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Wed, 14 Feb 2024 17:00:54 +0000 (UTC) Received: from dovecot-director2.suse.de ([10.150.64.162]) by imap2.dmz-prg2.suse.org with ESMTPSA id yAQrCMbxzGUfMwAAn2gu4w (envelope-from ); Wed, 14 Feb 2024 17:00:54 +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 v9 1/7] lib/stackdepot: Fix first entry having a 0-handle Date: Wed, 14 Feb 2024 18:01:51 +0100 Message-ID: <20240214170157.17530-2-osalvador@suse.de> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240214170157.17530-1-osalvador@suse.de> References: <20240214170157.17530-1-osalvador@suse.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Authentication-Results: smtp-out1.suse.de; none X-Spamd-Result: default: False [1.90 / 50.00]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; R_MISSING_CHARSET(2.50)[]; MIME_GOOD(-0.10)[text/plain]; TO_MATCH_ENVRCPT_ALL(0.00)[]; BROKEN_CONTENT_TYPE(1.50)[]; RCVD_COUNT_THREE(0.00)[3]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; RCPT_COUNT_SEVEN(0.00)[9]; MID_CONTAINS_FROM(1.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; FREEMAIL_CC(0.00)[vger.kernel.org,kvack.org,suse.com,suse.cz,google.com,gmail.com,suse.de]; RCVD_TLS_ALL(0.00)[]; BAYES_HAM(-3.00)[100.00%] X-Spam-Level: * X-Spam-Score: 1.90 X-Spam-Flag: NO Content-Type: text/plain; charset="utf-8" The very first entry of stack_record gets a handle of 0, but this is wrong because stackdepot treats a 0-handle as a non-valid one. E.g: See the check in stack_depot_fetch() Fix this by adding and offset of 1. This bug has been lurking since the very beginning of stackdepot, but no one really cared as it seems. Because of that I am not adding a Fixes tag. Co-developed-by: Marco Elver Signed-off-by: Marco Elver Signed-off-by: Oscar Salvador Acked-by: Vlastimil Babka --- lib/stackdepot.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/lib/stackdepot.c b/lib/stackdepot.c index 4a7055a63d9f..c043a4186bc5 100644 --- a/lib/stackdepot.c +++ b/lib/stackdepot.c @@ -45,15 +45,16 @@ #define DEPOT_POOL_INDEX_BITS (DEPOT_HANDLE_BITS - DEPOT_OFFSET_BITS - \ STACK_DEPOT_EXTRA_BITS) #define DEPOT_POOLS_CAP 8192 +/* The pool_index is offset by 1 so the first record does not have a 0 han= dle. */ #define DEPOT_MAX_POOLS \ - (((1LL << (DEPOT_POOL_INDEX_BITS)) < DEPOT_POOLS_CAP) ? \ - (1LL << (DEPOT_POOL_INDEX_BITS)) : DEPOT_POOLS_CAP) + (((1LL << (DEPOT_POOL_INDEX_BITS)) - 1 < DEPOT_POOLS_CAP) ? \ + (1LL << (DEPOT_POOL_INDEX_BITS)) - 1 : DEPOT_POOLS_CAP) =20 /* Compact structure that stores a reference to a stack. */ union handle_parts { depot_stack_handle_t handle; struct { - u32 pool_index : DEPOT_POOL_INDEX_BITS; + u32 pool_index : DEPOT_POOL_INDEX_BITS; /* pool_index is offset by 1 */ u32 offset : DEPOT_OFFSET_BITS; u32 extra : STACK_DEPOT_EXTRA_BITS; }; @@ -372,7 +373,7 @@ static struct stack_record *depot_pop_free_pool(void **= prealloc, size_t size) stack =3D current_pool + pool_offset; =20 /* Pre-initialize handle once. */ - stack->handle.pool_index =3D pool_index; + stack->handle.pool_index =3D pool_index + 1; stack->handle.offset =3D pool_offset >> DEPOT_STACK_ALIGN; stack->handle.extra =3D 0; INIT_LIST_HEAD(&stack->hash_list); @@ -483,18 +484,19 @@ static struct stack_record *depot_fetch_stack(depot_s= tack_handle_t handle) const int pools_num_cached =3D READ_ONCE(pools_num); union handle_parts parts =3D { .handle =3D handle }; void *pool; + u32 pool_index =3D parts.pool_index - 1; size_t offset =3D parts.offset << DEPOT_STACK_ALIGN; struct stack_record *stack; =20 lockdep_assert_not_held(&pool_lock); =20 - if (parts.pool_index > pools_num_cached) { + if (pool_index > pools_num_cached) { WARN(1, "pool index %d out of bounds (%d) for stack id %08x\n", - parts.pool_index, pools_num_cached, handle); 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t=1707930055; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=JA43trKKhKihZJJ9usT00f7GursSmzhg3mriwKaV7y0=; b=Rz4F4l7Ovo8/4T70d83JG746eAdiF4zCQn1/+xsngvnA4gjUJscgUE9SwdzJkhV1NKc5g1 cpp19ge4u6YiZAAA== Received: from imap2.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap2.dmz-prg2.suse.org (Postfix) with ESMTPS id 62E1D13A0B; Wed, 14 Feb 2024 17:00:55 +0000 (UTC) Received: from dovecot-director2.suse.de ([10.150.64.162]) by imap2.dmz-prg2.suse.org with ESMTPSA id UKuAFcfxzGUfMwAAn2gu4w (envelope-from ); Wed, 14 Feb 2024 17:00:55 +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 v9 2/7] lib/stackdepot: Move stack_record struct definition into the header Date: Wed, 14 Feb 2024 18:01:52 +0100 Message-ID: <20240214170157.17530-3-osalvador@suse.de> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240214170157.17530-1-osalvador@suse.de> References: <20240214170157.17530-1-osalvador@suse.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Authentication-Results: smtp-out1.suse.de; none X-Spamd-Result: default: False [1.90 / 50.00]; RCVD_VIA_SMTP_AUTH(0.00)[]; TO_DN_SOME(0.00)[]; R_MISSING_CHARSET(2.50)[]; BROKEN_CONTENT_TYPE(1.50)[]; RCVD_COUNT_THREE(0.00)[3]; RCPT_COUNT_SEVEN(0.00)[9]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; BAYES_HAM(-3.00)[100.00%]; ARC_NA(0.00)[]; FROM_HAS_DN(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; TO_MATCH_ENVRCPT_ALL(0.00)[]; MIME_GOOD(-0.10)[text/plain]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; MID_CONTAINS_FROM(1.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email]; FUZZY_BLOCKED(0.00)[rspamd.com]; FREEMAIL_CC(0.00)[vger.kernel.org,kvack.org,suse.com,suse.cz,google.com,gmail.com,suse.de]; RCVD_TLS_ALL(0.00)[] X-Spam-Level: * X-Spam-Score: 1.90 X-Spam-Flag: NO Content-Type: text/plain; charset="utf-8" In order to move the heavy lifting into page_owner code, this one needs to have access to the stack_record structure, which right now sits in lib/stackdepot.c. Move it to the stackdepot.h header so page_owner can access stack_record's struct fields. Signed-off-by: Oscar Salvador Reviewed-by: Marco Elver Reviewed-by: Vlastimil Babka --- include/linux/stackdepot.h | 47 ++++++++++++++++++++++++++++++++++++++ lib/stackdepot.c | 45 +----------------------------------- 2 files changed, 48 insertions(+), 44 deletions(-) diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h index adcbb8f23600..c4b5ad57c066 100644 --- a/include/linux/stackdepot.h +++ b/include/linux/stackdepot.h @@ -30,6 +30,53 @@ typedef u32 depot_stack_handle_t; */ #define STACK_DEPOT_EXTRA_BITS 5 =20 +#define DEPOT_HANDLE_BITS (sizeof(depot_stack_handle_t) * 8) + +#define DEPOT_POOL_ORDER 2 /* Pool size order, 4 pages */ +#define DEPOT_POOL_SIZE (1LL << (PAGE_SHIFT + DEPOT_POOL_ORDER)) +#define DEPOT_STACK_ALIGN 4 +#define DEPOT_OFFSET_BITS (DEPOT_POOL_ORDER + PAGE_SHIFT - DEPOT_STACK_ALI= GN) +#define DEPOT_POOL_INDEX_BITS (DEPOT_HANDLE_BITS - DEPOT_OFFSET_BITS - \ + STACK_DEPOT_EXTRA_BITS) + +#ifdef CONFIG_STACKDEPOT +/* Compact structure that stores a reference to a stack. */ +union handle_parts { + depot_stack_handle_t handle; + struct { + /* pool_index is offset by 1 */ + u32 pool_index : DEPOT_POOL_INDEX_BITS; + u32 offset : DEPOT_OFFSET_BITS; + u32 extra : STACK_DEPOT_EXTRA_BITS; + }; +}; + +struct stack_record { + struct list_head hash_list; /* Links in the hash table */ + u32 hash; /* Hash in hash table */ + u32 size; /* Number of stored frames */ + union handle_parts handle; /* Constant after initialization */ + refcount_t count; + union { + unsigned long entries[CONFIG_STACKDEPOT_MAX_FRAMES]; /* Frames */ + struct { + /* + * An important invariant of the implementation is to + * only place a stack record onto the freelist iff its + * refcount is zero. Because stack records with a zero + * refcount are never considered as valid, it is safe to + * union @entries and freelist management state below. + * Conversely, as soon as an entry is off the freelist + * and its refcount becomes non-zero, the below must not + * be accessed until being placed back on the freelist. + */ + struct list_head free_list; /* Links in the freelist */ + unsigned long rcu_state; /* RCU cookie */ + }; + }; +}; +#endif + typedef u32 depot_flags_t; =20 /* diff --git a/lib/stackdepot.c b/lib/stackdepot.c index c043a4186bc5..4a661a6777da 100644 --- a/lib/stackdepot.c +++ b/lib/stackdepot.c @@ -36,55 +36,12 @@ #include #include =20 -#define DEPOT_HANDLE_BITS (sizeof(depot_stack_handle_t) * 8) - -#define DEPOT_POOL_ORDER 2 /* Pool size order, 4 pages */ -#define DEPOT_POOL_SIZE (1LL << (PAGE_SHIFT + DEPOT_POOL_ORDER)) -#define DEPOT_STACK_ALIGN 4 -#define DEPOT_OFFSET_BITS (DEPOT_POOL_ORDER + PAGE_SHIFT - DEPOT_STACK_ALI= GN) -#define DEPOT_POOL_INDEX_BITS (DEPOT_HANDLE_BITS - DEPOT_OFFSET_BITS - \ - STACK_DEPOT_EXTRA_BITS) #define DEPOT_POOLS_CAP 8192 -/* The pool_index is offset by 1 so the first record does not have a 0 han= dle. */ +/* The pool_index is offset by 1 so the first record does not have a 0 han= dle */ #define DEPOT_MAX_POOLS \ (((1LL << (DEPOT_POOL_INDEX_BITS)) - 1 < DEPOT_POOLS_CAP) ? \ (1LL << (DEPOT_POOL_INDEX_BITS)) - 1 : DEPOT_POOLS_CAP) =20 -/* Compact structure that stores a reference to a stack. */ -union handle_parts { - depot_stack_handle_t handle; - struct { - u32 pool_index : DEPOT_POOL_INDEX_BITS; /* pool_index is offset by 1 */ - u32 offset : DEPOT_OFFSET_BITS; - u32 extra : STACK_DEPOT_EXTRA_BITS; - }; -}; - -struct stack_record { - struct list_head hash_list; /* Links in the hash table */ - u32 hash; /* Hash in hash table */ - u32 size; /* Number of stored frames */ - union handle_parts handle; /* Constant after initialization */ - refcount_t count; - union { - unsigned long entries[CONFIG_STACKDEPOT_MAX_FRAMES]; /* Frames */ - struct { - /* - * An important invariant of the implementation is to - * only place a stack record onto the freelist iff its - * refcount is zero. 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charset="utf-8" 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, 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. For now, add to stack_list only the stack_records of dummy_handle and failure_handle, and set their refcount of 1. Further patches will add code to increment or decrement stack_records count on allocation and free operation. Signed-off-by: Oscar Salvador Reviewed-by: Marco Elver Reviewed-by: Vlastimil Babka --- include/linux/stackdepot.h | 11 +++++++++++ lib/stackdepot.c | 8 ++++++++ mm/page_owner.c | 15 +++++++++++++++ 3 files changed, 34 insertions(+) diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h index c4b5ad57c066..3c6caa5abc7c 100644 --- a/include/linux/stackdepot.h +++ b/include/linux/stackdepot.h @@ -178,6 +178,17 @@ depot_stack_handle_t stack_depot_save_flags(unsigned l= ong *entries, depot_stack_handle_t stack_depot_save(unsigned long *entries, unsigned int nr_entries, gfp_t gfp_flags); =20 +/** + * __stack_depot_get_stack_record - Get a pointer to a stack_record struct + * + * @handle: Stack depot handle + * + * This function is only for internal purposes. + * + * Return: Returns a pointer to a stack_record struct + */ +struct stack_record *__stack_depot_get_stack_record(depot_stack_handle_t h= andle); + /** * stack_depot_fetch - Fetch a stack trace from stack depot * diff --git a/lib/stackdepot.c b/lib/stackdepot.c index 4a661a6777da..3da6d7cfcdfb 100644 --- a/lib/stackdepot.c +++ b/lib/stackdepot.c @@ -687,6 +687,14 @@ depot_stack_handle_t stack_depot_save(unsigned long *e= ntries, } EXPORT_SYMBOL_GPL(stack_depot_save); =20 +struct stack_record *__stack_depot_get_stack_record(depot_stack_handle_t h= andle) +{ + 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..33e342b15d9b 100644 --- a/mm/page_owner.c +++ b/mm/page_owner.c @@ -36,6 +36,14 @@ struct page_owner { pid_t free_tgid; }; =20 +struct stack { + struct stack_record *stack_record; + struct stack *next; +}; +static struct stack dummy_stack; +static struct stack failure_stack; +static struct stack *stack_list; + static bool page_owner_enabled __initdata; DEFINE_STATIC_KEY_FALSE(page_owner_inited); =20 @@ -95,6 +103,13 @@ static __init void init_page_owner(void) register_early_stack(); static_branch_enable(&page_owner_inited); init_early_allocated_pages(); + /* Initialize dummy and failure stacks and link them to stack_list */ + dummy_stack.stack_record =3D __stack_depot_get_stack_record(dummy_handle); 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none X-Spamd-Result: default: False [1.90 / 50.00]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; R_MISSING_CHARSET(2.50)[]; MIME_GOOD(-0.10)[text/plain]; TO_MATCH_ENVRCPT_ALL(0.00)[]; BROKEN_CONTENT_TYPE(1.50)[]; RCVD_COUNT_THREE(0.00)[3]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; RCPT_COUNT_SEVEN(0.00)[9]; MID_CONTAINS_FROM(1.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; FREEMAIL_CC(0.00)[vger.kernel.org,kvack.org,suse.com,suse.cz,google.com,gmail.com,suse.de]; RCVD_TLS_ALL(0.00)[]; BAYES_HAM(-3.00)[100.00%] X-Spam-Level: * X-Spam-Score: 1.90 X-Spam-Flag: NO Content-Type: text/plain; charset="utf-8" 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). Newly allocated stack_record structs will be added to the list stack_list via add_stack_record_to_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 Reviewed-by: Marco Elver Reviewed-by: Vlastimil Babka --- mm/page_owner.c | 73 ++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 72 insertions(+), 1 deletion(-) diff --git a/mm/page_owner.c b/mm/page_owner.c index 33e342b15d9b..df6a923af5de 100644 --- a/mm/page_owner.c +++ b/mm/page_owner.c @@ -43,6 +43,7 @@ struct stack { static struct stack dummy_stack; static struct stack failure_stack; static struct stack *stack_list; +static DEFINE_SPINLOCK(stack_list_lock); =20 static bool page_owner_enabled __initdata; DEFINE_STATIC_KEY_FALSE(page_owner_inited); @@ -150,11 +151,68 @@ static noinline depot_stack_handle_t save_stack(gfp_t= flags) return handle; } =20 +static void add_stack_record_to_list(struct stack_record *stack_record, + gfp_t gfp_mask) +{ + unsigned long flags; + struct stack *stack; + + /* Filter gfp_mask the same way stackdepot does, for consistency */ + gfp_mask &=3D ~GFP_ZONEMASK; + gfp_mask &=3D (GFP_ATOMIC | GFP_KERNEL); + gfp_mask |=3D __GFP_NOWARN; + + stack =3D kmalloc(sizeof(*stack), gfp_mask); + if (!stack) + return; + + stack->stack_record =3D stack_record; + stack->next =3D NULL; + + spin_lock_irqsave(&stack_list_lock, flags); + stack->next =3D stack_list; + stack_list =3D stack; + spin_unlock_irqrestore(&stack_list_lock, flags); +} + +static void inc_stack_record_count(depot_stack_handle_t handle, gfp_t gfp_= mask) +{ + struct stack_record *stack_record =3D __stack_depot_get_stack_record(hand= le); + + if (!stack_record) + return; + + /* + * 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 API, let us + * set a refcount of 1 ourselves. + */ + if (refcount_read(&stack_record->count) =3D=3D REFCOUNT_SATURATED) { + int old =3D REFCOUNT_SATURATED; + + if (atomic_try_cmpxchg_relaxed(&stack_record->count.refs, &old, 1)) + /* Add the new stack_record to our list */ + add_stack_record_to_list(stack_record, gfp_mask); + } + refcount_inc(&stack_record->count); +} + +static void dec_stack_record_count(depot_stack_handle_t handle) +{ + struct stack_record *stack_record =3D __stack_depot_get_stack_record(hand= le); + + if (stack_record) + refcount_dec(&stack_record->count); +} + 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 =3D local_clock(); =20 @@ -162,17 +220,29 @@ void __reset_page_owner(struct page *page, unsigned s= hort order) if (unlikely(!page_ext)) return; =20 + page_owner =3D get_page_owner(page_ext); + alloc_handle =3D page_owner->handle; + handle =3D save_stack(GFP_NOWAIT | __GFP_NOWARN); for (i =3D 0; i < (1 << order); i++) { __clear_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags); - page_owner =3D get_page_owner(page_ext); page_owner->free_handle =3D handle; page_owner->free_ts_nsec =3D free_ts_nsec; page_owner->free_pid =3D current->pid; page_owner->free_tgid =3D current->tgid; page_ext =3D page_ext_next(page_ext); + page_owner =3D get_page_owner(page_ext); } page_ext_put(page_ext); + if (alloc_handle !=3D 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); } =20 static inline void __set_page_owner_handle(struct page_ext *page_ext, @@ -214,6 +284,7 @@ noinline void __set_page_owner(struct page *page, unsig= ned short order, return; __set_page_owner_handle(page_ext, handle, order, gfp_mask); page_ext_put(page_ext); + inc_stack_record_count(handle, gfp_mask); } =20 void __set_page_owner_migrate_reason(struct page *page, int reason) --=20 2.43.0 From nobody Sun Feb 8 03:27:30 2026 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.223.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B12E060DE7 for ; Wed, 14 Feb 2024 17:01:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=195.135.223.131 ARC-Seal: i=1; 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Wed, 14 Feb 2024 17:00:58 +0000 (UTC) Received: from dovecot-director2.suse.de ([10.150.64.162]) by imap2.dmz-prg2.suse.org with ESMTPSA id gMbiHMrxzGUfMwAAn2gu4w (envelope-from ); Wed, 14 Feb 2024 17:00:58 +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 v9 5/7] mm,page_owner: Display all stacks and their count Date: Wed, 14 Feb 2024 18:01:55 +0100 Message-ID: <20240214170157.17530-6-osalvador@suse.de> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240214170157.17530-1-osalvador@suse.de> References: <20240214170157.17530-1-osalvador@suse.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Authentication-Results: smtp-out2.suse.de; none X-Spamd-Result: default: False [1.90 / 50.00]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; R_MISSING_CHARSET(2.50)[]; MIME_GOOD(-0.10)[text/plain]; TO_MATCH_ENVRCPT_ALL(0.00)[]; BROKEN_CONTENT_TYPE(1.50)[]; RCVD_COUNT_THREE(0.00)[3]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; RCPT_COUNT_SEVEN(0.00)[9]; MID_CONTAINS_FROM(1.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; FREEMAIL_CC(0.00)[vger.kernel.org,kvack.org,suse.com,suse.cz,google.com,gmail.com,suse.de]; RCVD_TLS_ALL(0.00)[]; BAYES_HAM(-3.00)[100.00%] X-Spam-Level: * X-Spam-Score: 1.90 X-Spam-Flag: NO Content-Type: text/plain; charset="utf-8" This patch adds a new directory called 'page_owner_stacks' under /sys/kernel/debug/, with a file called 'show_stacks' in it. Reading from that file will show all stacks that were added by page_owner followed by their counting, giving us a clear overview of stack <-> count relationship. E.g: prep_new_page+0xa9/0x120 get_page_from_freelist+0x801/0x2210 __alloc_pages+0x18b/0x350 alloc_pages_mpol+0x91/0x1f0 folio_alloc+0x14/0x50 filemap_alloc_folio+0xb2/0x100 __filemap_get_folio+0x14a/0x490 ext4_write_begin+0xbd/0x4b0 [ext4] generic_perform_write+0xc1/0x1e0 ext4_buffered_write_iter+0x68/0xe0 [ext4] ext4_file_write_iter+0x70/0x740 [ext4] vfs_write+0x33d/0x420 ksys_write+0xa5/0xe0 do_syscall_64+0x80/0x160 entry_SYSCALL_64_after_hwframe+0x6e/0x76 stack_count: 4578 The seq stack_{start,next} functions will iterate through the list stack_list in order to print all stacks. Signed-off-by: Oscar Salvador Acked-by: Marco Elver Reviewed-by: Vlastimil Babka --- mm/page_owner.c | 93 ++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 92 insertions(+), 1 deletion(-) diff --git a/mm/page_owner.c b/mm/page_owner.c index df6a923af5de..5258a417f4d1 100644 --- a/mm/page_owner.c +++ b/mm/page_owner.c @@ -171,7 +171,13 @@ static void add_stack_record_to_list(struct stack_reco= rd *stack_record, =20 spin_lock_irqsave(&stack_list_lock, flags); stack->next =3D stack_list; - stack_list =3D stack; + /* + * This pairs with smp_load_acquire() from function + * stack_start(). This guarantees that stack_start() + * will see an updated stack_list before starting to + * traverse the list. + */ + smp_store_release(&stack_list, stack); spin_unlock_irqrestore(&stack_list_lock, flags); } =20 @@ -805,8 +811,90 @@ static const struct file_operations proc_page_owner_op= erations =3D { .llseek =3D lseek_page_owner, }; =20 +static void *stack_start(struct seq_file *m, loff_t *ppos) +{ + struct stack *stack; + + if (*ppos =3D=3D -1UL) + return NULL; + + if (!*ppos) { + /* + * This pairs with smp_store_release() from function + * add_stack_record_to_list(), so we get a consistent + * value of stack_list. + */ + stack =3D smp_load_acquire(&stack_list); + } else { + stack =3D m->private; + stack =3D stack->next; + } + + m->private =3D stack; + + return stack; +} + +static void *stack_next(struct seq_file *m, void *v, loff_t *ppos) +{ + struct stack *stack =3D v; + + stack =3D stack->next; + *ppos =3D stack ? *ppos + 1 : -1UL; + m->private =3D stack; + + return stack; +} + +static int stack_print(struct seq_file *m, void *v) +{ + int i; + struct stack *stack =3D v; + unsigned long *entries; + unsigned long nr_entries; + struct stack_record *stack_record =3D stack->stack_record; + + nr_entries =3D stack_record->size; + entries =3D stack_record->entries; + + if (!nr_entries || nr_entries < 0 || + refcount_read(&stack_record->count) < 2) + return 0; + + for (i =3D 0; i < nr_entries; i++) + seq_printf(m, " %pS\n", (void *)entries[i]); + seq_printf(m, "stack_count: %d\n\n", refcount_read(&stack_record->count)); + + return 0; +} + +static void stack_stop(struct seq_file *m, void *v) +{ +} + +static const struct seq_operations page_owner_stack_op =3D { + .start =3D stack_start, + .next =3D stack_next, + .stop =3D stack_stop, + .show =3D stack_print +}; + +static int page_owner_stack_open(struct inode *inode, struct file *file) +{ + return seq_open_private(file, &page_owner_stack_op, 0); +} + +static const struct file_operations page_owner_stack_operations =3D { + .open =3D page_owner_stack_open, + .read =3D seq_read, + .llseek =3D seq_lseek, + .release =3D seq_release, +}; + static int __init pageowner_init(void) { + struct dentry *dir; + if (!static_branch_unlikely(&page_owner_inited)) { pr_info("page_owner is disabled\n"); return 0; @@ -814,6 +902,9 @@ static int __init pageowner_init(void) =20 debugfs_create_file("page_owner", 0400, NULL, NULL, &proc_page_owner_operations); + dir =3D debugfs_create_dir("page_owner_stacks", NULL); + debugfs_create_file("show_stacks", 0400, dir, NULL, + &page_owner_stack_operations); =20 return 0; } --=20 2.43.0 From nobody Sun Feb 8 03:27:30 2026 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.223.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B93A260EC9 for ; Wed, 14 Feb 2024 17:01:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=195.135.223.131 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707930064; cv=none; b=qooR67bEb4q6Y46+LIWlBvbZMWejM/D+Xtp219zRIDd7tbQCwsmvRDpIuboN7tAiY+DVuPjbKF2T5yqV7jwW7bjK8ukA4S60IDucflEgXp3BunB3phlHoR3+4ZEzE8FW/O2k9AfEYG4BRBwigoLZhxlBsuzTZcqJYbsLrV67k0Y= ARC-Message-Signature: i=1; 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none X-Spamd-Result: default: False [3.36 / 50.00]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; R_MISSING_CHARSET(2.50)[]; MIME_GOOD(-0.10)[text/plain]; TO_MATCH_ENVRCPT_ALL(0.00)[]; BROKEN_CONTENT_TYPE(1.50)[]; RCVD_COUNT_THREE(0.00)[3]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; RCPT_COUNT_SEVEN(0.00)[9]; MID_CONTAINS_FROM(1.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; FREEMAIL_CC(0.00)[vger.kernel.org,kvack.org,suse.com,suse.cz,google.com,gmail.com,suse.de]; RCVD_TLS_ALL(0.00)[]; BAYES_HAM(-1.54)[91.97%] X-Spam-Level: *** X-Spam-Score: 3.36 X-Spam-Flag: NO Content-Type: text/plain; charset="utf-8" We want to be able to filter out the stacks based on a threshold we can can tune. By writing to 'count_threshold' file, we can adjust the threshold value. Signed-off-by: Oscar Salvador Reviewed-by: Vlastimil Babka --- mm/page_owner.c | 29 +++++++++++++++++++++++++---- 1 file changed, 25 insertions(+), 4 deletions(-) diff --git a/mm/page_owner.c b/mm/page_owner.c index 5258a417f4d1..9b975f59b773 100644 --- a/mm/page_owner.c +++ b/mm/page_owner.c @@ -846,9 +846,11 @@ static void *stack_next(struct seq_file *m, void *v, l= off_t *ppos) return stack; } =20 +static unsigned long page_owner_stack_threshold; + static int stack_print(struct seq_file *m, void *v) { - int i; + int i, stack_count; struct stack *stack =3D v; unsigned long *entries; unsigned long nr_entries; @@ -856,14 +858,15 @@ static int stack_print(struct seq_file *m, void *v) =20 nr_entries =3D stack_record->size; entries =3D stack_record->entries; + stack_count =3D refcount_read(&stack_record->count); =20 - if (!nr_entries || nr_entries < 0 || - refcount_read(&stack_record->count) < 2) + if (!nr_entries || nr_entries < 0 || stack_count < 2 || + stack_count < page_owner_stack_threshold) return 0; =20 for (i =3D 0; i < nr_entries; i++) seq_printf(m, " %pS\n", (void *)entries[i]); - seq_printf(m, "stack_count: %d\n\n", refcount_read(&stack_record->count)); + seq_printf(m, "stack_count: %d\n\n", stack_count); =20 return 0; } @@ -891,6 +894,22 @@ static const struct file_operations page_owner_stack_o= perations =3D { .release =3D seq_release, }; =20 +static int page_owner_threshold_get(void *data, u64 *val) +{ + *val =3D READ_ONCE(page_owner_stack_threshold); + return 0; +} + +static int page_owner_threshold_set(void *data, u64 val) +{ + WRITE_ONCE(page_owner_stack_threshold, val); + return 0; +} + +DEFINE_SIMPLE_ATTRIBUTE(proc_page_owner_threshold, &page_owner_threshold_g= et, + &page_owner_threshold_set, "%llu"); + + static int __init pageowner_init(void) { struct dentry *dir; @@ -905,6 +924,8 @@ static int __init pageowner_init(void) dir =3D debugfs_create_dir("page_owner_stacks", NULL); debugfs_create_file("show_stacks", 0400, dir, NULL, &page_owner_stack_operations); + debugfs_create_file("count_threshold", 0600, dir, NULL, + &proc_page_owner_threshold); 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RCVD_TLS_ALL(0.00)[] X-Spam-Score: -0.82 X-Rspamd-Queue-Id: 03EC121CF4 X-Spam-Flag: NO Content-Type: text/plain; charset="utf-8" Update page_owner documentation including the new page_owner_stacks feature to show how it can be used. Signed-off-by: Oscar Salvador Reviewed-by: Marco Elver Reviewed-by: Vlastimil Babka --- Documentation/mm/page_owner.rst | 45 +++++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+) diff --git a/Documentation/mm/page_owner.rst b/Documentation/mm/page_owner.= rst index 62e3f7ab23cc..0d0334cd5179 100644 --- a/Documentation/mm/page_owner.rst +++ b/Documentation/mm/page_owner.rst @@ -24,6 +24,11 @@ fragmentation statistics can be obtained through gfp fla= g information of each page. It is already implemented and activated if page owner is enabled. Other usages are more than welcome. =20 +It can also be used to show all the stacks and their outstanding +allocations, which gives us a quick overview of where the memory is going +without the need to screen through all the pages and match the allocation +and free operation. + page owner is disabled by default. So, if you'd like to use it, you need to add "page_owner=3Don" to your boot cmdline. If the kernel is built with page owner and page owner is disabled in runtime due to not enabling @@ -68,6 +73,46 @@ Usage =20 4) Analyze information from page owner:: =20 + cat /sys/kernel/debug/page_owner_stacks/show_stacks > stacks.txt + cat stacks.txt + prep_new_page+0xa9/0x120 + get_page_from_freelist+0x7e6/0x2140 + __alloc_pages+0x18a/0x370 + new_slab+0xc8/0x580 + ___slab_alloc+0x1f2/0xaf0 + __slab_alloc.isra.86+0x22/0x40 + kmem_cache_alloc+0x31b/0x350 + __khugepaged_enter+0x39/0x100 + dup_mmap+0x1c7/0x5ce + copy_process+0x1afe/0x1c90 + kernel_clone+0x9a/0x3c0 + __do_sys_clone+0x66/0x90 + do_syscall_64+0x7f/0x160 + entry_SYSCALL_64_after_hwframe+0x6c/0x74 + stack_count: 234 + ... + ... + echo 7000 > /sys/kernel/debug/page_owner_stacks/count_threshold + cat /sys/kernel/debug/page_owner_stacks/show_stacks> stacks_7000.txt + cat stacks_7000.txt + prep_new_page+0xa9/0x120 + get_page_from_freelist+0x7e6/0x2140 + __alloc_pages+0x18a/0x370 + alloc_pages_mpol+0xdf/0x1e0 + folio_alloc+0x14/0x50 + filemap_alloc_folio+0xb0/0x100 + page_cache_ra_unbounded+0x97/0x180 + filemap_fault+0x4b4/0x1200 + __do_fault+0x2d/0x110 + do_pte_missing+0x4b0/0xa30 + __handle_mm_fault+0x7fa/0xb70 + handle_mm_fault+0x125/0x300 + do_user_addr_fault+0x3c9/0x840 + exc_page_fault+0x68/0x150 + asm_exc_page_fault+0x22/0x30 + stack_count: 8248 + ... + cat /sys/kernel/debug/page_owner > page_owner_full.txt ./page_owner_sort page_owner_full.txt sorted_page_owner.txt =20 --=20 2.43.0