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Mon, 12 Feb 2024 22:29:27 +0000 (UTC) Received: from dovecot-director2.suse.de ([10.150.64.162]) by imap2.dmz-prg2.suse.org with ESMTPSA id CGxaE8ebymX5JgAAn2gu4w (envelope-from ); Mon, 12 Feb 2024 22:29:27 +0000 From: Oscar Salvador To: Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Michal Hocko , Vlastimil Babka , Marco Elver , Andrey Konovalov , Alexander Potapenko , Oscar Salvador Subject: [PATCH v8 2/5] mm,page_owner: Implement the tracking of the stacks count Date: Mon, 12 Feb 2024 23:30:26 +0100 Message-ID: <20240212223029.30769-3-osalvador@suse.de> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240212223029.30769-1-osalvador@suse.de> References: <20240212223029.30769-1-osalvador@suse.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: tbatudbmmnsg64roidx6or93ezucfuwi X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 6897A160005 X-Rspam-User: X-HE-Tag: 1707776970-421498 X-HE-Meta: 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 TQi9Z4NL TNJLr0HdfVArNxj9WlQ98uGmbtjkULRqRSZBQUzqUiXq6wu35FD2V0+58UY0vzx+CajScbsfoBkM+T7INwlxdwc2YyMfCivJ3Xh/FU3SId1YjzTBKwlgFn+BqLpL2aejx8RUHjVeEVG2qLi//OeS7uv1lzhNDNM2Y985bkOFKL1roCHQtZNgvAPpwTESOO+WyGXV1SJocLGIAbJlQwyMoynYB09osbAJ8MgZwyQ2JZYQLlAqzzVZWOPBhkgwocettq1FQ 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: List-Subscribe: List-Unsubscribe: page_owner needs to increment a stack_record refcount when a new allocation occurs, and decrement it on a free operation. In order to do that, we need to have a way to get a stack_record from a handle. Implement __stack_depot_get_stack_record() which just does that, and make it public so page_owner can use it. Also implement {inc,dec}_stack_record_count() which increments or decrements on respective allocation and free operations, via __reset_page_owner() (free operation) and __set_page_owner() (alloc operation). Traversing all stackdepot buckets comes with its own complexity, plus we would have to implement a way to mark only those stack_records that were originated from page_owner, as those are the ones we are interested in. For that reason, page_owner maintains its own list of stack_records, because traversing that list is faster than traversing all buckets while keeping at the same time a low complexity. inc_stack_record_count() is responsible of adding new stack_records into the list stack_list. Modifications on the list are protected via a spinlock with irqs disabled, since this code can also be reached from IRQ context. Signed-off-by: Oscar Salvador --- include/linux/stackdepot.h | 9 +++++ lib/stackdepot.c | 8 +++++ mm/page_owner.c | 73 ++++++++++++++++++++++++++++++++++++++ 3 files changed, 90 insertions(+) diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h index 90274860fd8e..f3c2162bf615 100644 --- a/include/linux/stackdepot.h +++ b/include/linux/stackdepot.h @@ -175,6 +175,15 @@ depot_stack_handle_t stack_depot_save_flags(unsigned long *entries, depot_stack_handle_t stack_depot_save(unsigned long *entries, unsigned int nr_entries, gfp_t gfp_flags); +/** + * __stack_depot_get_stack_record - Get a pointer to a stack_record struct + * This function is only for internal purposes. + * @handle: Stack depot handle + * + * Return: Returns a pointer to a stack_record struct + */ +struct stack_record *__stack_depot_get_stack_record(depot_stack_handle_t handle); + /** * stack_depot_fetch - Fetch a stack trace from stack depot * diff --git a/lib/stackdepot.c b/lib/stackdepot.c index 6f9095374847..fdb09450a538 100644 --- a/lib/stackdepot.c +++ b/lib/stackdepot.c @@ -685,6 +685,14 @@ depot_stack_handle_t stack_depot_save(unsigned long *entries, } EXPORT_SYMBOL_GPL(stack_depot_save); +struct stack_record *__stack_depot_get_stack_record(depot_stack_handle_t handle) +{ + if (!handle) + return NULL; + + return depot_fetch_stack(handle); +} + unsigned int stack_depot_fetch(depot_stack_handle_t handle, unsigned long **entries) { diff --git a/mm/page_owner.c b/mm/page_owner.c index 5634e5d890f8..7d1b3f75cef3 100644 --- a/mm/page_owner.c +++ b/mm/page_owner.c @@ -36,6 +36,14 @@ struct page_owner { pid_t free_tgid; }; +struct stack { + struct stack_record *stack_record; + struct stack *next; +}; + +static struct stack *stack_list; +static DEFINE_SPINLOCK(stack_list_lock); + static bool page_owner_enabled __initdata; DEFINE_STATIC_KEY_FALSE(page_owner_inited); @@ -61,6 +69,57 @@ static __init bool need_page_owner(void) return page_owner_enabled; } +static void add_stack_record_to_list(struct stack_record *stack_record) +{ + unsigned long flags; + struct stack *stack; + + stack = kmalloc(sizeof(*stack), GFP_KERNEL); + if (stack) { + stack->stack_record = stack_record; + stack->next = NULL; + + spin_lock_irqsave(&stack_list_lock, flags); + if (!stack_list) { + stack_list = stack; + } else { + stack->next = stack_list; + stack_list = stack; + } + spin_unlock_irqrestore(&stack_list_lock, flags); + } +} + +static void inc_stack_record_count(depot_stack_handle_t handle) +{ + struct stack_record *stack_record = __stack_depot_get_stack_record(handle); + + if (stack_record) { + /* + * New stack_record's that do not use STACK_DEPOT_FLAG_GET start + * with REFCOUNT_SATURATED to catch spurious increments of their + * refcount. + * Since we do not use STACK_DEPOT_FLAG_{GET,PUT} API, let us + * set a refcount of 1 ourselves. + */ + if (refcount_read(&stack_record->count) == REFCOUNT_SATURATED) { + refcount_set(&stack_record->count, 1); + + /* Add the new stack_record to our list */ + add_stack_record_to_list(stack_record); + } + refcount_inc(&stack_record->count); + } +} + +static void dec_stack_record_count(depot_stack_handle_t handle) +{ + struct stack_record *stack_record = __stack_depot_get_stack_record(handle); + + if (stack_record) + refcount_dec(&stack_record->count); +} + static __always_inline depot_stack_handle_t create_dummy_stack(void) { unsigned long entries[4]; @@ -140,6 +199,7 @@ 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(); @@ -147,6 +207,9 @@ void __reset_page_owner(struct page *page, unsigned short order) if (unlikely(!page_ext)) return; + page_owner = get_page_owner(page_ext); + alloc_handle = page_owner->handle; + handle = save_stack(GFP_NOWAIT | __GFP_NOWARN); for (i = 0; i < (1 << order); i++) { __clear_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags); @@ -158,6 +221,15 @@ void __reset_page_owner(struct page *page, unsigned short order) page_ext = page_ext_next(page_ext); } page_ext_put(page_ext); + if (alloc_handle != early_handle) + /* + * early_handle is being set as a handle for all those + * early allocated pages. See init_pages_in_zone(). + * Since their refcount is not being incremented because + * the machinery is not ready yet, we cannot decrement + * their refcount either. + */ + dec_stack_record_count(alloc_handle); } static inline void __set_page_owner_handle(struct page_ext *page_ext, @@ -199,6 +271,7 @@ noinline void __set_page_owner(struct page *page, unsigned short order, return; __set_page_owner_handle(page_ext, handle, order, gfp_mask); page_ext_put(page_ext); + inc_stack_record_count(handle); } void __set_page_owner_migrate_reason(struct page *page, int reason) -- 2.43.0