[v3,5/5] alloc_tag: config to store page allocation tag refs in page flags

Message ID	20241014203646.1952505-6-surenb@google.com (mailing list archive)
State	New
Headers	show Return-Path: <owner-linux-mm@kvack.org> Date: Mon, 14 Oct 2024 13:36:46 -0700 In-Reply-To: <20241014203646.1952505-1-surenb@google.com> Mime-Version: 1.0 References: <20241014203646.1952505-1-surenb@google.com> Message-ID: <20241014203646.1952505-6-surenb@google.com> Subject: [PATCH v3 5/5] alloc_tag: config to store page allocation tag refs in page flags From: Suren Baghdasaryan <surenb@google.com> To: akpm@linux-foundation.org Cc: kent.overstreet@linux.dev, corbet@lwn.net, arnd@arndb.de, mcgrof@kernel.org, rppt@kernel.org, paulmck@kernel.org, thuth@redhat.com, tglx@linutronix.de, bp@alien8.de, xiongwei.song@windriver.com, ardb@kernel.org, david@redhat.com, vbabka@suse.cz, mhocko@suse.com, hannes@cmpxchg.org, roman.gushchin@linux.dev, dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com, pasha.tatashin@soleen.com, souravpanda@google.com, keescook@chromium.org, dennis@kernel.org, jhubbard@nvidia.com, yuzhao@google.com, vvvvvv@google.com, rostedt@goodmis.org, iamjoonsoo.kim@lge.com, rientjes@google.com, minchan@google.com, kaleshsingh@google.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-modules@vger.kernel.org, kernel-team@android.com, surenb@google.com Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org Precedence: bulk
Series	page allocation tag compression \| expand [v3,0/5] page allocation tag compression [v3,1/5] maple_tree: add mas_for_each_rev() helper [v3,2/5] alloc_tag: load module tags into separate contiguous memory [v3,3/5] alloc_tag: populate memory for module tags as needed [v3,4/5] alloc_tag: introduce pgalloc_tag_ref to abstract page tag references [v3,5/5] alloc_tag: config to store page allocation tag refs in page flags

diff --git a/include/linux/alloc_tag.h b/include/linux/alloc_tag.h index 7431757999c5..4f811ec0ffe0 100644 --- a/include/linux/alloc_tag.h +++ b/include/linux/alloc_tag.h @@ -30,8 +30,16 @@ struct alloc_tag { struct alloc_tag_counters __percpu *counters; } __aligned(8); +struct alloc_tag_kernel_section { + struct alloc_tag *first_tag; + unsigned long count; +}; + struct alloc_tag_module_section { - unsigned long start_addr; + union { + unsigned long start_addr; + struct alloc_tag *first_tag; + }; unsigned long end_addr; /* used size */ unsigned long size; diff --git a/include/linux/codetag.h b/include/linux/codetag.h index fb4e7adfa746..401fc297eeda 100644 --- a/include/linux/codetag.h +++ b/include/linux/codetag.h @@ -13,6 +13,9 @@ struct codetag_module; struct seq_buf; struct module; +#define CODETAG_SECTION_START_PREFIX "__start_" +#define CODETAG_SECTION_STOP_PREFIX "__stop_" + /* * An instance of this structure is created in a special ELF section at every * code location being tagged. At runtime, the special section is treated as diff --git a/include/linux/page-flags-layout.h b/include/linux/page-flags-layout.h index 7d79818dc065..4f5c9e979bb9 100644 --- a/include/linux/page-flags-layout.h +++ b/include/linux/page-flags-layout.h @@ -111,5 +111,12 @@ ZONES_WIDTH - LRU_GEN_WIDTH - SECTIONS_WIDTH - \ NODES_WIDTH - KASAN_TAG_WIDTH - LAST_CPUPID_WIDTH) +#define NR_NON_PAGEFLAG_BITS (SECTIONS_WIDTH + NODES_WIDTH + ZONES_WIDTH + \ + LAST_CPUPID_SHIFT + KASAN_TAG_WIDTH + \ + LRU_GEN_WIDTH + LRU_REFS_WIDTH) + +#define NR_UNUSED_PAGEFLAG_BITS (BITS_PER_LONG - \ + (NR_NON_PAGEFLAG_BITS + NR_PAGEFLAGS)) + #endif #endif /* _LINUX_PAGE_FLAGS_LAYOUT */ diff --git a/include/linux/pgalloc_tag.h b/include/linux/pgalloc_tag.h index bc65710ee1f9..69976cf747a6 100644 --- a/include/linux/pgalloc_tag.h +++ b/include/linux/pgalloc_tag.h @@ -9,6 +9,93 @@ #ifdef CONFIG_MEM_ALLOC_PROFILING +#ifdef CONFIG_PGALLOC_TAG_USE_PAGEFLAGS + +typedef u16 pgalloc_tag_ref; + +extern struct alloc_tag_kernel_section kernel_tags; + +#define CODETAG_ID_NULL 0 +#define CODETAG_ID_EMPTY 1 +#define CODETAG_ID_FIRST 2 + +#ifdef CONFIG_MODULES + +extern struct alloc_tag_module_section module_tags; + +static inline struct codetag *get_module_ct(pgalloc_tag_ref pgref) +{ + return &module_tags.first_tag[pgref - kernel_tags.count].ct; +} + +static inline pgalloc_tag_ref get_module_pgref(struct alloc_tag *tag) +{ + return CODETAG_ID_FIRST + kernel_tags.count + (tag - module_tags.first_tag); +} + +#else /* CONFIG_MODULES */ + +static inline struct codetag *get_module_ct(pgalloc_tag_ref pgref) +{ + pr_warn("invalid page tag reference %lu\n", (unsigned long)pgref); + return NULL; +} + +static inline pgalloc_tag_ref get_module_pgref(struct alloc_tag *tag) +{ + pr_warn("invalid page tag 0x%lx\n", (unsigned long)tag); + return CODETAG_ID_NULL; +} + +#endif /* CONFIG_MODULES */ + +static inline void read_pgref(pgalloc_tag_ref *pgref, union codetag_ref *ref) +{ + pgalloc_tag_ref pgref_val = *pgref; + + switch (pgref_val) { + case (CODETAG_ID_NULL): + ref->ct = NULL; + break; + case (CODETAG_ID_EMPTY): + set_codetag_empty(ref); + break; + default: + pgref_val -= CODETAG_ID_FIRST; + ref->ct = pgref_val < kernel_tags.count ? + &kernel_tags.first_tag[pgref_val].ct : + get_module_ct(pgref_val); + break; + } +} + +static inline void write_pgref(pgalloc_tag_ref *pgref, union codetag_ref *ref) +{ + struct alloc_tag *tag; + + if (!ref->ct) { + *pgref = CODETAG_ID_NULL; + return; + } + + if (is_codetag_empty(ref)) { + *pgref = CODETAG_ID_EMPTY; + return; + } + + tag = ct_to_alloc_tag(ref->ct); + if (tag >= kernel_tags.first_tag && tag < kernel_tags.first_tag + kernel_tags.count) { + *pgref = CODETAG_ID_FIRST + (tag - kernel_tags.first_tag); + return; + } + + *pgref = get_module_pgref(tag); +} + +void __init alloc_tag_sec_init(void); + +#else /* CONFIG_PGALLOC_TAG_USE_PAGEFLAGS */ + typedef union codetag_ref pgalloc_tag_ref; static inline void read_pgref(pgalloc_tag_ref *pgref, union codetag_ref *ref) @@ -21,8 +108,13 @@ static inline void write_pgref(pgalloc_tag_ref *pgref, union codetag_ref *ref) pgref->ct = ref->ct; } +static inline void alloc_tag_sec_init(void) {} + +#endif /* CONFIG_PGALLOC_TAG_USE_PAGEFLAGS */ + union pgtag_ref_handle { pgalloc_tag_ref *pgref; /* reference in page extension */ + struct page *page; /* reference in page flags */ }; #include <linux/page_ext.h> @@ -40,8 +132,8 @@ static inline struct page_ext *page_ext_from_pgref(pgalloc_tag_ref *pgref) } /* Should be called only if mem_alloc_profiling_enabled() */ -static inline bool get_page_tag_ref(struct page *page, union codetag_ref *ref, - union pgtag_ref_handle *handle) +static inline bool page_ext_get_page_tag_ref(struct page *page, union codetag_ref *ref, + union pgtag_ref_handle *handle) { struct page_ext *page_ext; pgalloc_tag_ref *pgref; @@ -59,7 +151,7 @@ static inline bool get_page_tag_ref(struct page *page, union codetag_ref *ref, return true; } -static inline void put_page_tag_ref(union pgtag_ref_handle handle) +static inline void page_ext_put_page_tag_ref(union pgtag_ref_handle handle) { if (WARN_ON(!handle.pgref)) return; @@ -67,8 +159,8 @@ static inline void put_page_tag_ref(union pgtag_ref_handle handle) page_ext_put(page_ext_from_pgref(handle.pgref)); } -static inline void update_page_tag_ref(union pgtag_ref_handle handle, - union codetag_ref *ref) +static inline void page_ext_update_page_tag_ref(union pgtag_ref_handle handle, + union codetag_ref *ref) { if (WARN_ON(!handle.pgref || !ref)) return; @@ -76,6 +168,87 @@ static inline void update_page_tag_ref(union pgtag_ref_handle handle, write_pgref(handle.pgref, ref); } +#ifdef CONFIG_PGALLOC_TAG_USE_PAGEFLAGS + +DECLARE_STATIC_KEY_TRUE(mem_profiling_use_pageflags); +extern unsigned long alloc_tag_ref_mask; +extern int alloc_tag_ref_offs; + +/* Should be called only if mem_alloc_profiling_enabled() */ +static inline bool get_page_tag_ref(struct page *page, union codetag_ref *ref, + union pgtag_ref_handle *handle) +{ + pgalloc_tag_ref pgref; + + if (!static_key_enabled(&mem_profiling_use_pageflags)) + return page_ext_get_page_tag_ref(page, ref, handle); + + if (!page) + return false; + + pgref = (page->flags >> alloc_tag_ref_offs) & alloc_tag_ref_mask; + read_pgref(&pgref, ref); + handle->page = page; + return true; +} + +static inline void put_page_tag_ref(union pgtag_ref_handle handle) +{ + if (!static_key_enabled(&mem_profiling_use_pageflags)) { + page_ext_put_page_tag_ref(handle); + return; + } + + WARN_ON(!handle.page); +} + +static inline void update_page_tag_ref(union pgtag_ref_handle handle, union codetag_ref *ref) +{ + unsigned long old_flags, flags, val; + struct page *page = handle.page; + pgalloc_tag_ref pgref; + + if (!static_key_enabled(&mem_profiling_use_pageflags)) { + page_ext_update_page_tag_ref(handle, ref); + return; + } + + if (WARN_ON(!page || !ref)) + return; + + write_pgref(&pgref, ref); + val = (unsigned long)pgref; + val = (val & alloc_tag_ref_mask) << alloc_tag_ref_offs; + do { + old_flags = READ_ONCE(page->flags); + flags = old_flags; + flags &= ~(alloc_tag_ref_mask << alloc_tag_ref_offs); + flags |= val; + } while (unlikely(!try_cmpxchg(&page->flags, &old_flags, flags))); +} + +#else /* CONFIG_PGALLOC_TAG_USE_PAGEFLAGS */ + +/* Should be called only if mem_alloc_profiling_enabled() */ +static inline bool get_page_tag_ref(struct page *page, union codetag_ref *ref, + union pgtag_ref_handle *handle) +{ + return page_ext_get_page_tag_ref(page, ref, handle); +} + +static inline void put_page_tag_ref(union pgtag_ref_handle handle) +{ + page_ext_put_page_tag_ref(handle); +} + +static inline void update_page_tag_ref(union pgtag_ref_handle handle, + union codetag_ref *ref) +{ + page_ext_update_page_tag_ref(handle, ref); +} + +#endif /* CONFIG_PGALLOC_TAG_USE_PAGEFLAGS */ + static inline void clear_page_tag_ref(struct page *page) { if (mem_alloc_profiling_enabled()) { @@ -152,6 +325,7 @@ static inline void pgalloc_tag_add(struct page *page, struct task_struct *task, static inline void pgalloc_tag_sub(struct page *page, unsigned int nr) {} static inline struct alloc_tag *pgalloc_tag_get(struct page *page) { return NULL; } static inline void pgalloc_tag_sub_pages(struct alloc_tag *tag, unsigned int nr) {} +static inline void alloc_tag_sec_init(void) {} #endif /* CONFIG_MEM_ALLOC_PROFILING */ diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 7315f643817a..f4c272c30719 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1017,6 +1017,25 @@ config MEM_ALLOC_PROFILING_DEBUG Adds warnings with helpful error messages for memory allocation profiling. +config PGALLOC_TAG_USE_PAGEFLAGS + bool "Use pageflags to encode page allocation tag reference" + default n + depends on MEM_ALLOC_PROFILING + help + When set, page allocation tag references are encoded inside page + flags if they fit, otherwise they are encoded in page extensions. + + Setting this flag reduces memory and performance overhead of memory + allocation profiling but it requires enough unused page flag bits to + address all kernel allocations. If enabled but there are not enough + unused page flag bits, profiling will fall back to using page + extensions and a warning will be issued to disable this config. + If dynamically loaded modules add enough tags that they can't be + addressed anymore with available page flag bits, profiling for such + modules will be disabled and a warning will be issued. + + Say N if unsure. + source "lib/Kconfig.kasan" source "lib/Kconfig.kfence" source "lib/Kconfig.kmsan" diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c index 2ef762acc203..341a5c826449 100644 --- a/lib/alloc_tag.c +++ b/lib/alloc_tag.c @@ -3,6 +3,7 @@ #include <linux/execmem.h> #include <linux/fs.h> #include <linux/gfp.h> +#include <linux/kallsyms.h> #include <linux/module.h> #include <linux/page_ext.h> #include <linux/pgalloc_tag.h> @@ -152,6 +153,42 @@ static void __init procfs_init(void) proc_create_seq("allocinfo", 0400, NULL, &allocinfo_seq_op); } +#ifdef CONFIG_PGALLOC_TAG_USE_PAGEFLAGS + +DEFINE_STATIC_KEY_TRUE(mem_profiling_use_pageflags); +unsigned long alloc_tag_ref_mask; +int alloc_tag_ref_offs; + +#define SECTION_START(NAME) (CODETAG_SECTION_START_PREFIX NAME) +#define SECTION_STOP(NAME) (CODETAG_SECTION_STOP_PREFIX NAME) + +struct alloc_tag_kernel_section kernel_tags = { NULL, 0 }; + +void __init alloc_tag_sec_init(void) +{ + struct alloc_tag *last_codetag; + + kernel_tags.first_tag = (struct alloc_tag *)kallsyms_lookup_name( + SECTION_START(ALLOC_TAG_SECTION_NAME)); + last_codetag = (struct alloc_tag *)kallsyms_lookup_name( + SECTION_STOP(ALLOC_TAG_SECTION_NAME)); + kernel_tags.count = last_codetag - kernel_tags.first_tag; + + /* Check if kernel tags fit into page flags */ + if (kernel_tags.count > (1UL << NR_UNUSED_PAGEFLAG_BITS)) { + static_branch_disable(&mem_profiling_use_pageflags); + pr_warn("%lu kernel tags do not fit into %d available page flag bits, page extensions will be used instead!\n", + kernel_tags.count, NR_UNUSED_PAGEFLAG_BITS); + } else { + alloc_tag_ref_offs = (LRU_REFS_PGOFF - NR_UNUSED_PAGEFLAG_BITS); + alloc_tag_ref_mask = ((1UL << NR_UNUSED_PAGEFLAG_BITS) - 1); + pr_info("All unused page flags (%d bits) are used to store page tag references!\n", + NR_UNUSED_PAGEFLAG_BITS); + } +} + +#endif /* CONFIG_PGALLOC_TAG_USE_PAGEFLAGS */ + #ifdef CONFIG_MODULES static struct maple_tree mod_area_mt = MTREE_INIT(mod_area_mt, MT_FLAGS_ALLOC_RANGE); @@ -161,7 +198,29 @@ static struct module unloaded_mod; /* A dummy object used to indicate a module prepended area */ static struct module prepend_mod; -static struct alloc_tag_module_section module_tags; +struct alloc_tag_module_section module_tags; + +#ifdef CONFIG_PGALLOC_TAG_USE_PAGEFLAGS +static inline unsigned long alloc_tag_align(unsigned long val) +{ + if (val % sizeof(struct alloc_tag) == 0) + return val; + return ((val / sizeof(struct alloc_tag)) + 1) * sizeof(struct alloc_tag); +} + +static inline bool tags_addressable(void) +{ + unsigned long tag_idx_count = CODETAG_ID_FIRST + kernel_tags.count + + module_tags.size / sizeof(struct alloc_tag); + + return tag_idx_count < (1UL << NR_UNUSED_PAGEFLAG_BITS); +} + +#else /* CONFIG_PGALLOC_TAG_USE_PAGEFLAGS */ + +static inline bool tags_addressable(void) { return true; } + +#endif /* CONFIG_PGALLOC_TAG_USE_PAGEFLAGS */ static bool needs_section_mem(struct module *mod, unsigned long size) { @@ -237,6 +296,21 @@ static void *reserve_module_tags(struct module *mod, unsigned long size, if (!align) align = 1; +#ifdef CONFIG_PGALLOC_TAG_USE_PAGEFLAGS + /* + * If alloc_tag size is not a multiple of required alignment tag + * indexing does not work. + */ + if (!IS_ALIGNED(sizeof(struct alloc_tag), align)) { + pr_err("%s: alignment %lu is incompatible with allocation tag indexing, disable CONFIG_PGALLOC_TAG_USE_PAGEFLAGS", + mod->name, align); + return ERR_PTR(-EINVAL); + } + + /* Ensure prepend consumes multiple of alloc_tag-sized blocks */ + if (prepend) + prepend = alloc_tag_align(prepend); +#endif /* CONFIG_PGALLOC_TAG_USE_PAGEFLAGS */ mas_lock(&mas); repeat: /* Try finding exact size and hope the start is aligned */ @@ -305,6 +379,12 @@ static void *reserve_module_tags(struct module *mod, unsigned long size, unsigned long phys_size = vm_module_tags->nr_pages << PAGE_SHIFT; module_tags.size = offset + size; + if (!tags_addressable() && mem_alloc_profiling_enabled()) { + static_branch_disable(&mem_alloc_profiling_key); + pr_warn("With module %s there are too many tags to fit in %d page flag bits. Memory profiling is disabled!\n", + mod->name, NR_UNUSED_PAGEFLAG_BITS); + } + if (phys_size < module_tags.size) { int grow_res; @@ -406,6 +486,10 @@ static int __init alloc_mod_tags_mem(void) module_tags.start_addr = (unsigned long)vm_module_tags->addr; module_tags.end_addr = module_tags.start_addr + MODULE_ALLOC_TAG_VMAP_SIZE; +#ifdef CONFIG_PGALLOC_TAG_USE_PAGEFLAGS + /* Ensure the base is alloc_tag aligned */ + module_tags.start_addr = alloc_tag_align(module_tags.start_addr); +#endif return 0; } @@ -467,6 +551,10 @@ early_param("sysctl.vm.mem_profiling", setup_early_mem_profiling); static __init bool need_page_alloc_tagging(void) { +#ifdef CONFIG_PGALLOC_TAG_USE_PAGEFLAGS + if (static_key_enabled(&mem_profiling_use_pageflags)) + return false; +#endif return mem_profiling_support; } diff --git a/lib/codetag.c b/lib/codetag.c index 3f3a4f4ca72d..cda5a852ef30 100644 --- a/lib/codetag.c +++ b/lib/codetag.c @@ -149,8 +149,8 @@ static struct codetag_range get_section_range(struct module *mod, const char *section) { return (struct codetag_range) { - get_symbol(mod, "__start_", section), - get_symbol(mod, "__stop_", section), + get_symbol(mod, CODETAG_SECTION_START_PREFIX, section), + get_symbol(mod, CODETAG_SECTION_STOP_PREFIX, section), }; } diff --git a/mm/mm_init.c b/mm/mm_init.c index 4ba5607aaf19..1c205b0a86ed 100644 --- a/mm/mm_init.c +++ b/mm/mm_init.c @@ -83,8 +83,7 @@ void __init mminit_verify_pageflags_layout(void) unsigned long or_mask, add_mask; shift = BITS_PER_LONG; - width = shift - SECTIONS_WIDTH - NODES_WIDTH - ZONES_WIDTH - - LAST_CPUPID_SHIFT - KASAN_TAG_WIDTH - LRU_GEN_WIDTH - LRU_REFS_WIDTH; + width = shift - NR_NON_PAGEFLAG_BITS; mminit_dprintk(MMINIT_TRACE, "pageflags_layout_widths", "Section %d Node %d Zone %d Lastcpupid %d Kasantag %d Gen %d Tier %d Flags %d\n", SECTIONS_WIDTH, @@ -2639,7 +2638,7 @@ void __init mm_core_init(void) BUILD_BUG_ON(MAX_ZONELISTS > 2); build_all_zonelists(NULL); page_alloc_init_cpuhp(); - + alloc_tag_sec_init(); /* * page_ext requires contiguous pages, * bigger than MAX_PAGE_ORDER unless SPARSEMEM.

[v3,5/5] alloc_tag: config to store page allocation tag refs in page flags

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