end, vmemmap_reuse, vmemmap_pages;
- vmemmap_pages = hugetlb_optimize_vmemmap_pages(h);
+ vmemmap_pages = optimizable_vmemmap_pages(h, head);
if (!vmemmap_pages)
return;
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index aef3f041dec7..1d0225d57166 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1270,7 +1270,6 @@ bool mhp_supports_memmap_on_memory(unsigned long size)
* populate a single PMD.
*/
return memmap_on_memory &&
- !hugetlb_optimize_vmemmap_enabled() &&
IS_ENABLED(CONFIG_MHP_MEMMAP_ON_MEMORY) &&
size == memory_block_size_bytes() &&
IS_ALIGNED(vmemmap_size, PMD_SIZE) &&
diff --git a/mm/sparse.c b/mm/sparse.c
index d2d76d158b39..8197ef9b7c4c 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -913,6 +913,13 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn,
ms = __nr_to_section(section_nr);
set_section_nid(section_nr, nid);
__section_mark_present(ms, section_nr);
+ /*
+ * Mark whole section as non-optimizable once there is a subsection
+ * whose vmemmap pages are allocated from alternative allocator. The
+ * early section is always optimizable.
+ */
+ if (!early_section(ms) && altmap)
+ section_mark_cannot_optimize_vmemmap(ms);
/* Align memmap to section boundary in the subsection case */
if (section_nr_to_pfn(section_nr) != start_pfn)
--
2.11.0
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