On Mon, Aug 16, 2021 at 11:09:08AM -0700, 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 > > The lockup made the machine is quite unusable. And it also made the > most workingset gone, the reclaimabled slab caches were reduced from 12G > to 300MB, the page caches were decreased from 17G to 4G. > > But the most disappointing thing is all the effort doesn't make the page > offline, it just returns: > > soft_offline: 0x1469f2: unknown non LRU page type 5ffff0000000000 () > > It seems the aggressive behavior for non-LRU page didn't pay back, so it > doesn't make too much sense to keep it considering the terrible side > effect. > > Reported-by: David Mackey <tdmackey@xxxxxxxxxxx> > Cc: Naoya Horiguchi <naoya.horiguchi@xxxxxxx> > Cc: Oscar Salvador <osalvador@xxxxxxx> > Signed-off-by: Yang Shi <shy828301@xxxxxxxxx> Thank you. I agree with the idea of dropping drop_slab_node() in shake_page(), hoping that range-based slab shrinker will be implemented in the future. This patch conflicts with the patch https://lore.kernel.org/linux-mm/20210817053703.2267588-1-naoya.horiguchi@xxxxxxxxx/T/#u which adds another shake_page(), so could you add the following hunk in your patch? diff --git a/mm/memory-failure.c b/mm/memory-failure.c index 64f8ac969544..7dd2ca665866 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -1198,7 +1198,7 @@ static int get_any_page(struct page *p, unsigned long flags) * page, retry. */ if (pass++ < 3) { - shake_page(p, 1); + shake_page(p); goto try_again; } goto out; Thanks, Naoya Horiguchi
