mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-09-04 18:09:57 +00:00
![Oscar Salvador](/assets/img/avatar_default.png)
Physical memory hotadd has to allocate a memmap (struct page array) for the newly added memory section. Currently, alloc_pages_node() is used for those allocations. This has some disadvantages: a) an existing memory is consumed for that purpose (eg: ~2MB per 128MB memory section on x86_64) This can even lead to extreme cases where system goes OOM because the physically hotplugged memory depletes the available memory before it is onlined. b) if the whole node is movable then we have off-node struct pages which has performance drawbacks. c) It might be there are no PMD_ALIGNED chunks so memmap array gets populated with base pages. This can be improved when CONFIG_SPARSEMEM_VMEMMAP is enabled. Vmemap page tables can map arbitrary memory. That means that we can reserve a part of the physically hotadded memory to back vmemmap page tables. This implementation uses the beginning of the hotplugged memory for that purpose. There are some non-obviously things to consider though. Vmemmap pages are allocated/freed during the memory hotplug events (add_memory_resource(), try_remove_memory()) when the memory is added/removed. This means that the reserved physical range is not online although it is used. The most obvious side effect is that pfn_to_online_page() returns NULL for those pfns. The current design expects that this should be OK as the hotplugged memory is considered a garbage until it is onlined. For example hibernation wouldn't save the content of those vmmemmaps into the image so it wouldn't be restored on resume but this should be OK as there no real content to recover anyway while metadata is reachable from other data structures (e.g. vmemmap page tables). The reserved space is therefore (de)initialized during the {on,off}line events (mhp_{de}init_memmap_on_memory). That is done by extracting page allocator independent initialization from the regular onlining path. The primary reason to handle the reserved space outside of {on,off}line_pages is to make each initialization specific to the purpose rather than special case them in a single function. As per above, the functions that are introduced are: - mhp_init_memmap_on_memory: Initializes vmemmap pages by calling move_pfn_range_to_zone(), calls kasan_add_zero_shadow(), and onlines as many sections as vmemmap pages fully span. - mhp_deinit_memmap_on_memory: Offlines as many sections as vmemmap pages fully span, removes the range from zhe zone by remove_pfn_range_from_zone(), and calls kasan_remove_zero_shadow() for the range. The new function memory_block_online() calls mhp_init_memmap_on_memory() before doing the actual online_pages(). Should online_pages() fail, we clean up by calling mhp_deinit_memmap_on_memory(). Adjusting of present_pages is done at the end once we know that online_pages() succedeed. On offline, memory_block_offline() needs to unaccount vmemmap pages from present_pages() before calling offline_pages(). This is necessary because offline_pages() tears down some structures based on the fact whether the node or the zone become empty. If offline_pages() fails, we account back vmemmap pages. If it succeeds, we call mhp_deinit_memmap_on_memory(). Hot-remove: We need to be careful when removing memory, as adding and removing memory needs to be done with the same granularity. To check that this assumption is not violated, we check the memory range we want to remove and if a) any memory block has vmemmap pages and b) the range spans more than a single memory block, we scream out loud and refuse to proceed. If all is good and the range was using memmap on memory (aka vmemmap pages), we construct an altmap structure so free_hugepage_table does the right thing and calls vmem_altmap_free instead of free_pagetable. Link: https://lkml.kernel.org/r/20210421102701.25051-5-osalvador@suse.de Signed-off-by: Oscar Salvador <osalvador@suse.de> Reviewed-by: David Hildenbrand <david@redhat.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Anshuman Khandual <anshuman.khandual@arm.com> Cc: Pavel Tatashin <pasha.tatashin@soleen.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
122 lines
3.8 KiB
C
122 lines
3.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
/*
|
|
* include/linux/memory.h - generic memory definition
|
|
*
|
|
* This is mainly for topological representation. We define the
|
|
* basic "struct memory_block" here, which can be embedded in per-arch
|
|
* definitions or NUMA information.
|
|
*
|
|
* Basic handling of the devices is done in drivers/base/memory.c
|
|
* and system devices are handled in drivers/base/sys.c.
|
|
*
|
|
* Memory block are exported via sysfs in the class/memory/devices/
|
|
* directory.
|
|
*
|
|
*/
|
|
#ifndef _LINUX_MEMORY_H_
|
|
#define _LINUX_MEMORY_H_
|
|
|
|
#include <linux/node.h>
|
|
#include <linux/compiler.h>
|
|
#include <linux/mutex.h>
|
|
#include <linux/notifier.h>
|
|
|
|
#define MIN_MEMORY_BLOCK_SIZE (1UL << SECTION_SIZE_BITS)
|
|
|
|
struct memory_block {
|
|
unsigned long start_section_nr;
|
|
unsigned long state; /* serialized by the dev->lock */
|
|
int online_type; /* for passing data to online routine */
|
|
int nid; /* NID for this memory block */
|
|
struct device dev;
|
|
/*
|
|
* Number of vmemmap pages. These pages
|
|
* lay at the beginning of the memory block.
|
|
*/
|
|
unsigned long nr_vmemmap_pages;
|
|
};
|
|
|
|
int arch_get_memory_phys_device(unsigned long start_pfn);
|
|
unsigned long memory_block_size_bytes(void);
|
|
int set_memory_block_size_order(unsigned int order);
|
|
|
|
/* These states are exposed to userspace as text strings in sysfs */
|
|
#define MEM_ONLINE (1<<0) /* exposed to userspace */
|
|
#define MEM_GOING_OFFLINE (1<<1) /* exposed to userspace */
|
|
#define MEM_OFFLINE (1<<2) /* exposed to userspace */
|
|
#define MEM_GOING_ONLINE (1<<3)
|
|
#define MEM_CANCEL_ONLINE (1<<4)
|
|
#define MEM_CANCEL_OFFLINE (1<<5)
|
|
|
|
struct memory_notify {
|
|
unsigned long start_pfn;
|
|
unsigned long nr_pages;
|
|
int status_change_nid_normal;
|
|
int status_change_nid_high;
|
|
int status_change_nid;
|
|
};
|
|
|
|
struct notifier_block;
|
|
struct mem_section;
|
|
|
|
/*
|
|
* Priorities for the hotplug memory callback routines (stored in decreasing
|
|
* order in the callback chain)
|
|
*/
|
|
#define SLAB_CALLBACK_PRI 1
|
|
#define IPC_CALLBACK_PRI 10
|
|
|
|
#ifndef CONFIG_MEMORY_HOTPLUG_SPARSE
|
|
static inline void memory_dev_init(void)
|
|
{
|
|
return;
|
|
}
|
|
static inline int register_memory_notifier(struct notifier_block *nb)
|
|
{
|
|
return 0;
|
|
}
|
|
static inline void unregister_memory_notifier(struct notifier_block *nb)
|
|
{
|
|
}
|
|
static inline int memory_notify(unsigned long val, void *v)
|
|
{
|
|
return 0;
|
|
}
|
|
#else
|
|
extern int register_memory_notifier(struct notifier_block *nb);
|
|
extern void unregister_memory_notifier(struct notifier_block *nb);
|
|
int create_memory_block_devices(unsigned long start, unsigned long size,
|
|
unsigned long vmemmap_pages);
|
|
void remove_memory_block_devices(unsigned long start, unsigned long size);
|
|
extern void memory_dev_init(void);
|
|
extern int memory_notify(unsigned long val, void *v);
|
|
extern struct memory_block *find_memory_block(struct mem_section *);
|
|
typedef int (*walk_memory_blocks_func_t)(struct memory_block *, void *);
|
|
extern int walk_memory_blocks(unsigned long start, unsigned long size,
|
|
void *arg, walk_memory_blocks_func_t func);
|
|
extern int for_each_memory_block(void *arg, walk_memory_blocks_func_t func);
|
|
#define CONFIG_MEM_BLOCK_SIZE (PAGES_PER_SECTION<<PAGE_SHIFT)
|
|
#endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */
|
|
|
|
#ifdef CONFIG_MEMORY_HOTPLUG
|
|
#define hotplug_memory_notifier(fn, pri) ({ \
|
|
static __meminitdata struct notifier_block fn##_mem_nb =\
|
|
{ .notifier_call = fn, .priority = pri };\
|
|
register_memory_notifier(&fn##_mem_nb); \
|
|
})
|
|
#define register_hotmemory_notifier(nb) register_memory_notifier(nb)
|
|
#define unregister_hotmemory_notifier(nb) unregister_memory_notifier(nb)
|
|
#else
|
|
#define hotplug_memory_notifier(fn, pri) ({ 0; })
|
|
/* These aren't inline functions due to a GCC bug. */
|
|
#define register_hotmemory_notifier(nb) ({ (void)(nb); 0; })
|
|
#define unregister_hotmemory_notifier(nb) ({ (void)(nb); })
|
|
#endif
|
|
|
|
/*
|
|
* Kernel text modification mutex, used for code patching. Users of this lock
|
|
* can sleep.
|
|
*/
|
|
extern struct mutex text_mutex;
|
|
|
|
#endif /* _LINUX_MEMORY_H_ */
|