* [PATCH v3 1/2] mm: memory_hotplug: enumerate all supported section flags
2022-06-17 13:56 [PATCH v3 0/2] make hugetlb_optimize_vmemmap compatible with memmap_on_memory Muchun Song
@ 2022-06-17 13:56 ` Muchun Song
2022-06-17 13:56 ` [PATCH v3 2/2] mm: memory_hotplug: make hugetlb_optimize_vmemmap compatible with memmap_on_memory Muchun Song
1 sibling, 0 replies; 3+ messages in thread
From: Muchun Song @ 2022-06-17 13:56 UTC (permalink / raw)
To: akpm, corbet, david, mike.kravetz, osalvador, paulmck
Cc: linux-doc, linux-kernel, linux-mm, duanxiongchun, smuchun, Muchun Song
We are almost running out of section flags, only one bit is available in
the worst case (powerpc with 256k pages). However, there are still some
free bits (in ->section_mem_map) on other architectures (e.g. x86_64 has
10 bits available, arm64 has 8 bits available with worst case of 64K
pages). We have hard coded those numbers in code, it is inconvenient to
use those bits on other architectures except powerpc. So transfer those
section flags to enumeration to make it easy to add new section flags in
the future. Also, move SECTION_TAINT_ZONE_DEVICE into the scope of
CONFIG_ZONE_DEVICE to save a bit on non-zone-device case.
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
include/linux/mmzone.h | 44 +++++++++++++++++++++++++++++++++++---------
mm/memory_hotplug.c | 6 ++++++
mm/sparse.c | 2 +-
3 files changed, 42 insertions(+), 10 deletions(-)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index aab70355d64f..932843c6459b 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1418,16 +1418,35 @@ extern size_t mem_section_usage_size(void);
* (equal SECTION_SIZE_BITS - PAGE_SHIFT), and the
* worst combination is powerpc with 256k pages,
* which results in PFN_SECTION_SHIFT equal 6.
- * To sum it up, at least 6 bits are available.
+ * To sum it up, at least 6 bits are available on all architectures.
+ * However, we can exceed 6 bits on some other architectures except
+ * powerpc (e.g. 15 bits are available on x86_64, 13 bits are available
+ * with the worst case of 64K pages on arm64) if we make sure the
+ * exceeded bit is not applicable to powerpc.
*/
-#define SECTION_MARKED_PRESENT (1UL<<0)
-#define SECTION_HAS_MEM_MAP (1UL<<1)
-#define SECTION_IS_ONLINE (1UL<<2)
-#define SECTION_IS_EARLY (1UL<<3)
-#define SECTION_TAINT_ZONE_DEVICE (1UL<<4)
-#define SECTION_MAP_LAST_BIT (1UL<<5)
-#define SECTION_MAP_MASK (~(SECTION_MAP_LAST_BIT-1))
-#define SECTION_NID_SHIFT 6
+enum {
+ SECTION_MARKED_PRESENT_BIT,
+ SECTION_HAS_MEM_MAP_BIT,
+ SECTION_IS_ONLINE_BIT,
+ SECTION_IS_EARLY_BIT,
+#ifdef CONFIG_ZONE_DEVICE
+ SECTION_TAINT_ZONE_DEVICE_BIT,
+#endif
+ SECTION_MAP_LAST_BIT,
+};
+
+enum {
+ SECTION_MARKED_PRESENT = BIT(SECTION_MARKED_PRESENT_BIT),
+ SECTION_HAS_MEM_MAP = BIT(SECTION_HAS_MEM_MAP_BIT),
+ SECTION_IS_ONLINE = BIT(SECTION_IS_ONLINE_BIT),
+ SECTION_IS_EARLY = BIT(SECTION_IS_EARLY_BIT),
+#ifdef CONFIG_ZONE_DEVICE
+ SECTION_TAINT_ZONE_DEVICE = BIT(SECTION_TAINT_ZONE_DEVICE_BIT),
+#endif
+};
+
+#define SECTION_MAP_MASK (~(BIT(SECTION_MAP_LAST_BIT) - 1))
+#define SECTION_NID_SHIFT SECTION_MAP_LAST_BIT
static inline struct page *__section_mem_map_addr(struct mem_section *section)
{
@@ -1466,12 +1485,19 @@ static inline int online_section(struct mem_section *section)
return (section && (section->section_mem_map & SECTION_IS_ONLINE));
}
+#ifdef CONFIG_ZONE_DEVICE
static inline int online_device_section(struct mem_section *section)
{
unsigned long flags = SECTION_IS_ONLINE | SECTION_TAINT_ZONE_DEVICE;
return section && ((section->section_mem_map & flags) == flags);
}
+#else
+static inline int online_device_section(struct mem_section *section)
+{
+ return 0;
+}
+#endif
static inline int online_section_nr(unsigned long nr)
{
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 1f1a730c4499..6662b86e9e64 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -670,12 +670,18 @@ static void __meminit resize_pgdat_range(struct pglist_data *pgdat, unsigned lon
}
+#ifdef CONFIG_ZONE_DEVICE
static void section_taint_zone_device(unsigned long pfn)
{
struct mem_section *ms = __pfn_to_section(pfn);
ms->section_mem_map |= SECTION_TAINT_ZONE_DEVICE;
}
+#else
+static inline void section_taint_zone_device(unsigned long pfn)
+{
+}
+#endif
/*
* Associate the pfn range with the given zone, initializing the memmaps
diff --git a/mm/sparse.c b/mm/sparse.c
index cb3bfae64036..e5a8a3a0edd7 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -281,7 +281,7 @@ static unsigned long sparse_encode_mem_map(struct page *mem_map, unsigned long p
{
unsigned long coded_mem_map =
(unsigned long)(mem_map - (section_nr_to_pfn(pnum)));
- BUILD_BUG_ON(SECTION_MAP_LAST_BIT > (1UL<<PFN_SECTION_SHIFT));
+ BUILD_BUG_ON(SECTION_MAP_LAST_BIT > PFN_SECTION_SHIFT);
BUG_ON(coded_mem_map & ~SECTION_MAP_MASK);
return coded_mem_map;
}
--
2.11.0
^ permalink raw reply [flat|nested] 3+ messages in thread* [PATCH v3 2/2] mm: memory_hotplug: make hugetlb_optimize_vmemmap compatible with memmap_on_memory
2022-06-17 13:56 [PATCH v3 0/2] make hugetlb_optimize_vmemmap compatible with memmap_on_memory Muchun Song
2022-06-17 13:56 ` [PATCH v3 1/2] mm: memory_hotplug: enumerate all supported section flags Muchun Song
@ 2022-06-17 13:56 ` Muchun Song
1 sibling, 0 replies; 3+ messages in thread
From: Muchun Song @ 2022-06-17 13:56 UTC (permalink / raw)
To: akpm, corbet, david, mike.kravetz, osalvador, paulmck
Cc: linux-doc, linux-kernel, linux-mm, duanxiongchun, smuchun, Muchun Song
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 VmemmapSelfHosted to mask any
non-optimizable vmemmap pages. The hugetlb_vmemmap can use this flag
to detect if a vmemmap page can be optimized.
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Co-developed-by: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Oscar Salvador <osalvador@suse.de>
---
Documentation/admin-guide/kernel-parameters.txt | 22 ++++++------
Documentation/admin-guide/sysctl/vm.rst | 5 ++-
include/linux/memory_hotplug.h | 9 -----
include/linux/page-flags.h | 11 ++++++
mm/hugetlb_vmemmap.c | 47 ++++++++++++++++++++-----
mm/memory_hotplug.c | 27 ++++++--------
6 files changed, 74 insertions(+), 47 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 8090130b544b..d740e2ed0e61 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1722,9 +1722,11 @@
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.
@@ -3069,10 +3071,12 @@
[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
@@ -3082,10 +3086,6 @@
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/page-flags.h b/include/linux/page-flags.h
index e66f7aa3191d..2aa5dcbfe468 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -193,6 +193,11 @@ enum pageflags {
/* Only valid for buddy pages. Used to track pages that are reported */
PG_reported = PG_uptodate,
+
+#ifdef CONFIG_MEMORY_HOTPLUG
+ /* For self-hosted memmap pages */
+ PG_vmemmap_self_hosted = PG_owner_priv_1,
+#endif
};
#define PAGEFLAGS_MASK ((1UL << NR_PAGEFLAGS) - 1)
@@ -628,6 +633,12 @@ PAGEFLAG_FALSE(SkipKASanPoison, skip_kasan_poison)
*/
__PAGEFLAG(Reported, reported, PF_NO_COMPOUND)
+#ifdef CONFIG_MEMORY_HOTPLUG
+PAGEFLAG(VmemmapSelfHosted, vmemmap_self_hosted, PF_ANY)
+#else
+PAGEFLAG_FALSE(VmemmapSelfHosted, vmemmap_self_hosted)
+#endif
+
/*
* On an anonymous page mapped into a user virtual memory area,
* page->mapping points to its anon_vma, not to a struct address_space;
diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
index 1089ea8a9c98..982f27c24a95 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -10,7 +10,6 @@
*/
#define pr_fmt(fmt) "HugeTLB: " fmt
-#include <linux/memory_hotplug.h>
#include "hugetlb_vmemmap.h"
/*
@@ -97,18 +96,50 @@ int hugetlb_vmemmap_alloc(struct hstate *h, struct page *head)
return ret;
}
+static unsigned int vmemmap_optimizable_pages(struct hstate *h,
+ struct page *head)
+{
+ struct mem_section *ms;
+ struct page *vmemmap_page;
+ unsigned long pfn = page_to_pfn(head);
+
+ if (READ_ONCE(vmemmap_optimize_mode) == VMEMMAP_OPTIMIZE_OFF)
+ return 0;
+
+ ms = __pfn_to_section(pfn);
+ vmemmap_page = sparse_decode_mem_map(ms->section_mem_map,
+ pfn_to_section_nr(pfn));
+ /*
+ * Only the vmemmap pages' vmemmap may be marked as VmemmapSelfHosted.
+ *
+ * Due to HugeTLB alignment requirements, and the vmemmap pages being
+ * at the start of the hotplugged memory region. Checking any vmemmap
+ * page's vmemmap is fine.
+ *
+ * [ hotplugged memory ]
+ * [ vmemmap ][ usable memory ]
+ * ^ | | |
+ * +---+ | |
+ * ^ | |
+ * +--------+ |
+ * ^ |
+ * +-----------------+
+ */
+ if (PageVmemmapSelfHosted(vmemmap_page))
+ 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 = vmemmap_optimizable_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 +230,10 @@ 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 6662b86e9e64..3a59d4e97c03 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 {
@@ -1035,7 +1027,7 @@ int mhp_init_memmap_on_memory(unsigned long pfn, unsigned long nr_pages,
struct zone *zone)
{
unsigned long end_pfn = pfn + nr_pages;
- int ret;
+ int ret, i;
ret = kasan_add_zero_shadow(__va(PFN_PHYS(pfn)), PFN_PHYS(nr_pages));
if (ret)
@@ -1043,6 +1035,9 @@ int mhp_init_memmap_on_memory(unsigned long pfn, unsigned long nr_pages,
move_pfn_range_to_zone(zone, pfn, nr_pages, NULL, MIGRATE_UNMOVABLE);
+ for (i = 0; i < nr_pages; i++)
+ SetPageVmemmapSelfHosted(pfn_to_page(pfn + i));
+
/*
* It might be that the vmemmap_pages fully span sections. If that is
* the case, mark those sections online here as otherwise they will be
--
2.11.0
^ permalink raw reply [flat|nested] 3+ messages in thread