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Thu, 15 Feb 2024 21:58:05 +0000 (UTC) Received: from dovecot-director2.suse.de ([10.150.64.162]) by imap2.dmz-prg2.suse.org with ESMTPSA id eFbCN+2IzmXPAQAAn2gu4w (envelope-from ); Thu, 15 Feb 2024 21:58:05 +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 v10 5/7] mm,page_owner: Display all stacks and their count Date: Thu, 15 Feb 2024 22:59:05 +0100 Message-ID: <20240215215907.20121-6-osalvador@suse.de> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240215215907.20121-1-osalvador@suse.de> References: <20240215215907.20121-1-osalvador@suse.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: E7119C0013 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: wm9xiz9c5c74fu3jubf3oudxc7dnzzx5 X-HE-Tag: 1708034287-845001 X-HE-Meta: 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 8QFgiKDu j9frt7CuThHo2woo3Pkfy4rQ0DubctJuHOprx 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: 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..e99fbf822dd6 100644 --- a/mm/page_owner.c +++ b/mm/page_owner.c @@ -171,7 +171,13 @@ static void add_stack_record_to_list(struct stack_record *stack_record, spin_lock_irqsave(&stack_list_lock, flags); stack->next = stack_list; - stack_list = 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); } @@ -805,8 +811,90 @@ static const struct file_operations proc_page_owner_operations = { .llseek = lseek_page_owner, }; +static void *stack_start(struct seq_file *m, loff_t *ppos) +{ + struct stack *stack; + + if (*ppos == -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 = smp_load_acquire(&stack_list); + } else { + stack = m->private; + stack = stack->next; + } + + m->private = stack; + + return stack; +} + +static void *stack_next(struct seq_file *m, void *v, loff_t *ppos) +{ + struct stack *stack = v; + + stack = stack->next; + *ppos = stack ? *ppos + 1 : -1UL; + m->private = stack; + + return stack; +} + +static int stack_print(struct seq_file *m, void *v) +{ + int i, stack_count; + struct stack *stack = v; + unsigned long *entries; + unsigned long nr_entries; + struct stack_record *stack_record = stack->stack_record; + + nr_entries = stack_record->size; + entries = stack_record->entries; + stack_count = refcount_read(&stack_record->count) - 1; + + if (!nr_entries || nr_entries < 0 || stack_count < 1) + return 0; + + for (i = 0; i < nr_entries; i++) + seq_printf(m, " %pS\n", (void *)entries[i]); + seq_printf(m, "stack_count: %d\n\n", stack_count); + + return 0; +} + +static void stack_stop(struct seq_file *m, void *v) +{ +} + +static const struct seq_operations page_owner_stack_op = { + .start = stack_start, + .next = stack_next, + .stop = stack_stop, + .show = 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 = { + .open = page_owner_stack_open, + .read = seq_read, + .llseek = seq_lseek, + .release = 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) debugfs_create_file("page_owner", 0400, NULL, NULL, &proc_page_owner_operations); + dir = debugfs_create_dir("page_owner_stacks", NULL); + debugfs_create_file("show_stacks", 0400, dir, NULL, + &page_owner_stack_operations); return 0; } -- 2.43.0