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Date: Mon, 28 Jan 2019 10:18:27 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
Michal Hocko <mhocko@...nel.org>
Cc: Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
Andrew Morton <akpm@...ux-foundation.org>,
Johannes Weiner <hannes@...xchg.org>,
linux-kernel@...r.kernel.org, linux-mm <linux-mm@...ck.org>,
Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: Re: [linux-next] kcompactd0 stuck in a CPU-burning loop
On 1/28/19 9:57 AM, Sergey Senozhatsky wrote:
> Hello,
>
> next-20190125
>
> kcompactd0 is spinning on something, burning CPUs in the meantime:
Hi, could you check/add this to the earlier thread? Thanks.
https://lore.kernel.org/lkml/20190126200005.GB27513@amd/T/#u
>
> %CPU TIME+ COMMAND
> 100.0 0.0 34:04.20 R [kcompactd0]
>
> Not sure I know how to reproduce it; so am probably not going to
> be a very helpful tester.
>
> I tried to ftrace kcompactd0 PID, and I see the same path all over
> the tracing file:
>
> 2) 0.119 us | unlock_page();
> 2) 0.109 us | unlock_page();
> 2) 0.096 us | compaction_free();
> 2) 0.104 us | ___might_sleep();
> 2) 0.121 us | compaction_alloc();
> 2) 0.111 us | page_mapped();
> 2) 0.105 us | page_mapped();
> 2) | move_to_new_page() {
> 2) 0.102 us | page_mapping();
> 2) | buffer_migrate_page_norefs() {
> 2) | __buffer_migrate_page() {
> 2) | expected_page_refs() {
> 2) 0.118 us | page_mapping();
> 2) 0.321 us | }
> 2) | __might_sleep() {
> 2) 0.122 us | ___might_sleep();
> 2) 0.332 us | }
> 2) | _raw_spin_lock() {
> 2) 0.115 us | preempt_count_add();
> 2) 0.321 us | }
> 2) | _raw_spin_unlock() {
> 2) 0.114 us | preempt_count_sub();
> 2) 0.321 us | }
> 2) | invalidate_bh_lrus() {
> 2) | on_each_cpu_cond() {
> 2) | on_each_cpu_cond_mask() {
> 2) | __might_sleep() {
> 2) 0.114 us | ___might_sleep();
> 2) 0.316 us | }
> 2) 0.109 us | preempt_count_add();
> 2) 0.128 us | has_bh_in_lru();
> 2) 0.105 us | has_bh_in_lru();
> 2) 0.124 us | has_bh_in_lru();
> 2) 0.103 us | has_bh_in_lru();
> 2) 0.125 us | has_bh_in_lru();
> 2) 0.105 us | has_bh_in_lru();
> 2) 0.123 us | has_bh_in_lru();
> 2) 0.107 us | has_bh_in_lru();
> 2) | on_each_cpu_mask() {
> 2) 0.104 us | preempt_count_add();
> 2) 0.110 us | smp_call_function_many();
> 2) 0.105 us | preempt_count_sub();
> 2) 0.764 us | }
> 2) 0.116 us | preempt_count_sub();
> 2) 3.676 us | }
> 2) 3.889 us | }
> 2) 4.087 us | }
> 2) | _raw_spin_lock() {
> 2) 0.112 us | preempt_count_add();
> 2) 0.315 us | }
> 2) | _raw_spin_unlock() {
> 2) 0.108 us | preempt_count_sub();
> 2) 0.309 us | }
> 2) | unlock_buffer() {
> 2) | wake_up_bit() {
> 2) 0.118 us | __wake_up_bit();
> 2) 0.317 us | }
> 2) 0.513 us | }
> 2) 7.440 us | }
> 2) 7.643 us | }
> 2) 8.070 us | }
>
>
> PG migration fails a lot:
>
> pgmigrate_success 111063
> pgmigrate_fail 269841559
> compact_migrate_scanned 536253365
> compact_free_scanned 360889
> compact_isolated 270072733
> compact_stall 0
> compact_fail 0
> compact_success 0
> compact_daemon_wake 56
> compact_daemon_migrate_scanned 536253365
> compact_daemon_free_scanned 360889
>
> Let me know if I can help with anything else. I'll keep the the box alive
> for a while, but will have to power it off eventually.
>
> -ss
>
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