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bh=8unrTvKae6m1mp7QwRwUZgVhor5hVomY1M8CRyhx1+4=; b=4iJa5KHa5G3udu4cYxTwrhisV3qDcqzgp9iKYP1HmNAOR1KCV1nBJqTtUQwANb1CyUR9MD SVvPUSSrU4UxLGBw== 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 AC94C137DA; Mon, 6 Jan 2025 08:45:52 +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 jYUVKUCYe2cBYwAAD6G6ig (envelope-from ); Mon, 06 Jan 2025 08:45:52 +0000 Message-ID: <1ea309c1-d0f8-4209-b0b0-e69ad4e986ae@suse.cz> Date: Mon, 6 Jan 2025 09:45:52 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] memcg: fix soft lockup in the OOM process To: Chen Ridong , akpm@linux-foundation.org, mhocko@kernel.org, hannes@cmpxchg.org, yosryahmed@google.com, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, davidf@vimeo.com, handai.szj@taobao.com, rientjes@google.com, kamezawa.hiroyu@jp.fujitsu.com, RCU Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, chenridong@huawei.com, wangweiyang2@huawei.com References: <20241224025238.3768787-1-chenridong@huaweicloud.com> Content-Language: en-US From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: D67DE21161 X-Spam-Score: -4.51 X-Rspamd-Action: no action X-Spamd-Result: default: False [-4.51 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; RCVD_TLS_ALL(0.00)[]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; RCPT_COUNT_TWELVE(0.00)[18]; MID_RHS_MATCH_FROM(0.00)[]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; TO_DN_SOME(0.00)[]; FROM_HAS_DN(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DKIM_TRACE(0.00)[suse.cz:+] X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Spam-Flag: NO X-Spam-Level: On 12/24/24 03:52, Chen Ridong wrote: > From: Chen Ridong +CC RCU > A soft lockup issue was found in the product with about 56,000 tasks were > in the OOM cgroup, it was traversing them when the soft lockup was > triggered. > > watchdog: BUG: soft lockup - CPU#2 stuck for 23s! [VM Thread:1503066] > CPU: 2 PID: 1503066 Comm: VM Thread Kdump: loaded Tainted: G > Hardware name: Huawei Cloud OpenStack Nova, BIOS > RIP: 0010:console_unlock+0x343/0x540 > RSP: 0000:ffffb751447db9a0 EFLAGS: 00000247 ORIG_RAX: ffffffffffffff13 > RAX: 0000000000000001 RBX: 0000000000000000 RCX: 00000000ffffffff > RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000247 > RBP: ffffffffafc71f90 R08: 0000000000000000 R09: 0000000000000040 > R10: 0000000000000080 R11: 0000000000000000 R12: ffffffffafc74bd0 > R13: ffffffffaf60a220 R14: 0000000000000247 R15: 0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00007f2fe6ad91f0 CR3: 00000004b2076003 CR4: 0000000000360ee0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > vprintk_emit+0x193/0x280 > printk+0x52/0x6e > dump_task+0x114/0x130 > mem_cgroup_scan_tasks+0x76/0x100 > dump_header+0x1fe/0x210 > oom_kill_process+0xd1/0x100 > out_of_memory+0x125/0x570 > mem_cgroup_out_of_memory+0xb5/0xd0 > try_charge+0x720/0x770 > mem_cgroup_try_charge+0x86/0x180 > mem_cgroup_try_charge_delay+0x1c/0x40 > do_anonymous_page+0xb5/0x390 > handle_mm_fault+0xc4/0x1f0 > > This is because thousands of processes are in the OOM cgroup, it takes a > long time to traverse all of them. As a result, this lead to soft lockup > in the OOM process. > > To fix this issue, call 'cond_resched' in the 'mem_cgroup_scan_tasks' > function per 1000 iterations. For global OOM, call > 'touch_softlockup_watchdog' per 1000 iterations to avoid this issue. > > Fixes: 9cbb78bb3143 ("mm, memcg: introduce own oom handler to iterate only over its own threads") > Signed-off-by: Chen Ridong > --- > mm/memcontrol.c | 7 ++++++- > mm/oom_kill.c | 8 +++++++- > 2 files changed, 13 insertions(+), 2 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 65fb5eee1466..46f8b372d212 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -1161,6 +1161,7 @@ void mem_cgroup_scan_tasks(struct mem_cgroup *memcg, > { > struct mem_cgroup *iter; > int ret = 0; > + int i = 0; > > BUG_ON(mem_cgroup_is_root(memcg)); > > @@ -1169,8 +1170,12 @@ void mem_cgroup_scan_tasks(struct mem_cgroup *memcg, > struct task_struct *task; > > css_task_iter_start(&iter->css, CSS_TASK_ITER_PROCS, &it); > - while (!ret && (task = css_task_iter_next(&it))) > + while (!ret && (task = css_task_iter_next(&it))) { > + /* Avoid potential softlockup warning */ > + if ((++i & 1023) == 0) > + cond_resched(); > ret = fn(task, arg); > + } > css_task_iter_end(&it); > if (ret) { > mem_cgroup_iter_break(memcg, iter); > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > index 1c485beb0b93..044ebab2c941 100644 > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -44,6 +44,7 @@ > #include > #include > #include > +#include > > #include > #include "internal.h" > @@ -430,10 +431,15 @@ static void dump_tasks(struct oom_control *oc) > mem_cgroup_scan_tasks(oc->memcg, dump_task, oc); > else { > struct task_struct *p; > + int i = 0; > > rcu_read_lock(); > - for_each_process(p) > + for_each_process(p) { > + /* Avoid potential softlockup warning */ > + if ((++i & 1023) == 0) > + touch_softlockup_watchdog(); This might suppress the soft lockup, but won't a rcu stall still be detected? > dump_task(p, oc); > + } > rcu_read_unlock(); > } > }