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bh=5mDRvhwnMwgzeijqb31DW7JsO5NS0pT9KG3gT407n+Y=; b=RJ7e5vX6E2mR/bP7JxfH8ysa1673SdJoh94Nsu3neEyRTbQH8tsYgTc8XCQ0ZyrV6lrvum Zxwg3aUvFYU8lHCQ== Received: from imap1.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 imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id B3EAC13984; Thu, 8 Feb 2024 23:45:07 +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 BhSfKINnxWWUfAAAD6G6ig (envelope-from ); Thu, 08 Feb 2024 23:45:07 +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 v7 0/4] page_owner: print stacks and their outstanding allocations Date: Fri, 9 Feb 2024 00:45:35 +0100 Message-ID: <20240208234539.19113-1-osalvador@suse.de> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 X-Spamd-Bar: + X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 58CBE1A0005 X-Stat-Signature: cqhs6urw3mo4kphmjqiyt6snafuwk75c X-Rspam-User: X-HE-Tag: 1707435910-251727 X-HE-Meta: U2FsdGVkX19T7g7pB92nHKvIeqmyHCfZNMQvvBq6beY+yjFf9M7V5JZjheh78jeK5lq0pwDkUDrvAHrMREAnYam2zbaByBBSuMDAy8LL5FrREi4v7RAnO5SL14l/i4t2u2Yz/GfXZKWaHrer+jaTopA0Z4aLnWw9Pezr6zP0cUSayCkEowBpfa/FfE8R9XEwJNgj9aLegeaub73FDe+AlMj5odUL97Dh737Y3yZIn19B/KrNyyiLuWecg9q5E0DSEJeI2O+TZvUxoWC5fIgYnlDvH9je5pDQmyrIC1p2BO7zTqThDmiGRfbNspRUQKI/aAIOKzzEVaTpiB47/F5VGeEq/NX38EnhC/mP2FtTiFx8afiXgeOUpoROcBHBMgQrHqsEo60O2wm9k1pX4rWuW4JXWIoczAoGBOOM1yndxhgl3ye/oNvdQMjxei2Mn0OnfsPmXRwqCqRfWCEVtMRomwgQFBKNXR61bzcjc0uPwTlkPmHLrGHpDTRRxClH3BskR2xHmkda1ftVl6kTRLVE5/dJy/aHJ5bG6ezBP46mStj6wbIe9FCKjZ7qIdemn6wl23n5RGP8JE7yBc7P6xnxX/Jfe3uOPYooHcC8QSZ+A3oX8h4LYcYjznV+tkRHUoBi+syoZAPAHbH0t+OjfD9YUC0zPYrJkLeVRJ/JMLcrDSmt9VwYZ5MT2rD4jyKJHdSCCsVK/XaGlcofhiHLYMSBxJ9Gzxl07JHR/bPmnPh9aMukH46Gh3130z3Ax+Ix6Up+/4/d3MbQ9pC4k8aVGPJNGw654RY3bMV8E1Ixs2D4d5lemVAP9jPY/V76Of2pVL5cgUUD9cF0C1g4EZuX02bP7bpSgw+C2IcXHHmzkyxbCSj7dzkDj3vP3sy/LjRk94u3VOr44FAaWjPNyOEiZwEsANolPWEsPF3Yi5ZVYWMCuEm5aop3mgO0M5YbNhZToayOn5wazMJnmW9Wezc3IeE PHxXnjh4 YlffyxH11VcIj0Jl2Mn3gHlbNElOsOBmxDNP5IJ48GWFtXixC0Bua4G70Fr8BdaBp4L0PhbIVLyi+LKLjSCQJz2Xco11+/E65N3q8llLxdXcs3rADys/FzXJAX1qo2lVk69PfIP4EiFDGcoIYl8XB9n6ooWbHFTrSPwqTVdefV10gY0JuO2+Z/HqlMBbFkZc4hy0LiRTvLUicfcMI5oDmnbETjkNGpFckxJbeOx0J7DRO54L71wNNH1MHs0f+Vma2pDKfupM2kqIbvTsGWug9yuFOcQ== 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: Changes v6 -> v7: - Rebased on top of Andrey Konovalov's libstackdepot patchset - Reformulated the changelogs Changes v5 -> v6: - Rebase on top of v6.7-rc1 - Move stack_record struct to the header - Addressed feedback from Vlastimil (some code tweaks and changelogs suggestions) Changes v4 -> v5: - Addressed feedback from 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) page_owner is a great debug functionality tool that lets us know about all pages that have been allocated/freed and their specific stacktrace. This comes very handy when debugging memory leaks, since with some scripting we can see the outstanding allocations, which might point to a memory leak. In my experience, that is one of the most useful cases, but it can get really tedious to screen through all pages and try to reconstruct the stack <-> allocated/freed relationship, becoming most of the time a daunting and slow process when we have tons of allocation/free operations. This patchset aims to ease that by adding a new functionality into page_owner. This functionality creates a new read-only file called "page_owner_stacks", which prints out all the stacks followed by their outstanding number of allocations (being that the times the stacktrace has allocated but not freed yet). This gives us a clear and a quick overview of stacks <-> allocated/free. We take advantage of the new refcount_f field that stack_record struct gained, and increment/decrement the stack refcount on every __set_page_owner() (alloc operation) and __reset_page_owner (free operation) call. Unfortunately, we cannot use the new stackdepot api STACK_DEPOT_FLAG_{GET,PUT} because it does not fulfill page_owner needs, meaning we would have to special case things, at which point makes more sense for page_owner to do its own {dec,inc}rementing of the stacks. E.g: Using STACK_DEPOT_FLAG_PUT, once the refcount reaches 0, such stack gets evicted, so page_owner would lose information. This patch also creates a new file called 'page_owner_threshold'. By writing a value to it, the stacks which refcount is below such value will be filtered out. In order to better exercise the path in stack_depot_get_next_stack(), I artificially filled the buckets with more than one stack, making sure I was getting all of then when reading from it. On a side note, stack_depot_get_next_stack() could be somehow reconstructed to be in page_owner code, but we would have to move stack_table into the header, so page_owner can access it. I can do that if that's preferred, so stackdepot.c would not get "poluted". A PoC can be found below: # cat /sys/kernel/debug/page_owner_stacks > page_owner_full_stacks.txt # head -40 page_owner_full_stacks.txt 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 page_cache_ra_unbounded+0x96/0x180 filemap_get_pages+0xfd/0x590 filemap_read+0xcc/0x330 blkdev_read_iter+0xb8/0x150 vfs_read+0x285/0x320 ksys_read+0xa5/0xe0 do_syscall_64+0x80/0x160 entry_SYSCALL_64_after_hwframe+0x6e/0x76 stack_count: 521 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: 4609 ... ... # echo 5000 > /sys/kernel/debug/page_owner_threshold # cat /sys/kernel/debug/page_owner_stacks > page_owner_full_stacks_5000.txt # head -40 page_owner_full_stacks_5000.txt 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_pwrite64+0x75/0x90 do_syscall_64+0x80/0x160 entry_SYSCALL_64_after_hwframe+0x6e/0x76 stack_count: 6781 prep_new_page+0xa9/0x120 get_page_from_freelist+0x801/0x2210 __alloc_pages+0x18b/0x350 pcpu_populate_chunk+0xec/0x350 pcpu_balance_workfn+0x2d1/0x4a0 process_scheduled_works+0x84/0x380 worker_thread+0x12a/0x2a0 kthread+0xe3/0x110 ret_from_fork+0x30/0x50 ret_from_fork_asm+0x1b/0x30 stack_count: 8641 Oscar Salvador (4): lib/stackdepot: Move stack_record struct definition into the header mm,page_owner: Implement the tracking of the stacks count mm,page_owner: Display all stacks and their count mm,page_owner: Filter out stacks by a threshold include/linux/stackdepot.h | 72 ++++++++++++++++++++ lib/stackdepot.c | 97 ++++++++++++++------------ mm/page_owner.c | 136 +++++++++++++++++++++++++++++++++++++ 3 files changed, 262 insertions(+), 43 deletions(-)