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[198.145.29.99]) by mx.google.com with ESMTPS id q19si13413434pgg.521.2019.07.23.16.14.13 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 23 Jul 2019 16:14:13 -0700 (PDT) Received-SPF: pass (google.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) client-ip=198.145.29.99; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b="H/is+lPc"; spf=pass (google.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org Received: from akpm3.svl.corp.google.com (unknown [104.133.8.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id CCC282253D; Tue, 23 Jul 2019 23:14:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1563923653; bh=lw124mTrOq6s0ksdXzyc2Oln5pXIDUq4BhFKcu/YBF4=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=H/is+lPc7+MKPGbjO35Cz5fZMCCV+SCv/slPD8z/ItwgSn0sCA7qrhYwzbs1cNdgc 7u0uumNpvlVdqyqDWXMgpXzMRSQC+J6JKOIuiywlZEaaSNvRn9O9aj31fRJtu5YbNK ReZIdHzhA+xVJxkRJuAJXAXr54GoumPP076glx6Q= Date: Tue, 23 Jul 2019 16:14:12 -0700 From: Andrew Morton To: Tetsuo Handa Cc: linux-mm@kvack.org, Michal Hocko , Roman Gushchin , Shakeel Butt Subject: Re: [PATCH] mm, oom: avoid printk() iteration under RCU Message-Id: <20190723161412.df47e0c9ecd8bc28d3183604@linux-foundation.org> In-Reply-To: <1563360901-8277-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> References: <1563360901-8277-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, 17 Jul 2019 19:55:01 +0900 Tetsuo Handa wrote: > Currently dump_tasks() might call printk() for many thousands times under > RCU, which might take many minutes for slow consoles. Therefore, split > dump_tasks() into three stages; take a snapshot of possible OOM victim > candidates under RCU, dump the snapshot from reschedulable context, and > destroy the snapshot. > > In a future patch, the first stage would be moved to select_bad_process() > and the third stage would be moved to after oom_kill_process(), and will > simplify refcount handling. Look straightforward enough. > > ... > > static void dump_tasks(struct oom_control *oc) > { > - pr_info("Tasks state (memory values in pages):\n"); > - pr_info("[ pid ] uid tgid total_vm rss pgtables_bytes swapents oom_score_adj name\n"); > + static LIST_HEAD(list); I don't think this needs to be static? > + struct task_struct *p; > + struct task_struct *t; > > if (is_memcg_oom(oc)) > - mem_cgroup_scan_tasks(oc->memcg, dump_task, oc); > + mem_cgroup_scan_tasks(oc->memcg, add_candidate_task, &list); > else { > - struct task_struct *p; > - > rcu_read_lock(); > for_each_process(p) > - dump_task(p, oc); > + add_candidate_task(p, &list); > rcu_read_unlock(); > } > + pr_info("Tasks state (memory values in pages):\n"); > + pr_info("[ pid ] uid tgid total_vm rss pgtables_bytes swapents oom_score_adj name\n"); > + list_for_each_entry(p, &list, oom_victim_list) { > + cond_resched(); > + /* p may not have freeable memory in nodemask */ > + if (!is_memcg_oom(oc) && !oom_cpuset_eligible(p, oc)) > + continue; > + /* All of p's threads might have already detached their mm's. */ > + t = find_lock_task_mm(p); > + if (!t) > + continue; > + pr_info("[%7d] %5d %5d %8lu %8lu %8ld %8lu %5hd %s\n", > + t->pid, from_kuid(&init_user_ns, task_uid(t)), > + t->tgid, t->mm->total_vm, get_mm_rss(t->mm), > + mm_pgtables_bytes(t->mm), > + get_mm_counter(t->mm, MM_SWAPENTS), > + t->signal->oom_score_adj, t->comm); > + task_unlock(t); > + } > + list_for_each_entry_safe(p, t, &list, oom_victim_list) { > + list_del(&p->oom_victim_list); > + put_task_struct(p); > + } > }