| Message ID | 20230823131350.114942-5-alexandru.elisei@arm.com (mailing list archive) |
|---|---|
| State | Handled Elsewhere |
| Headers | show |
| Series | [RFC,01/37] mm: page_alloc: Rename gfp_to_alloc_flags_cma -> gfp_to_alloc_flags_fast | expand |
On Wed, Aug 23, 2023 at 02:13:17PM +0100, Alexandru Elisei wrote: > Some architectures implement hardware memory coloring to catch incorrect > usage of memory allocation. One such architecture is arm64, which calls its > hardware implementation Memory Tagging Extension. > > So far, the memory which stores the metadata has been configured by > firmware and hidden from Linux. For arm64, it is impossible to to have the > entire system RAM allocated with metadata because executable memory cannot > be tagged. Furthermore, in practice, only a chunk of all the memory that > can have tags is actually used as tagged. which leaves a portion of > metadata memory unused. As such, it would be beneficial to use this memory, > which so far has been unaccessible to Linux, to service allocation > requests. To prepare for exposing this metadata memory a new migratetype is > being added to the page allocator, called MIGRATE_METADATA. > > One important aspect is that for arm64 the memory that stores metadata > cannot have metadata associated with it, it can only be used to store > metadata for other pages. This means that the page allocator will *not* > allocate from this migratetype if at least one of the following is true: > > - The allocation also needs metadata to be allocated. > - The allocation isn't movable. A metadata page storing data must be > able to be migrated at any given time so it can be repurposed to store > metadata. > > Both cases are specific to arm64's implementation of memory metadata. > > For now, metadata storage pages management is disabled, and it will be > enabled once the architecture-specific handling is added. > > Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com> > --- > arch/arm64/include/asm/memory_metadata.h | 21 ++++++++++++++++++ > arch/arm64/mm/fault.c | 3 +++ > include/asm-generic/Kbuild | 1 + > include/asm-generic/memory_metadata.h | 18 +++++++++++++++ > include/linux/mmzone.h | 11 ++++++++++ > mm/Kconfig | 3 +++ > mm/internal.h | 5 +++++ > mm/page_alloc.c | 28 ++++++++++++++++++++++++ > 8 files changed, 90 insertions(+) > create mode 100644 arch/arm64/include/asm/memory_metadata.h > create mode 100644 include/asm-generic/memory_metadata.h > > diff --git a/arch/arm64/include/asm/memory_metadata.h b/arch/arm64/include/asm/memory_metadata.h > new file mode 100644 > index 000000000000..5269be7f455f > --- /dev/null > +++ b/arch/arm64/include/asm/memory_metadata.h > @@ -0,0 +1,21 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +/* > + * Copyright (C) 2023 ARM Ltd. > + */ > +#ifndef __ASM_MEMORY_METADATA_H > +#define __ASM_MEMORY_METADATA_H > + > +#include <asm-generic/memory_metadata.h> > + > +#ifdef CONFIG_MEMORY_METADATA > +static inline bool metadata_storage_enabled(void) > +{ > + return false; > +} > +static inline bool alloc_can_use_metadata_pages(gfp_t gfp_mask) > +{ > + return false; > +} > +#endif /* CONFIG_MEMORY_METADATA */ > + > +#endif /* __ASM_MEMORY_METADATA_H */ > diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c > index 0ca89ebcdc63..1ca421c11ebc 100644 > --- a/arch/arm64/mm/fault.c > +++ b/arch/arm64/mm/fault.c > @@ -13,6 +13,7 @@ > #include <linux/kfence.h> > #include <linux/signal.h> > #include <linux/mm.h> > +#include <linux/mmzone.h> > #include <linux/hardirq.h> > #include <linux/init.h> > #include <linux/kasan.h> > @@ -956,6 +957,8 @@ struct folio *vma_alloc_zeroed_movable_folio(struct vm_area_struct *vma, > > void tag_clear_highpage(struct page *page) > { > + /* Tag storage pages cannot be tagged. */ > + WARN_ON_ONCE(is_migrate_metadata_page(page)); > /* Newly allocated page, shouldn't have been tagged yet */ > WARN_ON_ONCE(!try_page_mte_tagging(page)); > mte_zero_clear_page_tags(page_address(page)); > diff --git a/include/asm-generic/Kbuild b/include/asm-generic/Kbuild > index 941be574bbe0..048ecffc430c 100644 > --- a/include/asm-generic/Kbuild > +++ b/include/asm-generic/Kbuild > @@ -36,6 +36,7 @@ mandatory-y += kprobes.h > mandatory-y += linkage.h > mandatory-y += local.h > mandatory-y += local64.h > +mandatory-y += memory_metadata.h > mandatory-y += mmiowb.h > mandatory-y += mmu.h > mandatory-y += mmu_context.h > diff --git a/include/asm-generic/memory_metadata.h b/include/asm-generic/memory_metadata.h > new file mode 100644 > index 000000000000..dc0c84408a8e > --- /dev/null > +++ b/include/asm-generic/memory_metadata.h > @@ -0,0 +1,18 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef __ASM_GENERIC_MEMORY_METADATA_H > +#define __ASM_GENERIC_MEMORY_METADATA_H > + > +#include <linux/gfp.h> > + > +#ifndef CONFIG_MEMORY_METADATA > +static inline bool metadata_storage_enabled(void) > +{ > + return false; > +} > +static inline bool alloc_can_use_metadata_pages(gfp_t gfp_mask) > +{ > + return false; > +} > +#endif /* !CONFIG_MEMORY_METADATA */ > + > +#endif /* __ASM_GENERIC_MEMORY_METADATA_H */ > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index 5e50b78d58ea..74925806687e 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -61,6 +61,9 @@ enum migratetype { > */ > MIGRATE_CMA, > #endif > +#ifdef CONFIG_MEMORY_METADATA > + MIGRATE_METADATA, > +#endif > #ifdef CONFIG_MEMORY_ISOLATION > MIGRATE_ISOLATE, /* can't allocate from here */ > #endif > @@ -78,6 +81,14 @@ extern const char * const migratetype_names[MIGRATE_TYPES]; > # define is_migrate_cma_page(_page) false > #endif > > +#ifdef CONFIG_MEMORY_METADATA > +# define is_migrate_metadata(migratetype) unlikely((migratetype) == MIGRATE_METADATA) > +# define is_migrate_metadata_page(_page) (get_pageblock_migratetype(_page) == MIGRATE_METADATA) > +#else > +# define is_migrate_metadata(migratetype) false > +# define is_migrate_metadata_page(_page) false > +#endif > + > static inline bool is_migrate_movable(int mt) > { > return is_migrate_cma(mt) || mt == MIGRATE_MOVABLE; > diff --git a/mm/Kconfig b/mm/Kconfig > index 09130434e30d..838193522e20 100644 > --- a/mm/Kconfig > +++ b/mm/Kconfig > @@ -1236,6 +1236,9 @@ config LOCK_MM_AND_FIND_VMA > bool > depends on !STACK_GROWSUP > > +config MEMORY_METADATA > + bool > + > source "mm/damon/Kconfig" > > endmenu > diff --git a/mm/internal.h b/mm/internal.h > index a7d9e980429a..efd52c9f1578 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -824,6 +824,11 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone, > #define ALLOC_NOFRAGMENT 0x0 > #endif > #define ALLOC_HIGHATOMIC 0x200 /* Allows access to MIGRATE_HIGHATOMIC */ > +#ifdef CONFIG_MEMORY_METADATA > +#define ALLOC_FROM_METADATA 0x400 /* allow allocations from MIGRATE_METADATA list */ > +#else > +#define ALLOC_FROM_METADATA 0x0 > +#endif > #define ALLOC_KSWAPD 0x800 /* allow waking of kswapd, __GFP_KSWAPD_RECLAIM set */ > > /* Flags that allow allocations below the min watermark. */ > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index fdc230440a44..7baa78abf351 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -53,6 +53,7 @@ > #include <linux/khugepaged.h> > #include <linux/delayacct.h> > #include <asm/div64.h> > +#include <asm/memory_metadata.h> > #include "internal.h" > #include "shuffle.h" > #include "page_reporting.h" > @@ -1645,6 +1646,17 @@ static inline struct page *__rmqueue_cma_fallback(struct zone *zone, > unsigned int order) { return NULL; } > #endif > > +#ifdef CONFIG_MEMORY_METADATA > +static __always_inline struct page *__rmqueue_metadata_fallback(struct zone *zone, > + unsigned int order) > +{ > + return __rmqueue_smallest(zone, order, MIGRATE_METADATA); > +} > +#else > +static inline struct page *__rmqueue_metadata_fallback(struct zone *zone, > + unsigned int order) { return NULL; } > +#endif > + > /* > * Move the free pages in a range to the freelist tail of the requested type. > * Note that start_page and end_pages are not aligned on a pageblock > @@ -2144,6 +2156,15 @@ __rmqueue(struct zone *zone, unsigned int order, int migratetype, > if (alloc_flags & ALLOC_CMA) > page = __rmqueue_cma_fallback(zone, order); > > + /* > + * Allocate data pages from MIGRATE_METADATA only if the regular > + * allocation path fails to increase the chance that the > + * metadata page is available when the associated data page > + * needs it. > + */ > + if (!page && (alloc_flags & ALLOC_FROM_METADATA)) > + page = __rmqueue_metadata_fallback(zone, order); > + Hi! I guess it would cause non-movable page starving issue as CMA. The metadata pages cannot be used for non-movable allocations. Metadata pages are utilized poorly, non-movable allocations may end up getting starved if all regular movable pages are allocated and the only pages left are metadata. If the system has a lot of CMA pages, then this problem would become more bad. I think it would be better to make use of it in places where performance is not critical, including some GFP_METADATA ? Thanks, Hyesoo Yu. > if (!page && __rmqueue_fallback(zone, order, migratetype, > alloc_flags)) > goto retry; > @@ -3088,6 +3109,13 @@ static inline unsigned int gfp_to_alloc_flags_fast(gfp_t gfp_mask, > if (gfp_migratetype(gfp_mask) == MIGRATE_MOVABLE) > alloc_flags |= ALLOC_CMA; > #endif > +#ifdef CONFIG_MEMORY_METADATA > + if (metadata_storage_enabled() && > + gfp_migratetype(gfp_mask) == MIGRATE_MOVABLE && > + alloc_can_use_metadata_pages(gfp_mask)) > + alloc_flags |= ALLOC_FROM_METADATA; > +#endif > + > return alloc_flags; > } > > -- > 2.41.0 > >
Hello, On Thu, Oct 12, 2023 at 10:28:24AM +0900, Hyesoo Yu wrote: > On Wed, Aug 23, 2023 at 02:13:17PM +0100, Alexandru Elisei wrote: > > Some architectures implement hardware memory coloring to catch incorrect > > usage of memory allocation. One such architecture is arm64, which calls its > > hardware implementation Memory Tagging Extension. > > > > So far, the memory which stores the metadata has been configured by > > firmware and hidden from Linux. For arm64, it is impossible to to have the > > entire system RAM allocated with metadata because executable memory cannot > > be tagged. Furthermore, in practice, only a chunk of all the memory that > > can have tags is actually used as tagged. which leaves a portion of > > metadata memory unused. As such, it would be beneficial to use this memory, > > which so far has been unaccessible to Linux, to service allocation > > requests. To prepare for exposing this metadata memory a new migratetype is > > being added to the page allocator, called MIGRATE_METADATA. > > > > One important aspect is that for arm64 the memory that stores metadata > > cannot have metadata associated with it, it can only be used to store > > metadata for other pages. This means that the page allocator will *not* > > allocate from this migratetype if at least one of the following is true: > > > > - The allocation also needs metadata to be allocated. > > - The allocation isn't movable. A metadata page storing data must be > > able to be migrated at any given time so it can be repurposed to store > > metadata. > > > > Both cases are specific to arm64's implementation of memory metadata. > > > > For now, metadata storage pages management is disabled, and it will be > > enabled once the architecture-specific handling is added. > > > > Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com> > > --- > > [..] > > @@ -2144,6 +2156,15 @@ __rmqueue(struct zone *zone, unsigned int order, int migratetype, > > if (alloc_flags & ALLOC_CMA) > > page = __rmqueue_cma_fallback(zone, order); > > > > + /* > > + * Allocate data pages from MIGRATE_METADATA only if the regular > > + * allocation path fails to increase the chance that the > > + * metadata page is available when the associated data page > > + * needs it. > > + */ > > + if (!page && (alloc_flags & ALLOC_FROM_METADATA)) > > + page = __rmqueue_metadata_fallback(zone, order); > > + > > Hi! > > I guess it would cause non-movable page starving issue as CMA. I don't understand what you mean by "non-movable page starving issue as CMA". Would you care to elaborate? > The metadata pages cannot be used for non-movable allocations. > Metadata pages are utilized poorly, non-movable allocations may end up > getting starved if all regular movable pages are allocated and the only > pages left are metadata. If the system has a lot of CMA pages, then > this problem would become more bad. I think it would be better to make > use of it in places where performance is not critical, including some > GFP_METADATA ? GFP_METADATA pages must be used only for movable allocations. The kernel must be able to migrate GFP_METADATA pages (if they have been allocated) when they are reserved to serve as tag storage for a newly allocated tagged page. If you are referring to the fact that GFP_METADATA pages are allocated only when there are no more free pages in the zone, then yes, I can understand that that might be an issue. However, it's worth keeping in mind that if a GFP_METADATA page is in use when it needs to be repurposed to serve as tag storage, its contents must be migrated first, and this is obviously slow. To put it another way, the more eager the page allocator is to allocate from GFP_METADATA, the slower it will be to allocate tagged pages because reserving the corresponding tag storage will be slow due to migration. Before making a decision, I think it would be very helpful to run performance tests with different allocation policies for GFP_METADATA. But I would say that it's a bit premature for that, and I think it would be best to wait until the series stabilizes. And thank you for the feedback! Alex > > Thanks, > Hyesoo Yu.
On Mon, Oct 16, 2023 at 01:40:39PM +0100, Alexandru Elisei wrote: > Hello, > > On Thu, Oct 12, 2023 at 10:28:24AM +0900, Hyesoo Yu wrote: > > On Wed, Aug 23, 2023 at 02:13:17PM +0100, Alexandru Elisei wrote: > > > Some architectures implement hardware memory coloring to catch incorrect > > > usage of memory allocation. One such architecture is arm64, which calls its > > > hardware implementation Memory Tagging Extension. > > > > > > So far, the memory which stores the metadata has been configured by > > > firmware and hidden from Linux. For arm64, it is impossible to to have the > > > entire system RAM allocated with metadata because executable memory cannot > > > be tagged. Furthermore, in practice, only a chunk of all the memory that > > > can have tags is actually used as tagged. which leaves a portion of > > > metadata memory unused. As such, it would be beneficial to use this memory, > > > which so far has been unaccessible to Linux, to service allocation > > > requests. To prepare for exposing this metadata memory a new migratetype is > > > being added to the page allocator, called MIGRATE_METADATA. > > > > > > One important aspect is that for arm64 the memory that stores metadata > > > cannot have metadata associated with it, it can only be used to store > > > metadata for other pages. This means that the page allocator will *not* > > > allocate from this migratetype if at least one of the following is true: > > > > > > - The allocation also needs metadata to be allocated. > > > - The allocation isn't movable. A metadata page storing data must be > > > able to be migrated at any given time so it can be repurposed to store > > > metadata. > > > > > > Both cases are specific to arm64's implementation of memory metadata. > > > > > > For now, metadata storage pages management is disabled, and it will be > > > enabled once the architecture-specific handling is added. > > > > > > Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com> > > > --- > > > [..] > > > @@ -2144,6 +2156,15 @@ __rmqueue(struct zone *zone, unsigned int order, int migratetype, > > > if (alloc_flags & ALLOC_CMA) > > > page = __rmqueue_cma_fallback(zone, order); > > > > > > + /* > > > + * Allocate data pages from MIGRATE_METADATA only if the regular > > > + * allocation path fails to increase the chance that the > > > + * metadata page is available when the associated data page > > > + * needs it. > > > + */ > > > + if (!page && (alloc_flags & ALLOC_FROM_METADATA)) > > > + page = __rmqueue_metadata_fallback(zone, order); > > > + > > > > Hi! > > > > I guess it would cause non-movable page starving issue as CMA. > > I don't understand what you mean by "non-movable page starving issue as > CMA". Would you care to elaborate? > Before below patch, I frequently encountered situations where there was free CMA memory available but the allocation of unmovable page failed. That patch has improved this issue. ("mm,page_alloc,cma: conditionally prefer cma pageblocks for movable allocations) https://lore.kernel.org/linux-mm/20200306150102.3e77354b@imladris.surriel.com/ I guess it would be beneficial to add a policy for effectively utilizing the metadata area as well. I think migration is cheaper than app killing or swap in terms of performance. But, if the next iteration tries to use only cma, as discussed in recent mailing lists, I think this concern would be fine. Thanks, Regards. > > The metadata pages cannot be used for non-movable allocations. > > Metadata pages are utilized poorly, non-movable allocations may end up > > getting starved if all regular movable pages are allocated and the only > > pages left are metadata. If the system has a lot of CMA pages, then > > this problem would become more bad. I think it would be better to make > > use of it in places where performance is not critical, including some > > GFP_METADATA ? > > GFP_METADATA pages must be used only for movable allocations. The kernel > must be able to migrate GFP_METADATA pages (if they have been allocated) > when they are reserved to serve as tag storage for a newly allocated tagged > page. > > If you are referring to the fact that GFP_METADATA pages are allocated only > when there are no more free pages in the zone, then yes, I can understand > that that might be an issue. However, it's worth keeping in mind that if a > GFP_METADATA page is in use when it needs to be repurposed to serve as tag > storage, its contents must be migrated first, and this is obviously slow. > > To put it another way, the more eager the page allocator is to allocate > from GFP_METADATA, the slower it will be to allocate tagged pages because > reserving the corresponding tag storage will be slow due to migration. > > Before making a decision, I think it would be very helpful to run > performance tests with different allocation policies for GFP_METADATA. But I > would say that it's a bit premature for that, and I think it would be best > to wait until the series stabilizes. > > And thank you for the feedback! > > Alex > > > > > Thanks, > > Hyesoo Yu. >
diff --git a/arch/arm64/include/asm/memory_metadata.h b/arch/arm64/include/asm/memory_metadata.h new file mode 100644 index 000000000000..5269be7f455f --- /dev/null +++ b/arch/arm64/include/asm/memory_metadata.h @@ -0,0 +1,21 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (C) 2023 ARM Ltd. + */ +#ifndef __ASM_MEMORY_METADATA_H +#define __ASM_MEMORY_METADATA_H + +#include <asm-generic/memory_metadata.h> + +#ifdef CONFIG_MEMORY_METADATA +static inline bool metadata_storage_enabled(void) +{ + return false; +} +static inline bool alloc_can_use_metadata_pages(gfp_t gfp_mask) +{ + return false; +} +#endif /* CONFIG_MEMORY_METADATA */ + +#endif /* __ASM_MEMORY_METADATA_H */ diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index 0ca89ebcdc63..1ca421c11ebc 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -13,6 +13,7 @@ #include <linux/kfence.h> #include <linux/signal.h> #include <linux/mm.h> +#include <linux/mmzone.h> #include <linux/hardirq.h> #include <linux/init.h> #include <linux/kasan.h> @@ -956,6 +957,8 @@ struct folio *vma_alloc_zeroed_movable_folio(struct vm_area_struct *vma, void tag_clear_highpage(struct page *page) { + /* Tag storage pages cannot be tagged. */ + WARN_ON_ONCE(is_migrate_metadata_page(page)); /* Newly allocated page, shouldn't have been tagged yet */ WARN_ON_ONCE(!try_page_mte_tagging(page)); mte_zero_clear_page_tags(page_address(page)); diff --git a/include/asm-generic/Kbuild b/include/asm-generic/Kbuild index 941be574bbe0..048ecffc430c 100644 --- a/include/asm-generic/Kbuild +++ b/include/asm-generic/Kbuild @@ -36,6 +36,7 @@ mandatory-y += kprobes.h mandatory-y += linkage.h mandatory-y += local.h mandatory-y += local64.h +mandatory-y += memory_metadata.h mandatory-y += mmiowb.h mandatory-y += mmu.h mandatory-y += mmu_context.h diff --git a/include/asm-generic/memory_metadata.h b/include/asm-generic/memory_metadata.h new file mode 100644 index 000000000000..dc0c84408a8e --- /dev/null +++ b/include/asm-generic/memory_metadata.h @@ -0,0 +1,18 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __ASM_GENERIC_MEMORY_METADATA_H +#define __ASM_GENERIC_MEMORY_METADATA_H + +#include <linux/gfp.h> + +#ifndef CONFIG_MEMORY_METADATA +static inline bool metadata_storage_enabled(void) +{ + return false; +} +static inline bool alloc_can_use_metadata_pages(gfp_t gfp_mask) +{ + return false; +} +#endif /* !CONFIG_MEMORY_METADATA */ + +#endif /* __ASM_GENERIC_MEMORY_METADATA_H */ diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 5e50b78d58ea..74925806687e 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -61,6 +61,9 @@ enum migratetype { */ MIGRATE_CMA, #endif +#ifdef CONFIG_MEMORY_METADATA + MIGRATE_METADATA, +#endif #ifdef CONFIG_MEMORY_ISOLATION MIGRATE_ISOLATE, /* can't allocate from here */ #endif @@ -78,6 +81,14 @@ extern const char * const migratetype_names[MIGRATE_TYPES]; # define is_migrate_cma_page(_page) false #endif +#ifdef CONFIG_MEMORY_METADATA +# define is_migrate_metadata(migratetype) unlikely((migratetype) == MIGRATE_METADATA) +# define is_migrate_metadata_page(_page) (get_pageblock_migratetype(_page) == MIGRATE_METADATA) +#else +# define is_migrate_metadata(migratetype) false +# define is_migrate_metadata_page(_page) false +#endif + static inline bool is_migrate_movable(int mt) { return is_migrate_cma(mt) || mt == MIGRATE_MOVABLE; diff --git a/mm/Kconfig b/mm/Kconfig index 09130434e30d..838193522e20 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -1236,6 +1236,9 @@ config LOCK_MM_AND_FIND_VMA bool depends on !STACK_GROWSUP +config MEMORY_METADATA + bool + source "mm/damon/Kconfig" endmenu diff --git a/mm/internal.h b/mm/internal.h index a7d9e980429a..efd52c9f1578 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -824,6 +824,11 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone, #define ALLOC_NOFRAGMENT 0x0 #endif #define ALLOC_HIGHATOMIC 0x200 /* Allows access to MIGRATE_HIGHATOMIC */ +#ifdef CONFIG_MEMORY_METADATA +#define ALLOC_FROM_METADATA 0x400 /* allow allocations from MIGRATE_METADATA list */ +#else +#define ALLOC_FROM_METADATA 0x0 +#endif #define ALLOC_KSWAPD 0x800 /* allow waking of kswapd, __GFP_KSWAPD_RECLAIM set */ /* Flags that allow allocations below the min watermark. */ diff --git a/mm/page_alloc.c b/mm/page_alloc.c index fdc230440a44..7baa78abf351 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -53,6 +53,7 @@ #include <linux/khugepaged.h> #include <linux/delayacct.h> #include <asm/div64.h> +#include <asm/memory_metadata.h> #include "internal.h" #include "shuffle.h" #include "page_reporting.h" @@ -1645,6 +1646,17 @@ static inline struct page *__rmqueue_cma_fallback(struct zone *zone, unsigned int order) { return NULL; } #endif +#ifdef CONFIG_MEMORY_METADATA +static __always_inline struct page *__rmqueue_metadata_fallback(struct zone *zone, + unsigned int order) +{ + return __rmqueue_smallest(zone, order, MIGRATE_METADATA); +} +#else +static inline struct page *__rmqueue_metadata_fallback(struct zone *zone, + unsigned int order) { return NULL; } +#endif + /* * Move the free pages in a range to the freelist tail of the requested type. * Note that start_page and end_pages are not aligned on a pageblock @@ -2144,6 +2156,15 @@ __rmqueue(struct zone *zone, unsigned int order, int migratetype, if (alloc_flags & ALLOC_CMA) page = __rmqueue_cma_fallback(zone, order); + /* + * Allocate data pages from MIGRATE_METADATA only if the regular + * allocation path fails to increase the chance that the + * metadata page is available when the associated data page + * needs it. + */ + if (!page && (alloc_flags & ALLOC_FROM_METADATA)) + page = __rmqueue_metadata_fallback(zone, order); + if (!page && __rmqueue_fallback(zone, order, migratetype, alloc_flags)) goto retry; @@ -3088,6 +3109,13 @@ static inline unsigned int gfp_to_alloc_flags_fast(gfp_t gfp_mask, if (gfp_migratetype(gfp_mask) == MIGRATE_MOVABLE) alloc_flags |= ALLOC_CMA; #endif +#ifdef CONFIG_MEMORY_METADATA + if (metadata_storage_enabled() && + gfp_migratetype(gfp_mask) == MIGRATE_MOVABLE && + alloc_can_use_metadata_pages(gfp_mask)) + alloc_flags |= ALLOC_FROM_METADATA; +#endif + return alloc_flags; }
Some architectures implement hardware memory coloring to catch incorrect usage of memory allocation. One such architecture is arm64, which calls its hardware implementation Memory Tagging Extension. So far, the memory which stores the metadata has been configured by firmware and hidden from Linux. For arm64, it is impossible to to have the entire system RAM allocated with metadata because executable memory cannot be tagged. Furthermore, in practice, only a chunk of all the memory that can have tags is actually used as tagged. which leaves a portion of metadata memory unused. As such, it would be beneficial to use this memory, which so far has been unaccessible to Linux, to service allocation requests. To prepare for exposing this metadata memory a new migratetype is being added to the page allocator, called MIGRATE_METADATA. One important aspect is that for arm64 the memory that stores metadata cannot have metadata associated with it, it can only be used to store metadata for other pages. This means that the page allocator will *not* allocate from this migratetype if at least one of the following is true: - The allocation also needs metadata to be allocated. - The allocation isn't movable. A metadata page storing data must be able to be migrated at any given time so it can be repurposed to store metadata. Both cases are specific to arm64's implementation of memory metadata. For now, metadata storage pages management is disabled, and it will be enabled once the architecture-specific handling is added. Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com> --- arch/arm64/include/asm/memory_metadata.h | 21 ++++++++++++++++++ arch/arm64/mm/fault.c | 3 +++ include/asm-generic/Kbuild | 1 + include/asm-generic/memory_metadata.h | 18 +++++++++++++++ include/linux/mmzone.h | 11 ++++++++++ mm/Kconfig | 3 +++ mm/internal.h | 5 +++++ mm/page_alloc.c | 28 ++++++++++++++++++++++++ 8 files changed, 90 insertions(+) create mode 100644 arch/arm64/include/asm/memory_metadata.h create mode 100644 include/asm-generic/memory_metadata.h