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[91.12.103.241]) by smtp.gmail.com with ESMTPSA id y11sm88016wru.0.2021.08.16.12.04.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 16 Aug 2021 12:04:49 -0700 (PDT) Subject: Re: [PATCH 1/2] mm: hwpoison: don't drop slab caches for offlining non-LRU page From: David Hildenbrand To: Yang Shi , naoya.horiguchi@nec.com, osalvador@suse.de, tdmackey@twitter.com, akpm@linux-foundation.org, corbet@lwn.net Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20210816180909.3603-1-shy828301@gmail.com> <2ea04811-a9a3-0fe6-38aa-222e79ded09a@redhat.com> Organization: Red Hat Message-ID: Date: Mon, 16 Aug 2021 21:04:48 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <2ea04811-a9a3-0fe6-38aa-222e79ded09a@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 16.08.21 21:02, David Hildenbrand wrote: > On 16.08.21 20:09, Yang Shi wrote: >> In the current implementation of soft offline, if non-LRU page is met, >> all the slab caches will be dropped to free the page then offline. But >> if the page is not slab page all the effort is wasted in vain. Even >> though it is a slab page, it is not guaranteed the page could be freed >> at all. >> >> However the side effect and cost is quite high. It does not only drop >> the slab caches, but also may drop a significant amount of page caches >> which are associated with inode caches. It could make the most >> workingset gone in order to just offline a page. And the offline is not >> guaranteed to succeed at all, actually I really doubt the success rate >> for real life workload. >> >> Furthermore the worse consequence is the system may be locked up and >> unusable since the page cache release may incur huge amount of works >> queued for memcg release. >> >> Actually we ran into such unpleasant case in our production environment. >> Firstly, the workqueue of memory_failure_work_func is locked up as >> below: >> >> BUG: workqueue lockup - pool cpus=1 node=0 flags=0x0 nice=0 stuck for 53s! >> Showing busy workqueues and worker pools: >> workqueue events: flags=0x0 >>   pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=14/256 refcnt=15 >>     in-flight: 409271:memory_failure_work_func >>     pending: kfree_rcu_work, kfree_rcu_monitor, kfree_rcu_work, rht_deferred_worker, rht_deferred_worker, rht_deferred_worker, rht_deferred_worker, kfree_rcu_work, kfree_rcu_work, kfree_rcu_work, kfree_rcu_work, drain_local_stock, kfree_rcu_work >> workqueue mm_percpu_wq: flags=0x8 >>   pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/256 refcnt=2 >>     pending: vmstat_update >> workqueue cgroup_destroy: flags=0x0 >> pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/1 refcnt=12072 >> pending: css_release_work_fn >> >> There were over 12K css_release_work_fn queued, and this caused a few >> lockups due to the contention of worker pool lock with IRQ disabled, for >> example: >> >> NMI watchdog: Watchdog detected hard LOCKUP on cpu 1 >> Modules linked in: amd64_edac_mod edac_mce_amd crct10dif_pclmul crc32_pclmul ghash_clmulni_intel xt_DSCP iptable_mangle kvm_amd bpfilter vfat fat acpi_ipmi i2c_piix4 usb_storage ipmi_si k10temp i2c_core ipmi_devintf ipmi_msghandler acpi_cpufreq sch_fq_codel xfs libcrc32c crc32c_intel mlx5_core mlxfw nvme xhci_pci ptp nvme_core pps_core xhci_hcd >> CPU: 1 PID: 205500 Comm: kworker/1:0 Tainted: G L 5.10.32-t1.el7.twitter.x86_64 #1 >> Hardware name: TYAN F5AMT /z /S8026GM2NRE-CGN, BIOS V8.030 03/30/2021 >> Workqueue: events memory_failure_work_func >> RIP: 0010:queued_spin_lock_slowpath+0x41/0x1a0 >> Code: 41 f0 0f ba 2f 08 0f 92 c0 0f b6 c0 c1 e0 08 89 c2 8b 07 30 e4 09 d0 a9 00 01 ff ff 75 1b 85 c0 74 0e 8b 07 84 c0 74 08 f3 90 <8b> 07 84 c0 75 f8 b8 01 00 00 00 66 89 07 c3 f6 c4 01 75 04 c6 47 >> RSP: 0018:ffff9b2ac278f900 EFLAGS: 00000002 >> RAX: 0000000000480101 RBX: ffff8ce98ce71800 RCX: 0000000000000084 >> RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8ce98ce6a140 >> RBP: 00000000000284c8 R08: ffffd7248dcb6808 R09: 0000000000000000 >> R10: 0000000000000003 R11: ffff9b2ac278f9b0 R12: 0000000000000001 >> R13: ffff8cb44dab9c00 R14: ffffffffbd1ce6a0 R15: ffff8cacaa37f068 >> FS: 0000000000000000(0000) GS:ffff8ce98ce40000(0000) knlGS:0000000000000000 >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> CR2: 00007fcf6e8cb000 CR3: 0000000a0c60a000 CR4: 0000000000350ee0 >> Call Trace: >> __queue_work+0xd6/0x3c0 >> queue_work_on+0x1c/0x30 >> uncharge_batch+0x10e/0x110 >> mem_cgroup_uncharge_list+0x6d/0x80 >> release_pages+0x37f/0x3f0 >> __pagevec_release+0x1c/0x50 >> __invalidate_mapping_pages+0x348/0x380 >> ? xfs_alloc_buftarg+0xa4/0x120 [xfs] >> inode_lru_isolate+0x10a/0x160 >> ? iput+0x1d0/0x1d0 >> __list_lru_walk_one+0x7b/0x170 >> ? iput+0x1d0/0x1d0 >> list_lru_walk_one+0x4a/0x60 >> prune_icache_sb+0x37/0x50 >> super_cache_scan+0x123/0x1a0 >> do_shrink_slab+0x10c/0x2c0 >> shrink_slab+0x1f1/0x290 >> drop_slab_node+0x4d/0x70 >> soft_offline_page+0x1ac/0x5b0 >> ? dev_mce_log+0xee/0x110 >> ? notifier_call_chain+0x39/0x90 >> memory_failure_work_func+0x6a/0x90 >> process_one_work+0x19e/0x340 >> ? process_one_work+0x340/0x340 >> worker_thread+0x30/0x360 >> ? process_one_work+0x340/0x340 >> kthread+0x116/0x130 > > Just curious, who actually ends up calling soft_offline_page() ? I > cannot really make sense of this, looking at upstream Linux. > > I can spot > > a) drivers/base/memory.c: /sys/devices/system/memory/soft_offline_page > seems to be a testing interface > > b) MADV_SOFT_OFFLINE seems to be a testing interface as well > > c) arch/parisc/kernel/pdt.c doesn't apply to your case I guess? > > I'm just wondering who ends up calling soft_offline_page() in a > production environment and via which call path. I'm most probably > missing something. > ... and I missed memory_failure_work_func() with MF_SOFT_OFFLINE :) Ignore my question :) -- Thanks, David / dhildenb