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Message-Id: <20220520025538.21144-3-songmuchun@bytedance.com>
Date: Fri, 20 May 2022 10:55:38 +0800
From: Muchun Song <songmuchun@...edance.com>
To: corbet@....net, akpm@...ux-foundation.org, paulmck@...nel.org,
mike.kravetz@...cle.com, osalvador@...e.de, david@...hat.com
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 v2 2/2] mm: memory_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 +++++++++----------
Documentation/admin-guide/sysctl/vm.rst | 5 ++---
include/linux/memory_hotplug.h | 9 --------
include/linux/mmzone.h | 17 +++++++++++++++
mm/hugetlb_vmemmap.c | 28 ++++++++++++++++++-------
mm/memory_hotplug.c | 22 +++++++------------
mm/sparse.c | 8 +++++++
7 files changed, 66 insertions(+), 45 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index c087f578d9d8..5359ffb04a84 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1730,9 +1730,11 @@
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.
@@ -3077,10 +3079,12 @@
[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
@@ -3090,10 +3094,6 @@
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/Documentation/admin-guide/sysctl/vm.rst b/Documentation/admin-guide/sysctl/vm.rst
index 5c9aa171a0d3..d7374a1e8ac9 100644
--- a/Documentation/admin-guide/sysctl/vm.rst
+++ b/Documentation/admin-guide/sysctl/vm.rst
@@ -565,9 +565,8 @@ See Documentation/admin-guide/mm/hugetlbpage.rst
hugetlb_optimize_vmemmap
========================
-This knob is not available when memory_hotplug.memmap_on_memory (kernel parameter)
-is configured or the size of 'struct page' (a structure defined in
-include/linux/mm_types.h) is not power of two (an unusual system config could
+This knob is not available when the size of 'struct page' (a structure defined
+in include/linux/mm_types.h) is not power of two (an unusual system config could
result in this).
Enable (set to 1) or disable (set to 0) the feature of optimizing vmemmap pages
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 20d7edf62a6a..e0b2209ab71c 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -351,13 +351,4 @@ void arch_remove_linear_mapping(u64 start, u64 size);
extern bool mhp_supports_memmap_on_memory(unsigned long size);
#endif /* CONFIG_MEMORY_HOTPLUG */
-#ifdef CONFIG_MHP_MEMMAP_ON_MEMORY
-bool mhp_memmap_on_memory(void);
-#else
-static inline bool mhp_memmap_on_memory(void)
-{
- return false;
-}
-#endif
-
#endif /* __LINUX_MEMORY_HOTPLUG_H */
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 2cf2a76535ab..607a4fcabbd4 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1434,6 +1434,7 @@ 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)
@@ -1471,6 +1472,22 @@ 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 fcd9f7872064..f12170520337 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -97,18 +97,32 @@ 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);
+
+ if (READ_ONCE(vmemmap_optimize_mode) == VMEMMAP_OPTIMIZE_OFF)
+ return 0;
+
+ 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;
- if (READ_ONCE(vmemmap_optimize_mode) == VMEMMAP_OPTIMIZE_OFF)
- return;
-
static_branch_inc(&hugetlb_optimize_vmemmap_key);
vmemmap_addr += RESERVE_VMEMMAP_SIZE;
@@ -199,10 +213,10 @@ static struct ctl_table hugetlb_vmemmap_sysctls[] = {
static __init int hugetlb_vmemmap_sysctls_init(void)
{
/*
- * If "memory_hotplug.memmap_on_memory" is enabled or "struct page"
- * crosses page boundaries, the vmemmap pages cannot be optimized.
+ * If "struct page" crosses page boundaries, the vmemmap pages cannot
+ * be optimized.
*/
- if (!mhp_memmap_on_memory() && is_power_of_2(sizeof(struct page)))
+ if (is_power_of_2(sizeof(struct page)))
register_sysctl_init("vm", hugetlb_vmemmap_sysctls);
return 0;
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 3b360eda933f..7309694c4dee 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -43,30 +43,22 @@
#include "shuffle.h"
#ifdef CONFIG_MHP_MEMMAP_ON_MEMORY
-static int memmap_on_memory_set(const char *val, const struct kernel_param *kp)
-{
- if (hugetlb_optimize_vmemmap_enabled())
- return 0;
- return param_set_bool(val, kp);
-}
-
-static const struct kernel_param_ops memmap_on_memory_ops = {
- .flags = KERNEL_PARAM_OPS_FL_NOARG,
- .set = memmap_on_memory_set,
- .get = param_get_bool,
-};
-
/*
* memory_hotplug.memmap_on_memory parameter
*/
static bool memmap_on_memory __ro_after_init;
-module_param_cb(memmap_on_memory, &memmap_on_memory_ops, &memmap_on_memory, 0444);
+module_param(memmap_on_memory, bool, 0444);
MODULE_PARM_DESC(memmap_on_memory, "Enable memmap on memory for memory hotplug");
-bool mhp_memmap_on_memory(void)
+static inline bool mhp_memmap_on_memory(void)
{
return memmap_on_memory;
}
+#else
+static inline bool mhp_memmap_on_memory(void)
+{
+ return false;
+}
#endif
enum {
diff --git a/mm/sparse.c b/mm/sparse.c
index cb3bfae64036..1f353bf9ea6b 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -913,6 +913,14 @@ 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 since the early section's
+ * vmemmap pages do not consider partially being populated.
+ */
+ 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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