From patchwork Thu Feb 17 09:47:59 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Sebastian Andrzej Siewior X-Patchwork-Id: 12749687 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 66B9EC433FE for ; Thu, 17 Feb 2022 09:48:12 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 4F3266B0078; Thu, 17 Feb 2022 04:48:10 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 404956B007B; Thu, 17 Feb 2022 04:48:10 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 22F076B007D; Thu, 17 Feb 2022 04:48:10 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0068.hostedemail.com [216.40.44.68]) by kanga.kvack.org (Postfix) with ESMTP id 122626B0078 for ; Thu, 17 Feb 2022 04:48:10 -0500 (EST) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id B15DE8249980 for ; Thu, 17 Feb 2022 09:48:09 +0000 (UTC) X-FDA: 79151795898.27.3614AF9 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by imf05.hostedemail.com (Postfix) with ESMTP id 0D1A110000E for ; Thu, 17 Feb 2022 09:48:08 +0000 (UTC) From: Sebastian Andrzej Siewior DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1645091287; 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=+YK9BAbzRHLQMq1juWmxjiOoknuxlRDdzwwjsluBi8c=; b=q8lRQHoGi2PQHO36VPEbo4ntN5HOPDTRaTDTHZnQh5sMU4uEMIvJd7E3AhwIhpuW/g8JPp v23JGi57QjBX5HgSJiYtXmp5tK9CtXfpNyFu76Vppiecl7SLEmUxVS/s/2KlD84KaSaJVP B/EPT6TlKbO7rbhe6nlVo2oUsO6eVaTqBJrd5HW9Gpp2n17S3v8sfFnqJDL7OHEtcr3jK9 A4/7Nzi1K/KLUrjWEVgqeiBceQ8SoDJheW0pQvdjThKBuRoACRCj5ZMQ40vXoC/E64V3jw eqOIduXysDAZ5LjmpE+HvkRARbKEDghL0GNXOikP/AuHYUnrz7RXRshdjmwlag== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1645091287; 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=+YK9BAbzRHLQMq1juWmxjiOoknuxlRDdzwwjsluBi8c=; b=B9qWJiYyQi0ZyyZWOQpXIjJpMplXI6p4y/mwX0DdmDiNPfy4Ftmc0xHh06mvYz5t0690c5 poc62RSFgWO1FsCQ== To: cgroups@vger.kernel.org, linux-mm@kvack.org Cc: Andrew Morton , Johannes Weiner , Michal Hocko , =?utf-8?q?Michal_Koutn=C3=BD?= , Peter Zijlstra , Thomas Gleixner , Vladimir Davydov , Waiman Long , Sebastian Andrzej Siewior , Roman Gushchin Subject: [PATCH v3 2/5] mm/memcg: Disable threshold event handlers on PREEMPT_RT Date: Thu, 17 Feb 2022 10:47:59 +0100 Message-Id: <20220217094802.3644569-3-bigeasy@linutronix.de> In-Reply-To: <20220217094802.3644569-1-bigeasy@linutronix.de> References: <20220217094802.3644569-1-bigeasy@linutronix.de> MIME-Version: 1.0 Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=linutronix.de header.s=2020 header.b=q8lRQHoG; dkim=pass header.d=linutronix.de header.s=2020e header.b=B9qWJiYy; dmarc=pass (policy=none) header.from=linutronix.de; spf=pass (imf05.hostedemail.com: domain of bigeasy@linutronix.de designates 193.142.43.55 as permitted sender) smtp.mailfrom=bigeasy@linutronix.de X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 0D1A110000E X-Stat-Signature: qnt83rhiibaq89b6h5be6nnspcsruk9j X-HE-Tag: 1645091288-649032 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 Koutný Signed-off-by: Sebastian Andrzej Siewior Acked-by: Roman Gushchin Acked-by: Johannes Weiner Reviewed-by: Shakeel Butt Acked-by: Michal Hocko --- 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 8ab2dc75e70ec..0b5117ed2ae08 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -859,6 +859,9 @@ static bool mem_cgroup_event_ratelimit(struct mem_cgroup *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))) { @@ -3731,8 +3734,12 @@ static ssize_t mem_cgroup_write(struct kernfs_open_file *of, } break; case RES_SOFT_LIMIT: - memcg->soft_limit = nr_pages; - ret = 0; + if (IS_ENABLED(CONFIG_PREEMPT_RT)) { + ret = -EOPNOTSUPP; + } else { + memcg->soft_limit = nr_pages; + ret = 0; + } break; } return ret ?: nbytes; @@ -4708,6 +4715,9 @@ static ssize_t memcg_write_event_control(struct kernfs_open_file *of, char *endp; int ret; + if (IS_ENABLED(CONFIG_PREEMPT_RT)) + return -EOPNOTSUPP; + buf = strstrip(buf); efd = simple_strtoul(buf, &endp, 10);