On Sat, 26 Jan 2019 21:00:05 +0100, Pavel Machek said: > top - 13:38:51 up 1:42, 16 users, load average: 1.41, 1.93, 1.62 > Tasks: 182 total, 3 running, 138 sleeping, 0 stopped, 0 zombie > %Cpu(s): 2.3 us, 57.8 sy, 0.0 ni, 39.9 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 > st > KiB Mem: 3020044 total, 2429420 used, 590624 free, 27468 buffers > KiB Swap: 2097148 total, 0 used, 2097148 free. 1924268 cached Mem > > PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND > 608 root 20 0 0 0 0 R 99.6 0.0 11:34.38 kcompactd0 > 9782 root 20 0 0 0 0 I 7.9 0.0 0:59.02 kworker/0: > 2971 root 20 0 46624 23076 13576 S 4.3 0.8 2:50.22 Xorg
I've noticed this as well on earlier kernels (next-20181224 to 20190115) Some more info: 1) echo 3 > /proc/sys/vm/drop_caches unwedges kcompactd in 1-3 seconds. 2) Typical kcompactd traceback: cat /proc/27/stack [<0>] retint_kernel+0x1b/0x2d [<0>] lock_is_held_type+0x1b/0x50 [<0>] ___might_sleep+0xad/0x220 [<0>] __might_sleep+0x113/0x130 [<0>] on_each_cpu_cond_mask+0x12a/0x140 [<0>] on_each_cpu_cond+0x18/0x20 [<0>] invalidate_bh_lrus+0x29/0x30 [<0>] __buffer_migrate_page+0x154/0x340 [<0>] buffer_migrate_page_norefs+0x14/0x20 [<0>] move_to_new_page+0x8e/0x360 [<0>] migrate_pages+0x3cc/0xfd8 [<0>] compact_zone+0xb70/0x1380 [<0>] kcompactd_do_work+0x15b/0x500 [<0>] kcompactd+0x74/0x340 [<0>] kthread+0x158/0x170 [<0>] ret_from_fork+0x3a/0x50 [<0>] 0xffffffffffffffff I've also seen khugepaged hung up: cat /proc/29/stack [<0>] ___preempt_schedule+0x16/0x18 [<0>] page_vma_mapped_walk+0x60/0x840 [<0>] remove_migration_pte+0x67/0x390 [<0>] rmap_walk_file+0x186/0x380 [<0>] rmap_walk+0xa3/0xd0 [<0>] remove_migration_ptes+0x69/0x70 [<0>] migrate_pages+0xb6d/0xfd8 [<0>] compact_zone+0xb70/0x1370 [<0>] compact_zone_order+0xd8/0x120 [<0>] try_to_compact_pages+0xe5/0x550 [<0>] __alloc_pages_direct_compact+0x6d/0x1a0 [<0>] __alloc_pages_slowpath+0x6c9/0x1640 [<0>] __alloc_pages_nodemask+0x558/0x5b0 [<0>] khugepaged+0x499/0x810 [<0>] kthread+0x158/0x170 [<0>] ret_from_fork+0x3a/0x50 [<0>] 0xffffffffffffffff Looks like something has gone astray with compact_zone.
