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 898AEC433F5 for ; Fri, 11 Feb 2022 22:35:54 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8F41E6B007D; Fri, 11 Feb 2022 17:35:49 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 6E3046B007E; Fri, 11 Feb 2022 17:35:49 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4E0498D0002; Fri, 11 Feb 2022 17:35:49 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0066.hostedemail.com [216.40.44.66]) by kanga.kvack.org (Postfix) with ESMTP id 1FF3E8D0002 for ; Fri, 11 Feb 2022 17:35:49 -0500 (EST) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id D381F9A7ED for ; Fri, 11 Feb 2022 22:35:48 +0000 (UTC) X-FDA: 79131957576.25.76008E5 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by imf15.hostedemail.com (Postfix) with ESMTP id 44394A0008 for ; Fri, 11 Feb 2022 22:35:48 +0000 (UTC) From: Sebastian Andrzej Siewior DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1644618946; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=CtnQ/jKOXRc8a6xZ9GWxhxNQwNrZxILRPNGj9AW3VcA=; b=u3z2mDV13XSe3El21I9eb7YJRguX0MUChuJJQo/qnzBwJVQpw96QsMT3S+oMag/Fy7DQDN 72cU/BtFmL31A7qiBLnRjiBmBSMrAlELLsJKhcnQNuftN94Yw+CaH5V7eiqCIj5wEc8f4t 3nTjNzupD+LTD8QqZYCAkZrHMvEiZRAra59rjB6oOFrLxbixh/8Nh7JrbxxL/EE25JRqwU zBZEq074GDaGqEmlbFfdMtcRRuNvF8XcMUOOL23twuArJweICfJWbucS8y6DzaOSYGMpUG SDmq6uFjOu38DubfeMO497hVqaxz09zihzbjcuCiv12NXaDvM/ELZn9JRMxkng== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1644618946; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=CtnQ/jKOXRc8a6xZ9GWxhxNQwNrZxILRPNGj9AW3VcA=; b=kYfjRvHr7iEaLYuLlch0R2uJnpiRDfqHj+EEtXkzQqM8ln9dH31I6RKYkh53yy+EPI0nMa tKE8I6rEVltBIdCA== To: cgroups@vger.kernel.org, linux-mm@kvack.org Cc: Andrew Morton , Johannes Weiner , Michal Hocko , =?UTF-8?q?Michal=20Koutn=C3=BD?= , Peter Zijlstra , Thomas Gleixner , Vladimir Davydov , Waiman Long , Sebastian Andrzej Siewior Subject: [PATCH v2 2/4] mm/memcg: Disable threshold event handlers on PREEMPT_RT Date: Fri, 11 Feb 2022 23:35:35 +0100 Message-Id: <20220211223537.2175879-3-bigeasy@linutronix.de> In-Reply-To: <20220211223537.2175879-1-bigeasy@linutronix.de> References: <20220211223537.2175879-1-bigeasy@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 44394A0008 X-Stat-Signature: 691rrf89bwwmr8nx77bb17d5dxwqzdg5 Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=linutronix.de header.s=2020 header.b=u3z2mDV1; dkim=pass header.d=linutronix.de header.s=2020e header.b=kYfjRvHr; spf=pass (imf15.hostedemail.com: domain of bigeasy@linutronix.de designates 193.142.43.55 as permitted sender) smtp.mailfrom=bigeasy@linutronix.de; dmarc=pass (policy=none) header.from=linutronix.de X-Rspam-User: X-HE-Tag: 1644618948-783654 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: During the integration of PREEMPT_RT support, the code flow around memcg_check_events() resulted in `twisted code'. Moving the code around and avoiding then would then lead to an additional local-irq-save section within memcg_check_events(). While looking better, it adds a local-irq-save section to code flow which is usually within an local-irq-off block on non-PREEMPT_RT configurations. The threshold event handler is a deprecated memcg v1 feature. Instead of trying to get it to work under PREEMPT_RT just disable it. There should be no users on PREEMPT_RT. From that perspective it makes even less sense to get it to work under PREEMPT_RT while having zero users. Make memory.soft_limit_in_bytes and cgroup.event_control return -EOPNOTSUPP on PREEMPT_RT. Make an empty memcg_check_events() and memcg_write_event_control() which return only -EOPNOTSUPP on PREEMPT_RT. Document that the two knobs are disabled on PREEMPT_RT. Suggested-by: Michal Hocko Suggested-by: Michal Koutn=C3=BD Signed-off-by: Sebastian Andrzej Siewior --- Documentation/admin-guide/cgroup-v1/memory.rst | 2 ++ mm/memcontrol.c | 14 ++++++++++++-- 2 files changed, 14 insertions(+), 2 deletions(-) diff --git a/Documentation/admin-guide/cgroup-v1/memory.rst b/Documentation= /admin-guide/cgroup-v1/memory.rst index faac50149a222..2cc502a75ef64 100644 --- a/Documentation/admin-guide/cgroup-v1/memory.rst +++ b/Documentation/admin-guide/cgroup-v1/memory.rst @@ -64,6 +64,7 @@ Brief summary of control files. threads cgroup.procs show list of processes cgroup.event_control an interface for event_fd() + This knob is not available on CONFIG_PREEMPT_RT systems. memory.usage_in_bytes show current usage for memory (See 5.5 for details) memory.memsw.usage_in_bytes show current usage for memory+Swap @@ -75,6 +76,7 @@ Brief summary of control files. memory.max_usage_in_bytes show max memory usage recorded memory.memsw.max_usage_in_bytes show max memory+Swap usage recorded memory.soft_limit_in_bytes set/show soft limit of memory usage + This knob is not available on CONFIG_PREEMPT_RT systems. memory.stat show various statistics memory.use_hierarchy set/show hierarchical account enabled This knob is deprecated and shouldn't= be diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 4b1572ae990d8..c1caa662946dc 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -858,6 +858,9 @@ static bool mem_cgroup_event_ratelimit(struct mem_cgrou= p *memcg, */ static void memcg_check_events(struct mem_cgroup *memcg, int nid) { + if (IS_ENABLED(CONFIG_PREEMPT_RT)) + return; + /* threshold event is triggered in finer grain than soft limit */ if (unlikely(mem_cgroup_event_ratelimit(memcg, MEM_CGROUP_TARGET_THRESH))) { @@ -3724,8 +3727,12 @@ static ssize_t mem_cgroup_write(struct kernfs_open_f= ile *of, } break; case RES_SOFT_LIMIT: - memcg->soft_limit =3D nr_pages; - ret =3D 0; + if (IS_ENABLED(CONFIG_PREEMPT_RT)) { + ret =3D -EOPNOTSUPP; + } else { + memcg->soft_limit =3D nr_pages; + ret =3D 0; + } break; } return ret ?: nbytes; @@ -4701,6 +4708,9 @@ static ssize_t memcg_write_event_control(struct kernf= s_open_file *of, char *endp; int ret; =20 + if (IS_ENABLED(CONFIG_PREEMPT_RT)) + return -EOPNOTSUPP; + buf =3D strstrip(buf); =20 efd =3D simple_strtoul(buf, &endp, 10); --=20 2.34.1