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[209.85.220.65]) by mx.google.com with SMTPS id y196sor6431082ywy.56.2019.06.17.09.48.54 for (Google Transport Security); Mon, 17 Jun 2019 09:48:54 -0700 (PDT) Received-SPF: pass (google.com: domain of shakeelb@google.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=DYbfUmrC; spf=pass (google.com: domain of shakeelb@google.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=shakeelb@google.com; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=+bhc7wfVjCBaM/En8KIXc3jvZNzrMiSbZDMErO7mmcg=; b=DYbfUmrCCAumnmXWODR8+LTnOQ7KCdpvfaHsby+TAizkhkgf9X+hDwVKW4YCRvdsbR /DOd5z4sNTjXhhHg4CBJHxUJprspmaW8XaWIiWkX+EV8vLcn2YwQSz+9l1BWRwYW+73b sRLre+0lZ4TKnygun0iG/ayZWy5ATKzXzNZl5MrbxQC3DEEIjRdnA13dv/ZlgoicmAOp g+jvdpAKS2ONslZ6WLqsoHuzSs2omaxjORyd3O7XTFtCOfvPuIEcfVq6Aw0u+QZRs2wk T+cp2SBxHX7+kuygOvMGZO3uv0/dBlh/APwxh1cjz+fNoqmHVtoZvU29KFhUYSks2J70 GFHA== X-Google-Smtp-Source: APXvYqxYDlg2DGtdAFSTrNecvf6mKBN+e0hfaf7Tt/m0UWAiagrxescZo68t6wSXRTD7aC9x4EqbsMND7aHUQSudaIQ= X-Received: by 2002:a81:a55:: with SMTP id 82mr29118544ywk.205.1560790134326; Mon, 17 Jun 2019 09:48:54 -0700 (PDT) MIME-Version: 1.0 References: <20190617155954.155791-1-shakeelb@google.com> <20190617161702.GE1492@dhcp22.suse.cz> In-Reply-To: <20190617161702.GE1492@dhcp22.suse.cz> From: Shakeel Butt Date: Mon, 17 Jun 2019 09:48:42 -0700 Message-ID: Subject: Re: [PATCH] mm, oom: fix oom_unkillable_task for memcg OOMs To: Michal Hocko Cc: Johannes Weiner , Tetsuo Handa , Andrew Morton , Roman Gushchin , Linux MM , LKML Content-Type: text/plain; charset="UTF-8" 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 Mon, Jun 17, 2019 at 9:17 AM Michal Hocko wrote: > > On Mon 17-06-19 08:59:54, Shakeel Butt wrote: > > Currently oom_unkillable_task() checks mems_allowed even for memcg OOMs > > which does not make sense as memcg OOMs can not be triggered due to > > numa constraints. Fixing that. > > > > Also if memcg is given, oom_unkillable_task() will check the task's > > memcg membership as well to detect oom killability. However all the > > memcg related code paths leading to oom_unkillable_task(), other than > > dump_tasks(), come through mem_cgroup_scan_tasks() which traverses > > tasks through memcgs. Once dump_tasks() is converted to use > > mem_cgroup_scan_tasks(), there is no need to do memcg membership check > > in oom_unkillable_task(). > > I think this patch just does too much in one go. Could you split out > the dump_tasks part and the oom_unkillable_task parts into two patches > please? It should be slightly easier to review. > Yes, will do in v2. > [...] > > +static bool oom_unkillable_task(struct task_struct *p, struct oom_control *oc) > > { > > if (is_global_init(p)) > > return true; > > if (p->flags & PF_KTHREAD) > > return true; > > + if (!oc) > > + return false; > > Bah, this is just too ugly. AFAICS this is only because oom_score still > uses oom_unkillable_task which is kinda dubious, no? While you are > touching this code, can we remove this part as well? I would be really > surprised if any code really depends on ineligible tasks reporting 0 > oom_score. I think it is safer to just localize the is_global_init() and PF_KTHREAD checks in oom_badness() instead of invoking oom_unkillable_task(). Also I think cpuset_mems_allowed_intersects() check from /proc/[pid]/oom_score is unintentional. Shakeel