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 X-Spam-Level: X-Spam-Status: No, score=-8.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 907C9C4360F for ; Fri, 22 Mar 2019 16:03:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 56DDE21900 for ; Fri, 22 Mar 2019 16:03:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chrisdown.name header.i=@chrisdown.name header.b="tD7uE265" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729406AbfCVQDM (ORCPT ); Fri, 22 Mar 2019 12:03:12 -0400 Received: from mail-ed1-f65.google.com ([209.85.208.65]:37763 "EHLO mail-ed1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727518AbfCVQDL (ORCPT ); Fri, 22 Mar 2019 12:03:11 -0400 Received: by mail-ed1-f65.google.com with SMTP id v21so2128199edq.4 for ; Fri, 22 Mar 2019 09:03:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chrisdown.name; s=google; h=date:from:to:cc:subject:message-id:mime-version:content-disposition :in-reply-to:user-agent; bh=llWT3yfNF6jjiDDuWqUaQk5Aa1IzzqftBcYhMCzXqdY=; b=tD7uE265+W48OxBiTjtpQvC9y0iyIRD1RcUxMjqRYm5ahtZz81j4bR9XG+i5AohMT2 Y0cZ9DlN+aM2V6OpqJq8vRKtlqrDEFFJH+tJF26iWdy/IUzgxhGdrDW6ASalXpEXoTa0 qx8oepEaq5xyJ71YHl+MLCV9qRzV3BtBifEq4= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:mime-version :content-disposition:in-reply-to:user-agent; bh=llWT3yfNF6jjiDDuWqUaQk5Aa1IzzqftBcYhMCzXqdY=; b=FcibogJWmoZX6uCjqyhqISZPlIZCr825EpuMJZkxrODBb0ju4MEpo2+O9HP2uyZnZv nz4DJr7z9e9PKxxQ7TLUwjLeRkFHtPzUWoLgKF7t5cHMivvKtHempgBcCSNyjmRkMK82 AcrYOr5jb+NVaTjhVliG2toVAoiMR+14YSm0IyTaEkJcEl787ZhqEteXnyGeXSbcWoOx dc3gyEOfjILmPQnmf9uD1m8dr+vZ8RqFjJMrih8XkNX4ZKR/Jz6oOiaIe1oYUF0rZprF P71Kso9xmo3Gko3YsH12pR35EYFMKJjI6Px732qT8Qx0XnH8p9/9oq3H+PEQSNXBNmd1 MfCg== X-Gm-Message-State: APjAAAU2jLEVS7yZdUWXqVGvfLyQV/bRR4RYmH4EuB6QeQd8qBY+nFvg x1xIaXbSARI1g7kq//3Ladrv0g== X-Google-Smtp-Source: APXvYqyHVjVqSil5Q5EfmazBYeq+omgBC5QZuiTTH4GmJq/eSHZ/a7FXQgdr0seZXVNUZKbY1dqNBg== X-Received: by 2002:a50:ad58:: with SMTP id z24mr6955941edc.75.1553270588939; Fri, 22 Mar 2019 09:03:08 -0700 (PDT) Received: from localhost ([2620:10d:c092:200::1:a21b]) by smtp.gmail.com with ESMTPSA id b26sm1758395ejv.21.2019.03.22.09.03.07 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Fri, 22 Mar 2019 09:03:08 -0700 (PDT) Date: Fri, 22 Mar 2019 16:03:07 +0000 From: Chris Down To: Andrew Morton Cc: Johannes Weiner , Michal Hocko , Tejun Heo , Roman Gushchin , Dennis Zhou , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, kernel-team@fb.com Subject: [PATCH REBASED] mm, memcg: Make scan aggression always exclude protection Message-ID: <20190322160307.GA3316@chrisdown.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190228213050.GA28211@chrisdown.name> User-Agent: Mutt/1.11.4 (2019-03-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This patch is an incremental improvement on the existing memory.{low,min} relative reclaim work to base its scan pressure calculations on how much protection is available compared to the current usage, rather than how much the current usage is over some protection threshold. Previously the way that memory.low protection works is that if you are 50% over a certain baseline, you get 50% of your normal scan pressure. This is certainly better than the previous cliff-edge behaviour, but it can be improved even further by always considering memory under the currently enforced protection threshold to be out of bounds. This means that we can set relatively low memory.low thresholds for variable or bursty workloads while still getting a reasonable level of protection, whereas with the previous version we may still trivially hit the 100% clamp. The previous 100% clamp is also somewhat arbitrary, whereas this one is more concretely based on the currently enforced protection threshold, which is likely easier to reason about. There is also a subtle issue with the way that proportional reclaim worked previously -- it promotes having no memory.low, since it makes pressure higher during low reclaim. This happens because we base our scan pressure modulation on how far memory.current is between memory.min and memory.low, but if memory.low is unset, we only use the overage method. In most cromulent configurations, this then means that we end up with *more* pressure than with no memory.low at all when we're in low reclaim, which is not really very usable or expected. With this patch, memory.low and memory.min affect reclaim pressure in a more understandable and composable way. For example, from a user standpoint, "protected" memory now remains untouchable from a reclaim aggression standpoint, and users can also have more confidence that bursty workloads will still receive some amount of guaranteed protection. Signed-off-by: Chris Down Reviewed-by: Roman Gushchin Cc: Johannes Weiner Cc: Andrew Morton Cc: Michal Hocko Cc: Tejun Heo Cc: Roman Gushchin Cc: Dennis Zhou Cc: linux-kernel@vger.kernel.org Cc: cgroups@vger.kernel.org Cc: linux-mm@kvack.org Cc: kernel-team@fb.com --- include/linux/memcontrol.h | 25 ++++++++-------- mm/vmscan.c | 61 +++++++++++++------------------------- 2 files changed, 32 insertions(+), 54 deletions(-) No functional changes, just rebased. diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index b226c4bafc93..799de23edfb7 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -333,17 +333,17 @@ static inline bool mem_cgroup_disabled(void) return !cgroup_subsys_enabled(memory_cgrp_subsys); } -static inline void mem_cgroup_protection(struct mem_cgroup *memcg, - unsigned long *min, unsigned long *low) +static inline unsigned long mem_cgroup_protection(struct mem_cgroup *memcg, + bool in_low_reclaim) { - if (mem_cgroup_disabled()) { - *min = 0; - *low = 0; - return; - } + if (mem_cgroup_disabled()) + return 0; + + if (in_low_reclaim) + return READ_ONCE(memcg->memory.emin); - *min = READ_ONCE(memcg->memory.emin); - *low = READ_ONCE(memcg->memory.elow); + return max(READ_ONCE(memcg->memory.emin), + READ_ONCE(memcg->memory.elow)); } enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *root, @@ -845,11 +845,10 @@ static inline void memcg_memory_event_mm(struct mm_struct *mm, { } -static inline void mem_cgroup_protection(struct mem_cgroup *memcg, - unsigned long *min, unsigned long *low) +static inline unsigned long mem_cgroup_protection(struct mem_cgroup *memcg, + bool in_low_reclaim) { - *min = 0; - *low = 0; + return 0; } static inline enum mem_cgroup_protection mem_cgroup_protected( diff --git a/mm/vmscan.c b/mm/vmscan.c index f6b9b45f731d..d5daa224364d 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2374,12 +2374,13 @@ static void get_scan_count(struct lruvec *lruvec, struct mem_cgroup *memcg, int file = is_file_lru(lru); unsigned long lruvec_size; unsigned long scan; - unsigned long min, low; + unsigned long protection; lruvec_size = lruvec_lru_size(lruvec, lru, sc->reclaim_idx); - mem_cgroup_protection(memcg, &min, &low); + protection = mem_cgroup_protection(memcg, + sc->memcg_low_reclaim); - if (min || low) { + if (protection) { /* * Scale a cgroup's reclaim pressure by proportioning * its current usage to its memory.low or memory.min @@ -2392,13 +2393,10 @@ static void get_scan_count(struct lruvec *lruvec, struct mem_cgroup *memcg, * setting extremely liberal protection thresholds. It * also means we simply get no protection at all if we * set it too low, which is not ideal. - */ - unsigned long cgroup_size = mem_cgroup_size(memcg); - - /* - * If there is any protection in place, we adjust scan - * pressure in proportion to how much a group's current - * usage exceeds that, in percent. + * + * If there is any protection in place, we reduce scan + * pressure by how much of the total memory used is + * within protection thresholds. * * There is one special case: in the first reclaim pass, * we skip over all groups that are within their low @@ -2408,43 +2406,24 @@ static void get_scan_count(struct lruvec *lruvec, struct mem_cgroup *memcg, * ideally want to honor how well-behaved groups are in * that case instead of simply punishing them all * equally. As such, we reclaim them based on how much - * of their best-effort protection they are using. Usage - * below memory.min is excluded from consideration when - * calculating utilisation, as it isn't ever - * reclaimable, so it might as well not exist for our - * purposes. + * memory they are using, reducing the scan pressure + * again by how much of the total memory used is under + * hard protection. */ - if (sc->memcg_low_reclaim && low > min) { - /* - * Reclaim according to utilisation between min - * and low - */ - scan = lruvec_size * (cgroup_size - min) / - (low - min); - } else { - /* Reclaim according to protection overage */ - scan = lruvec_size * cgroup_size / - max(min, low) - lruvec_size; - } + unsigned long cgroup_size = mem_cgroup_size(memcg); + + /* Avoid TOCTOU with earlier protection check */ + cgroup_size = max(cgroup_size, protection); + + scan = lruvec_size - lruvec_size * protection / + cgroup_size; /* - * Don't allow the scan target to exceed the lruvec - * size, which otherwise could happen if we have >200% - * overage in the normal case, or >100% overage when - * sc->memcg_low_reclaim is set. - * - * This is important because other cgroups without - * memory.low have their scan target initially set to - * their lruvec size, so allowing values >100% of the - * lruvec size here could result in penalising cgroups - * with memory.low set even *more* than their peers in - * some cases in the case of large overages. - * - * Also, minimally target SWAP_CLUSTER_MAX pages to keep + * Minimally target SWAP_CLUSTER_MAX pages to keep * reclaim moving forwards, avoiding decremeting * sc->priority further than desirable. */ - scan = clamp(scan, SWAP_CLUSTER_MAX, lruvec_size); + scan = max(scan, SWAP_CLUSTER_MAX); } else { scan = lruvec_size; } -- 2.21.0