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[2620:137:e000::1:20]) by mx.google.com with ESMTP id je11-20020a170903264b00b001a687bb33f5si18108124plb.434.2023.05.16.11.34.17; Tue, 16 May 2023 11:34:30 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@suse.de header.s=susede2_rsa header.b=u0cvZ0lZ; dkim=neutral (no key) header.i=@suse.de header.s=susede2_ed25519; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=suse.de Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230225AbjEPSZu (ORCPT + 99 others); Tue, 16 May 2023 14:25:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37880 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229536AbjEPSZt (ORCPT ); Tue, 16 May 2023 14:25:49 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 615BF26A6 for ; Tue, 16 May 2023 11:25:47 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 174571FE73; Tue, 16 May 2023 18:25:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1684261546; 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; bh=va2PlQ9fTKLDOkUDFaD7bMLHV5h0Zea9LBMRTULprJM=; b=u0cvZ0lZhnfnxdniqsZFP/a5To6ZmQX0JDsCr/jTuRDNYBFNngi8P+pCh/7j+UIM/qfDpj FgdzCNJWDdIOa2EsBDmg3tc/zk2J0dBMng1lU6+ON9Sfhw65xp5gSR7RT7NBSOfTOjjS32 u33gXNiGJ4hKqPVfd9mWL6qV7je29EI= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1684261546; 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; bh=va2PlQ9fTKLDOkUDFaD7bMLHV5h0Zea9LBMRTULprJM=; b=WOMgTTrwBGK1BhcJ4nzcOVvYv2mCDhG3/PvmyY/sWSpoqCc6SfOgxfUddsbANtaERHd6pR op4x7WMYct0oBUBQ== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 496A6138F5; Tue, 16 May 2023 18:25:45 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id s/E4DqnKY2TeVQAAMHmgww (envelope-from ); Tue, 16 May 2023 18:25:45 +0000 From: Oscar Salvador To: Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Michal Hocko , Vlastimil Babka , Waiman Long , Suren Baghdasaryan , Marco Elver , Andrey Konovalov , Eric Dumazet , Alexander Potapenko , Oscar Salvador Subject: [PATCH v5 0/3] page_owner: print stacks and their counter Date: Tue, 16 May 2023 20:25:34 +0200 Message-Id: <20230516182537.3139-1-osalvador@suse.de> X-Mailer: git-send-email 2.40.0 MIME-Version: 1.0 X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,SPF_HELO_NONE, SPF_PASS,T_SCC_BODY_TEXT_LINE,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1766060794174149832?= X-GMAIL-MSGID: =?utf-8?q?1766076785080240552?= Changes v4 -> v5: - Move page_owner_stack_threshold to page_owner file (suggested by Alexander Potapenko) - Make the stack refcount more generic, and do not assume it will be only used for page_owner (suggested by Alexander Potapenko) Changes v3 -> v4: - Rebase (long time has passed) - Use boolean instead of enum for action by Alexander Potapenko - (I left some feedback untouched because it's been long and would like to discuss it here now instead of re-vamping and old thread) Changes v2 -> v3: - Replace interface in favor of seq operations (suggested by Vlastimil) - Use debugfs interface to store/read valued (suggested by Ammar) Hi, page_owner is a great debug functionality tool that gets us to know about all pages that have been allocated/freed and their stacktrace. This comes very handy when e.g: debugging leaks, as with some scripting we might be able to see those stacktraces that are allocating pages but not freeing theme. In my experience, that is one of the most useful cases, but it can get really tedious to screen through all pages aand try to reconstruct the stack <-> allocated/freed relationship. There is a lot of noise to cancel off. This patch aims to fix that by adding a new functionality into page_owner. What this does is to create a new read-only file "page_owner_stacks", which prints only the allocating stacktraces and their counting, being that the times the stacktrace has allocated - the times it has freed. So we have a clear overview of stacks <-> allocated/freed relationship without the need to fiddle with pages and trying to match free stacktraces with allocated stacktraces. This is achieved by adding a new refcount_t field in the stack_record struct, incrementing that refcount_t everytime the same stacktrace allocates, and decrementing it when it frees a page. Details can be seen in the respective patches. We also create another file called "page_owner_threshold", which let us specify a threshold, so when when reading from "page_owner_stacks", we will only see those stacktraces which counting goes beyond the threshold we specified. One thing I am not completely happy about is to polute lib/stackdepot.c file with the stack_* functions. We could sort that out if the stack_record struct definitions were in a header file instead of stackdepot.c. But I am not sure about that trade-off, so suggestions are accepted. A PoC can be found below: # cat /sys/kernel/debug/page_owner_threshold 0 # cat /sys/kernel/debug/page_owner_stacks > stacks_full.txt # head -32 stacks_full.txt prep_new_page+0x10d/0x180 get_page_from_freelist+0x1bd6/0x1e10 __alloc_pages+0x194/0x360 alloc_page_interleave+0x13/0x90 new_slab+0x31d/0x530 ___slab_alloc+0x5d7/0x720 __slab_alloc.isra.85+0x4a/0x90 kmem_cache_alloc+0x455/0x4a0 acpi_ps_alloc_op+0x57/0x8f acpi_ps_create_scope_op+0x12/0x23 acpi_ps_execute_method+0x102/0x2c1 acpi_ns_evaluate+0x343/0x4da acpi_evaluate_object+0x1cb/0x392 acpi_run_osc+0x135/0x260 acpi_init+0x165/0x4ed do_one_initcall+0x3e/0x200 stack count: 2 free_pcp_prepare+0x287/0x5c0 free_unref_page+0x1c/0xd0 __mmdrop+0x50/0x160 finish_task_switch+0x249/0x2b0 __schedule+0x2c3/0x960 schedule+0x44/0xb0 futex_wait_queue+0x70/0xd0 futex_wait+0x160/0x250 do_futex+0x11c/0x1b0 __x64_sys_futex+0x5e/0x1d0 do_syscall_64+0x37/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd stack count: 1 # echo 10000 > /sys/kernel/debug/page_owner_threshold # cat /sys/kernel/debug/page_owner_stacks > stacks_10000.txt # cat stacks_10000.txt prep_new_page+0x10d/0x180 get_page_from_freelist+0x1bd6/0x1e10 __alloc_pages+0x194/0x360 folio_alloc+0x17/0x40 page_cache_ra_unbounded+0x96/0x170 filemap_get_pages+0x23d/0x5e0 filemap_read+0xbf/0x3a0 __kernel_read+0x136/0x2f0 kernel_read_file+0x197/0x2d0 kernel_read_file_from_fd+0x54/0x90 __do_sys_finit_module+0x89/0x120 do_syscall_64+0x37/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd stack count: 36195 prep_new_page+0x10d/0x180 get_page_from_freelist+0x1bd6/0x1e10 __alloc_pages+0x194/0x360 folio_alloc+0x17/0x40 page_cache_ra_unbounded+0x96/0x170 filemap_get_pages+0x23d/0x5e0 filemap_read+0xbf/0x3a0 new_sync_read+0x106/0x180 vfs_read+0x16f/0x190 ksys_read+0xa5/0xe0 do_syscall_64+0x37/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd stack count: 44484 prep_new_page+0x10d/0x180 get_page_from_freelist+0x1bd6/0x1e10 __alloc_pages+0x194/0x360 folio_alloc+0x17/0x40 page_cache_ra_unbounded+0x96/0x170 filemap_get_pages+0xdd/0x5e0 filemap_read+0xbf/0x3a0 new_sync_read+0x106/0x180 vfs_read+0x16f/0x190 ksys_read+0xa5/0xe0 do_syscall_64+0x37/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd stack count: 17874 Oscar Salvador (3): lib/stackdepot: Add a refcount field in stack_record mm, page_owner: Add page_owner_stacks file to print out only stacks and their counte mm,page_owner: Filter out stacks by a threshold counter include/linux/stackdepot.h | 8 +++ lib/stackdepot.c | 128 ++++++++++++++++++++++++++++++++++--- mm/page_owner.c | 54 ++++++++++++++++ 3 files changed, 180 insertions(+), 10 deletions(-)