From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DEB096453 for ; Tue, 22 Mar 2022 21:40:38 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A6819C340EE; Tue, 22 Mar 2022 21:40:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1647985238; bh=KT+NPJJrwHEXCM5HymWRmRika9piNngSILhdKqRhzN0=; h=Date:To:From:In-Reply-To:Subject:From; b=whkXKU+SAG5J70E60H3TsNvgfkOJ4NZYn9D7GzUHSVtsnSbCrk1US5CPtfSwvYBhY IXJIhUh/Lb1VzNCkcea9Wfn8MHe7QVJztlo+e/ympg0VPxMam9W+b+HVBjUX1knvod n9tJonwap5i87Q86jum4lPWiIqnk7doWtl9xhfDo= Date: Tue, 22 Mar 2022 14:40:38 -0700 To: vdavydov.dev@gmail.com,tglx@linutronix.de,shakeelb@google.com,peterz@infradead.org,oliver.sang@intel.com,mkoutny@suse.com,mhocko@suse.com,mhocko@kernel.org,longman@redhat.com,hannes@cmpxchg.org,guro@fb.com,bigeasy@linutronix.de,akpm@linux-foundation.org,patches@lists.linux.dev,linux-mm@kvack.org,mm-commits@vger.kernel.org,torvalds@linux-foundation.org,akpm@linux-foundation.org From: Andrew Morton In-Reply-To: <20220322143803.04a5e59a07e48284f196a2f9@linux-foundation.org> Subject: [patch 042/227] mm/memcg: disable threshold event handlers on PREEMPT_RT Message-Id: <20220322214038.A6819C340EE@smtp.kernel.org> Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: From: Sebastian Andrzej Siewior Subject: mm/memcg: disable threshold event handlers on PREEMPT_RT 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. Link: https://lkml.kernel.org/r/20220226204144.1008339-3-bigeasy@linutronix.de 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 Cc: kernel test robot Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Vladimir Davydov Cc: Waiman Long Signed-off-by: Andrew Morton --- Documentation/admin-guide/cgroup-v1/memory.rst | 2 ++ mm/memcontrol.c | 14 ++++++++++++-- 2 files changed, 14 insertions(+), 2 deletions(-) --- a/Documentation/admin-guide/cgroup-v1/memory.rst~mm-memcg-disable-threshold-event-handlers-on-preempt_rt +++ a/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 --- a/mm/memcontrol.c~mm-memcg-disable-threshold-event-handlers-on-preempt_rt +++ a/mm/memcontrol.c @@ -858,6 +858,9 @@ static bool mem_cgroup_event_ratelimit(s */ 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 k } 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 char *endp; int ret; + if (IS_ENABLED(CONFIG_PREEMPT_RT)) + return -EOPNOTSUPP; + buf = strstrip(buf); efd = simple_strtoul(buf, &endp, 10); _ 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4FF78C433EF for ; Tue, 22 Mar 2022 21:40:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235932AbiCVVmU (ORCPT ); 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b=whkXKU+SAG5J70E60H3TsNvgfkOJ4NZYn9D7GzUHSVtsnSbCrk1US5CPtfSwvYBhY IXJIhUh/Lb1VzNCkcea9Wfn8MHe7QVJztlo+e/ympg0VPxMam9W+b+HVBjUX1knvod n9tJonwap5i87Q86jum4lPWiIqnk7doWtl9xhfDo= Date: Tue, 22 Mar 2022 14:40:38 -0700 To: vdavydov.dev@gmail.com, tglx@linutronix.de, shakeelb@google.com, peterz@infradead.org, oliver.sang@intel.com, mkoutny@suse.com, mhocko@suse.com, mhocko@kernel.org, longman@redhat.com, hannes@cmpxchg.org, guro@fb.com, bigeasy@linutronix.de, akpm@linux-foundation.org, patches@lists.linux.dev, linux-mm@kvack.org, mm-commits@vger.kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org From: Andrew Morton In-Reply-To: <20220322143803.04a5e59a07e48284f196a2f9@linux-foundation.org> Subject: [patch 042/227] mm/memcg: disable threshold event handlers on PREEMPT_RT Message-Id: <20220322214038.A6819C340EE@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Sebastian Andrzej Siewior Subject: mm/memcg: disable threshold event handlers on PREEMPT_RT 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. Link: https://lkml.kernel.org/r/20220226204144.1008339-3-bigeasy@linutronix.de 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 Cc: kernel test robot Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Vladimir Davydov Cc: Waiman Long Signed-off-by: Andrew Morton --- Documentation/admin-guide/cgroup-v1/memory.rst | 2 ++ mm/memcontrol.c | 14 ++++++++++++-- 2 files changed, 14 insertions(+), 2 deletions(-) --- a/Documentation/admin-guide/cgroup-v1/memory.rst~mm-memcg-disable-threshold-event-handlers-on-preempt_rt +++ a/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 --- a/mm/memcontrol.c~mm-memcg-disable-threshold-event-handlers-on-preempt_rt +++ a/mm/memcontrol.c @@ -858,6 +858,9 @@ static bool mem_cgroup_event_ratelimit(s */ 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 k } 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 char *endp; int ret; + if (IS_ENABLED(CONFIG_PREEMPT_RT)) + return -EOPNOTSUPP; + buf = strstrip(buf); efd = simple_strtoul(buf, &endp, 10); _