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Tue, 13 Feb 2024 14:25:26 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 8FDaJ9Z7y2UsKQAAD6G6ig (envelope-from ); Tue, 13 Feb 2024 14:25:26 +0000 Message-ID: Date: Tue, 13 Feb 2024 15:25:26 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8 3/5] mm,page_owner: Display all stacks and their count Content-Language: en-US To: Oscar Salvador , Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Michal Hocko , Marco Elver , Andrey Konovalov , Alexander Potapenko References: <20240212223029.30769-1-osalvador@suse.de> <20240212223029.30769-4-osalvador@suse.de> From: Vlastimil Babka In-Reply-To: <20240212223029.30769-4-osalvador@suse.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: hnmczuyh8ziygsez5zcpnceipugkes7e X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: A73DA140002 X-HE-Tag: 1707834328-155694 X-HE-Meta: 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 VSzN70a7 tuPifn+850jbyUcQ+UK4nNman9eFk/jllz5haqvkAxdXxBLW3+hUTYjvF/29ePo7u+ESHiqpt6Edo0jMZz6bCc6FUBgGgeBNPByWPnhE8a6Jxu5fd44N8KYovEoIguakeDPAZ74QUuYnTZMMLPR46u7DjP1XR6OczKpoWRU2tJV9unb8kQfH7i0twi69C9uQWaz1spDdsuZ2ygfDcJvG81kJQAIZYj8AsRQJZ6Ecn/up8kLVVuO1A6qd/zd4fH1VukUQZuh9iiIcO30hKQTzC2uhlsgMxnBXn8Nz2qqjmUzkCOIfD9mQtSijXFA== 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: On 2/12/24 23:30, Oscar Salvador wrote: > 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 ... > +static int stack_print(struct seq_file *m, void *v) > +{ > + char *buf; > + int ret = 0; > + struct stack *stack = v; > + struct stack_record *stack_record = stack->stack_record; > + > + if (!stack_record->size || stack_record->size < 0 || > + refcount_read(&stack_record->count) < 2) > + return 0; > + > + buf = kzalloc(PAGE_SIZE, GFP_KERNEL); > + > + ret += stack_trace_snprint(buf, PAGE_SIZE, stack_record->entries, > + stack_record->size, 0); > + if (!ret) > + goto out; > + > + scnprintf(buf + ret, PAGE_SIZE - ret, "stack_count: %d\n\n", > + refcount_read(&stack_record->count)); > + > + seq_printf(m, buf); > + seq_puts(m, "\n\n"); > +out: > + kfree(buf); Seems rather wasteful to do kzalloc/kfree so you can print into that buffer first and then print/copy it again using seq_printf. If you give up on using stack_trace_snprintf() it's not much harder to print the stack directly with a loop of seq_printf. See e.g. slab_debugfs_show(). > + > + return 0; > +} > +