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Thu, 01 Sep 2022 04:42:55 +0000 From: Oscar Salvador To: Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Michal Hocko , Vlastimil Babka , Eric Dumazet , Waiman Long , Suren Baghdasaryan , Oscar Salvador Subject: [PATCH 1/3] lib/stackdepot: Add a refcount field in stack_record Date: Thu, 1 Sep 2022 06:42:47 +0200 Message-Id: <20220901044249.4624-2-osalvador@suse.de> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220901044249.4624-1-osalvador@suse.de> References: <20220901044249.4624-1-osalvador@suse.de> MIME-Version: 1.0 ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1662007377; a=rsa-sha256; cv=none; b=LZmire8lNa4cF07elFiaMvSvCiSfOGJpW5SsnsYQ0qDBdeWAXv/nyUF3tWTAHoaYRCrF8l 8oPUEt/A6wLo8Y0j2uqEASY0r498c5/4onAY9CIQgtfXh4xhtfpt2+Ri6oODezoPsmPgzY scgjOhzNapl6Zw94DHzkiifmNQvkoa4= ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=pass header.d=suse.de header.s=susede2_rsa header.b=oqUP1He7; dkim=pass header.d=suse.de header.s=susede2_ed25519 header.b=JHXCx1Xe; 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spf=pass (imf12.hostedemail.com: domain of osalvador@suse.de designates 195.135.220.28 as permitted sender) smtp.mailfrom=osalvador@suse.de; dmarc=pass (policy=none) header.from=suse.de X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1662007377-806559 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: We want to filter out page_owner output and print only those stacks that have been repeated beyond a certain threshold. This gives us the chance to get rid of a lot of noise. In order to do that, we need to keep track of how many repeated stacks (for allocation) do we have, so we add a new refcount_t field in the stack_record struct. Note that on __set_page_owner_handle(), page_owner->handle is set, and on __reset_page_owner(), page_owner->free_handle is set. We are interested in page_owner->handle, so when __set_page_owner() gets called, we derive the stack_record struct from page_owner->handle, and we increment its refcount_t field; and when __reset_page_owner() gets called, we derive its stack_record from page_owner->handle() and we decrement its refcount_t field. This is a preparation for patch#2. Signed-off-by: Oscar Salvador --- include/linux/stackdepot.h | 13 ++++++- lib/stackdepot.c | 79 +++++++++++++++++++++++++++++++------- mm/kasan/common.c | 3 +- mm/page_owner.c | 13 +++++-- 4 files changed, 88 insertions(+), 20 deletions(-) diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h index bc2797955de9..5ee0cf5be88f 100644 --- a/include/linux/stackdepot.h +++ b/include/linux/stackdepot.h @@ -15,9 +15,16 @@ typedef u32 depot_stack_handle_t; +typedef enum stack_action { + STACK_ACTION_NONE, + STACK_ACTION_INC, +}stack_action_t; + depot_stack_handle_t __stack_depot_save(unsigned long *entries, unsigned int nr_entries, - gfp_t gfp_flags, bool can_alloc); + gfp_t gfp_flags, bool can_alloc, + stack_action_t action); +void stack_depot_dec_count(depot_stack_handle_t handle); /* * Every user of stack depot has to call stack_depot_init() during its own init @@ -55,6 +62,10 @@ static inline int stack_depot_early_init(void) { return 0; } depot_stack_handle_t stack_depot_save(unsigned long *entries, unsigned int nr_entries, gfp_t gfp_flags); +depot_stack_handle_t stack_depot_save_action(unsigned long *entries, + unsigned int nr_entries, + gfp_t gfp_flags, + stack_action_t action); unsigned int stack_depot_fetch(depot_stack_handle_t handle, unsigned long **entries); diff --git a/lib/stackdepot.c b/lib/stackdepot.c index 5ca0d086ef4a..aeb59d3557e2 100644 --- a/lib/stackdepot.c +++ b/lib/stackdepot.c @@ -63,6 +63,7 @@ struct stack_record { u32 hash; /* Hash in the hastable */ u32 size; /* Number of frames in the stack */ union handle_parts handle; + refcount_t count; /* Number of the same repeated stacks */ unsigned long entries[]; /* Variable-sized array of entries. */ }; @@ -139,6 +140,7 @@ depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc) stack->handle.slabindex = depot_index; stack->handle.offset = depot_offset >> STACK_ALLOC_ALIGN; stack->handle.valid = 1; + refcount_set(&stack->count, 1); memcpy(stack->entries, entries, flex_array_size(stack, entries, size)); depot_offset += required_size; @@ -302,6 +304,29 @@ void stack_depot_print(depot_stack_handle_t stack) } EXPORT_SYMBOL_GPL(stack_depot_print); +static struct stack_record *stack_depot_getstack(depot_stack_handle_t handle) +{ + union handle_parts parts = { .handle = handle }; + void *slab; + size_t offset = parts.offset << STACK_ALLOC_ALIGN; + struct stack_record *stack; + + if(!handle) + return NULL; + + if (parts.slabindex > depot_index) { + WARN(1, "slab index %d out of bounds (%d) for stack id %08x\n", + parts.slabindex, depot_index, handle); + return NULL; + } + slab = stack_slabs[parts.slabindex]; + if (!slab) + return NULL; + + stack = slab + offset; + return stack; +} + /** * stack_depot_fetch - Fetch stack entries from a depot * @@ -314,30 +339,42 @@ EXPORT_SYMBOL_GPL(stack_depot_print); unsigned int stack_depot_fetch(depot_stack_handle_t handle, unsigned long **entries) { - union handle_parts parts = { .handle = handle }; - void *slab; - size_t offset = parts.offset << STACK_ALLOC_ALIGN; struct stack_record *stack; *entries = NULL; if (!handle) return 0; - if (parts.slabindex > depot_index) { - WARN(1, "slab index %d out of bounds (%d) for stack id %08x\n", - parts.slabindex, depot_index, handle); - return 0; - } - slab = stack_slabs[parts.slabindex]; - if (!slab) + stack = stack_depot_getstack(handle); + if (!stack) return 0; - stack = slab + offset; *entries = stack->entries; return stack->size; } EXPORT_SYMBOL_GPL(stack_depot_fetch); +static void stack_depot_inc_count(struct stack_record *stack) +{ + refcount_inc(&stack->count); +} + +void stack_depot_dec_count(depot_stack_handle_t handle) +{ + struct stack_record *stack = NULL; + + stack = stack_depot_getstack(handle); + if (stack) { + /* + * page_owner creates some stacks via create_dummy_stack(). + * We are not interested in those, so make sure we only decrement + * "valid" stacks. + */ + if (refcount_read(&stack->count) > 1) + refcount_dec(&stack->count); + } +} + /** * __stack_depot_save - Save a stack trace from an array * @@ -363,7 +400,8 @@ EXPORT_SYMBOL_GPL(stack_depot_fetch); */ depot_stack_handle_t __stack_depot_save(unsigned long *entries, unsigned int nr_entries, - gfp_t alloc_flags, bool can_alloc) + gfp_t alloc_flags, bool can_alloc, + stack_action_t action) { struct stack_record *found = NULL, **bucket; depot_stack_handle_t retval = 0; @@ -449,8 +487,11 @@ depot_stack_handle_t __stack_depot_save(unsigned long *entries, /* Nobody used this memory, ok to free it. */ free_pages((unsigned long)prealloc, STACK_ALLOC_ORDER); } - if (found) + if (found) { retval = found->handle.handle; + if (action == STACK_ACTION_INC) + stack_depot_inc_count(found); + } fast_exit: return retval; } @@ -472,6 +513,16 @@ depot_stack_handle_t stack_depot_save(unsigned long *entries, unsigned int nr_entries, gfp_t alloc_flags) { - return __stack_depot_save(entries, nr_entries, alloc_flags, true); + return __stack_depot_save(entries, nr_entries, alloc_flags, true, + STACK_ACTION_NONE); } EXPORT_SYMBOL_GPL(stack_depot_save); + +depot_stack_handle_t stack_depot_save_action(unsigned long *entries, + unsigned int nr_entries, + gfp_t alloc_flags, + stack_action_t action) +{ + return __stack_depot_save(entries, nr_entries, alloc_flags, true, action); +} +EXPORT_SYMBOL_GPL(stack_depot_save_action); diff --git a/mm/kasan/common.c b/mm/kasan/common.c index c40c0e7b3b5f..f434994f3b0d 100644 --- a/mm/kasan/common.c +++ b/mm/kasan/common.c @@ -36,7 +36,8 @@ depot_stack_handle_t kasan_save_stack(gfp_t flags, bool can_alloc) unsigned int nr_entries; nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0); - return __stack_depot_save(entries, nr_entries, flags, can_alloc); + return __stack_depot_save(entries, nr_entries, flags, can_alloc, + STACK_ACTION_NONE); } void kasan_set_track(struct kasan_track *track, gfp_t flags) diff --git a/mm/page_owner.c b/mm/page_owner.c index e4c6f3f1695b..794f346d7520 100644 --- a/mm/page_owner.c +++ b/mm/page_owner.c @@ -106,7 +106,7 @@ static inline struct page_owner *get_page_owner(struct page_ext *page_ext) return (void *)page_ext + page_owner_ops.offset; } -static noinline depot_stack_handle_t save_stack(gfp_t flags) +static noinline depot_stack_handle_t save_stack(gfp_t flags, stack_action_t action) { unsigned long entries[PAGE_OWNER_STACK_DEPTH]; depot_stack_handle_t handle; @@ -125,7 +125,7 @@ static noinline depot_stack_handle_t save_stack(gfp_t flags) current->in_page_owner = 1; nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 2); - handle = stack_depot_save(entries, nr_entries, flags); + handle = stack_depot_save_action(entries, nr_entries, flags, action); if (!handle) handle = failure_handle; @@ -138,6 +138,7 @@ void __reset_page_owner(struct page *page, unsigned short order) int i; struct page_ext *page_ext; depot_stack_handle_t handle; + depot_stack_handle_t alloc_handle; struct page_owner *page_owner; u64 free_ts_nsec = local_clock(); @@ -145,7 +146,10 @@ void __reset_page_owner(struct page *page, unsigned short order) if (unlikely(!page_ext)) return; - handle = save_stack(GFP_NOWAIT | __GFP_NOWARN); + page_owner = get_page_owner(page_ext); + alloc_handle = page_owner->handle; + + handle = save_stack(GFP_NOWAIT | __GFP_NOWARN, STACK_ACTION_NONE); for (i = 0; i < (1 << order); i++) { __clear_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags); page_owner = get_page_owner(page_ext); @@ -153,6 +157,7 @@ void __reset_page_owner(struct page *page, unsigned short order) page_owner->free_ts_nsec = free_ts_nsec; page_ext = page_ext_next(page_ext); } + stack_depot_dec_count(alloc_handle); } static inline void __set_page_owner_handle(struct page_ext *page_ext, @@ -189,7 +194,7 @@ noinline void __set_page_owner(struct page *page, unsigned short order, if (unlikely(!page_ext)) return; - handle = save_stack(gfp_mask); + handle = save_stack(gfp_mask, STACK_ACTION_INC); __set_page_owner_handle(page_ext, handle, order, gfp_mask); }