From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2E0D1CA0EF8 for ; Wed, 20 Aug 2025 22:50:06 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B19E98E0039; Wed, 20 Aug 2025 18:50:05 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id ACA498E0031; Wed, 20 Aug 2025 18:50:05 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9B8CC8E0039; Wed, 20 Aug 2025 18:50:05 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 86C408E0031 for ; Wed, 20 Aug 2025 18:50:05 -0400 (EDT) Received: from smtpin12.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 4536EC015B for ; Wed, 20 Aug 2025 22:50:05 +0000 (UTC) X-FDA: 83798630370.12.C73C184 Received: from out-183.mta1.migadu.com (out-183.mta1.migadu.com [95.215.58.183]) by imf01.hostedemail.com (Postfix) with ESMTP id 00E2140011 for ; Wed, 20 Aug 2025 22:50:01 +0000 (UTC) Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=nB9asYOT; spf=pass (imf01.hostedemail.com: domain of roman.gushchin@linux.dev designates 95.215.58.183 as permitted sender) smtp.mailfrom=roman.gushchin@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1755730202; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=UsdDNWT0aPaFWkXNVMSJrwjwzzlXY8/IesqRJaJrUFg=; b=tbJk2b1QK5riCLb2EXOM6z4LQE50NJ9xr4I/0MfNf6tImFiAQDcbimGOfxr7IIku1FfnXo S1msyyAiADjEngmbVDgiRZQ8wrPz5rSDeHESw83w+1P4SU5NK07Tsomk5Efd7+H8v05euS JxdLGJIuQzmC2m+KbDUrfd/Tomhfk8Q= ARC-Authentication-Results: i=1; imf01.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=nB9asYOT; spf=pass (imf01.hostedemail.com: domain of roman.gushchin@linux.dev designates 95.215.58.183 as permitted sender) smtp.mailfrom=roman.gushchin@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1755730202; a=rsa-sha256; cv=none; b=r0kKeIcvKNqDj9ra/y9Fm2BHwkSSz+rUOwDf5LLdQq3kKN0LDeUmzNQMm9t3hfGd0d57Ho MrNL/ybqa3IPF2q40954aaLCIg7ca2RuSDNmOmO7h+AQADZ+05j3cjr1mdcapVe1yLlhwf zu1o29BuHOb0fbFB7aAuvw0Spj65W8A= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1755730200; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=UsdDNWT0aPaFWkXNVMSJrwjwzzlXY8/IesqRJaJrUFg=; b=nB9asYOTay3SplClMlGUjqJrUlNm40iBpD5ePjlHlcko7ltyfZdyC8gCY3jD40zA+3I/ZU UINeNtc0dBEbM/WktZuxCAHr4Af/b1uEbFb0lAqxvpNyZU8B1+B1tmnxpcRHvi2ZRfyOR/ NZWzYbGQCeZ/LrkD4Df+fjs3Ag8mOic= From: Roman Gushchin To: Kumar Kartikeya Dwivedi Cc: linux-mm@kvack.org, bpf@vger.kernel.org, Suren Baghdasaryan , Johannes Weiner , Michal Hocko , David Rientjes , Matt Bobrowski , Song Liu , Alexei Starovoitov , Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: [PATCH v1 10/14] bpf: selftests: bpf OOM handler test In-Reply-To: (Kumar Kartikeya Dwivedi's message of "Wed, 20 Aug 2025 11:33:42 +0200") References: <20250818170136.209169-1-roman.gushchin@linux.dev> <20250818170136.209169-11-roman.gushchin@linux.dev> Date: Wed, 20 Aug 2025 15:49:53 -0700 Message-ID: <878qjdobfy.fsf@linux.dev> MIME-Version: 1.0 Content-Type: text/plain X-Migadu-Flow: FLOW_OUT X-Stat-Signature: 1mxo9giosd619uyb3x665som7d3bedcc X-Rspam-User: X-Rspamd-Queue-Id: 00E2140011 X-Rspamd-Server: rspam05 X-HE-Tag: 1755730201-16995 X-HE-Meta: U2FsdGVkX1+X2VRMoy1G73tXHNeHTFTfgbRYHISOxRjalemDai+8hg1/l0V0QHGbgHmJAsslkjxBsIEe7QxtN3AHXPPSynX/2gqnbA3ofFRMSR3qziYPxOBk6rRfO905WH0pe1In1MGeOeNzIXRTB7xZOQE4EeanWESkN+3HYtmot59RCpVJbWw3f3AHCYtlGMcry+zhcpIniiEVJ/dkcNwfWzsU76sR+6FTrRbEOYU41bA9LuewKoJAPopdUmuZHMJhJBsvAG/ajR4dmhToC+Gzdh3T5Eg6iEvpq66n5G3jJcXM0mYftHpljxmeWpTul7R5m+3d9APhXniFGh6ODKJkKHbmqQ/HAI0NEJujj5TdPHE4k7lJICaDXgVEryKSgLaotJUg/pgfpeVBnndpKF2Ks2rop9BukcArXNc1p+AQQ7kL/uiltVe+Tp+aaZdwb9HI+lLYpMxjpmMBA2ogJ1be/B0sc2BtrBD8VpBO1rH/LnPzmnTSGOSwe3LHf0SHENXDx/rmxSj8XYMeihaGVLeK742N3akHY3Wg4+//SAcZnDB5izMxHUNQ79u6s7r4JC7m7l5oXHDpIp8CwDlVsScJp/32t7t2NKlvndafZ1knOks2lXjEkkQ13M2RGorh74qM6s3zvFiS8JqXZShIU4Ii//B96OxwQuPpTjazDdi7LEBZ3q0MgXMWV0nEU9eFD7cBH1bmQQ0k/ca+N9OPCml1DfPXluEnVBeGwbuDPmxBxrMw65CQIUL9V/IMBVnb4APYWDiYHfI3YZx5Kb352ddC07sD3JCXEqETXfJIS6vYBHaJoLKFuuO1cn57ldToGJ9CbGHX9Xi/d+KhfalunHPdMXKacMZQzdlU9AWxjTiBWvf4bHCkjw9x3O7VFBh2Nm1UsTeySKm1nyLvFqWi1nHd5I1D5NBsQ3fxmqO6o5jN5xUoxU87m39Lfy4jSr1t/9YvcRBfiZ7MPRUSViT R2fZZNTB KvXsSW7FBbklHn705WPBSREA/L68y88Nvx7ll9ET7xhWVzMEfybgcshqlX3T2FPDggIIDuGro0IrliYpi/A/kwrG4abSm8ptyFUqF3W4w59t5Ub80pCEYJ3At4taSAEkYz3iQ8Eunh3//v/ztzUfva6aubay/3HK9na/t/uQiEiymHBgtTtdfjiSlbw== 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: List-Subscribe: List-Unsubscribe: Kumar Kartikeya Dwivedi writes: > On Mon, 18 Aug 2025 at 19:02, Roman Gushchin wrote: >> >> Implement a pseudo-realistic test for the OOM handling >> functionality. >> >> The OOM handling policy which is implemented in bpf is to >> kill all tasks belonging to the biggest leaf cgroup, which >> doesn't contain unkillable tasks (tasks with oom_score_adj >> set to -1000). Pagecache size is excluded from the accounting. >> >> The test creates a hierarchy of memory cgroups, causes an >> OOM at the top level, checks that the expected process will be >> killed and checks memcg's oom statistics. >> >> Signed-off-by: Roman Gushchin >> --- >> [...] >> + >> +/* >> + * Find the largest leaf cgroup (ignoring page cache) without unkillable tasks >> + * and kill all belonging tasks. >> + */ >> +SEC("struct_ops.s/handle_out_of_memory") >> +int BPF_PROG(test_out_of_memory, struct oom_control *oc) >> +{ >> + struct task_struct *task; >> + struct mem_cgroup *root_memcg = oc->memcg; >> + struct mem_cgroup *memcg, *victim = NULL; >> + struct cgroup_subsys_state *css_pos; >> + unsigned long usage, max_usage = 0; >> + unsigned long pagecache = 0; >> + int ret = 0; >> + >> + if (root_memcg) >> + root_memcg = bpf_get_mem_cgroup(&root_memcg->css); >> + else >> + root_memcg = bpf_get_root_mem_cgroup(); >> + >> + if (!root_memcg) >> + return 0; >> + >> + bpf_rcu_read_lock(); >> + bpf_for_each(css, css_pos, &root_memcg->css, BPF_CGROUP_ITER_DESCENDANTS_POST) { >> + if (css_pos->cgroup->nr_descendants + css_pos->cgroup->nr_dying_descendants) >> + continue; >> + >> + memcg = bpf_get_mem_cgroup(css_pos); >> + if (!memcg) >> + continue; >> + >> + usage = bpf_mem_cgroup_usage(memcg); >> + pagecache = bpf_mem_cgroup_page_state(memcg, NR_FILE_PAGES); >> + >> + if (usage > pagecache) >> + usage -= pagecache; >> + else >> + usage = 0; >> + >> + if ((usage > max_usage) && mem_cgroup_killable(memcg)) { >> + max_usage = usage; >> + if (victim) >> + bpf_put_mem_cgroup(victim); >> + victim = bpf_get_mem_cgroup(&memcg->css); >> + } >> + >> + bpf_put_mem_cgroup(memcg); >> + } >> + bpf_rcu_read_unlock(); >> + >> + if (!victim) >> + goto exit; >> + >> + bpf_for_each(css_task, task, &victim->css, CSS_TASK_ITER_PROCS) { >> + struct task_struct *t = bpf_task_acquire(task); >> + >> + if (t) { >> + if (!bpf_task_is_oom_victim(task)) >> + bpf_oom_kill_process(oc, task, "bpf oom test"); > > Is there a scenario where we want to invoke bpf_oom_kill_process when > the task is not an oom victim? Not really, but... > Would it be better to subsume this check in the kfunc itself? bpf_task_is_oom_victim() is useful by itself, because if we see a task which is about to be killed, we can likely simple bail out. Let me adjust the test to reflect it.