From patchwork Thu Mar 31 08:41:51 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yosry Ahmed X-Patchwork-Id: 12796859 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 A2837C433EF for ; Thu, 31 Mar 2022 08:42:00 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 191E46B0072; Thu, 31 Mar 2022 04:42:00 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 141F76B0073; Thu, 31 Mar 2022 04:42:00 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F24EF6B0074; Thu, 31 Mar 2022 04:41:59 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0163.hostedemail.com [216.40.44.163]) by kanga.kvack.org (Postfix) with ESMTP id E39C56B0072 for ; Thu, 31 Mar 2022 04:41:59 -0400 (EDT) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 99DF2182DD9F1 for ; Thu, 31 Mar 2022 08:41:59 +0000 (UTC) X-FDA: 79304038758.22.D02B5AE Received: from mail-pj1-f73.google.com (mail-pj1-f73.google.com [209.85.216.73]) by imf01.hostedemail.com (Postfix) with ESMTP id DF00940013 for ; Thu, 31 Mar 2022 08:41:58 +0000 (UTC) Received: by mail-pj1-f73.google.com with SMTP id ob7-20020a17090b390700b001c692ec6de4so1518144pjb.7 for ; Thu, 31 Mar 2022 01:41:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:message-id:mime-version:subject:from:to:cc; bh=dJR2UF7wpFVBWBgJ9O65H/XFooxj9+B28f9BB5t99yU=; b=Uw8yGthrisayNeORy4SJ0M18Sm95p4V7hygwzdHg6T2IFLejLl/kkfy77e3J2MZghG QIAja02cdJ6iGsot5VfVtPIlTLtEHl8iJJz6E3NX8tpU6bejFYq4Fz5wQ8MAKSrbfY92 O1TrJHO1sbNGFv3kKywVlM1Gj4SviJ2ra9aY43blbOD1K+xzRSX9Y7n5FfEtLw/qOMbt Qq0KyErJpuLjD3ZLTF8tHweLvo2o96Q6o18wIaXW2wvG9b4yUYwLgXPiq1XRRf+OdWJ1 gIQ5YW1B/+3pIWYyO8ZH0YxFklgV/aPPnq80r9V1XXbgyj2wkf9ekrYoqSRcvCyLWnBh CAeQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=dJR2UF7wpFVBWBgJ9O65H/XFooxj9+B28f9BB5t99yU=; b=WMLsUgmGEVgCRXb71c6+S5+csetJnqEdkErWSzLZDpQwc4UhQkIoZLmTBeB6Sl6R2l mbedPFfE7AgXyb/obX5xlL6WT9EYBb1C0EUU8gFi5hZA9x9dnKuy5o6YRZDbxVu+NyIk t9BwWUjpfGcEApY8/FagL2J/MlM617pwYigQIjm1WhyL1glkFZnx9bnmc5fi4SfF2Xbp 8aJUjB6AH8cn4ejVqkbmRzzYW2md0X3+7aH8t5RH6TK4IyiqjEni30huYu4Rxy6Uw5Pa eDCpu276qk/fMeQmtATxIfImDmIBIoq33Ob5+mv36noPP0wxsVrXJ0Qu7C2FdbduN1St gO6A== X-Gm-Message-State: AOAM532O8o6aH/w7Cr/DWsT9WuFNagJg+fNHZATW6RuCC8tB2FyljrkD AiMaVhlj8Tk0o7/ugcPhHqktF4R6KhAWxlh8 X-Google-Smtp-Source: ABdhPJx+5hJ7dlHIY+PAfuvlN3r6vNUT2fJuTbeGOFggvCUmI3ysuol8PaUWv+9qjjLMsEw0140rcQDfL3zk+Hcq X-Received: from yosry.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:2327]) (user=yosryahmed job=sendgmr) by 2002:a17:902:da88:b0:156:2b13:81c5 with SMTP id j8-20020a170902da8800b001562b1381c5mr4282286plx.138.1648716117730; Thu, 31 Mar 2022 01:41:57 -0700 (PDT) Date: Thu, 31 Mar 2022 08:41:51 +0000 Message-Id: <20220331084151.2600229-1-yosryahmed@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.35.1.1021.g381101b075-goog Subject: [PATCH resend] memcg: introduce per-memcg reclaim interface From: Yosry Ahmed To: Johannes Weiner , Michal Hocko , Shakeel Butt , Andrew Morton , David Rientjes Cc: Tejun Heo , Zefan Li , Roman Gushchin , cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Jonathan Corbet , Yu Zhao , Dave Hansen , Wei Xu , Greg Thelen , Yosry Ahmed X-Stat-Signature: 51enrsxic57sit16sifsifajktt4sn5t Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=Uw8yGthr; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf01.hostedemail.com: domain of 3VWlFYgoKCFYMCGFMy5A214CC492.0CA96BIL-AA8Jy08.CF4@flex--yosryahmed.bounces.google.com designates 209.85.216.73 as permitted sender) smtp.mailfrom=3VWlFYgoKCFYMCGFMy5A214CC492.0CA96BIL-AA8Jy08.CF4@flex--yosryahmed.bounces.google.com X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: DF00940013 X-HE-Tag: 1648716118-325780 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: From: Shakeel Butt Introduce an memcg interface to trigger memory reclaim on a memory cgroup. Use case: Proactive Reclaim --------------------------- A userspace proactive reclaimer can continuously probe the memcg to reclaim a small amount of memory. This gives more accurate and up-to-date workingset estimation as the LRUs are continuously sorted and can potentially provide more deterministic memory overcommit behavior. The memory overcommit controller can provide more proactive response to the changing behavior of the running applications instead of being reactive. A userspace reclaimer's purpose in this case is not a complete replacement for kswapd or direct reclaim, it is to proactively identify memory savings opportunities and reclaim some amount of cold pages set by the policy to free up the memory for more demanding jobs or scheduling new jobs. A user space proactive reclaimer is used in Google data centers. Additionally, Meta's TMO paper recently referenced a very similar interface used for user space proactive reclaim: https://dl.acm.org/doi/pdf/10.1145/3503222.3507731 Benefits of a user space reclaimer: ----------------------------------- 1) More flexible on who should be charged for the cpu of the memory reclaim. For proactive reclaim, it makes more sense to be centralized. 2) More flexible on dedicating the resources (like cpu). The memory overcommit controller can balance the cost between the cpu usage and the memory reclaimed. 3) Provides a way to the applications to keep their LRUs sorted, so, under memory pressure better reclaim candidates are selected. This also gives more accurate and uptodate notion of working set for an application. Why memory.high is not enough? ------------------------------ - memory.high can be used to trigger reclaim in a memcg and can potentially be used for proactive reclaim. However there is a big downside in using memory.high. It can potentially introduce high reclaim stalls in the target application as the allocations from the processes or the threads of the application can hit the temporary memory.high limit. - Userspace proactive reclaimers usually use feedback loops to decide how much memory to proactively reclaim from a workload. The metrics used for this are usually either refaults or PSI, and these metrics will become messy if the application gets throttled by hitting the high limit. - memory.high is a stateful interface, if the userspace proactive reclaimer crashes for any reason while triggering reclaim it can leave the application in a bad state. - If a workload is rapidly expanding, setting memory.high to proactively reclaim memory can result in actually reclaiming more memory than intended. The benefits of such interface and shortcomings of existing interface were further discussed in this RFC thread: https://lore.kernel.org/linux-mm/5df21376-7dd1-bf81-8414-32a73cea45dd@google.com/ Interface: ---------- Introducing a very simple memcg interface 'echo 10M > memory.reclaim' to trigger reclaim in the target memory cgroup. Possible Extensions: -------------------- - This interface can be extended with an additional parameter or flags to allow specifying one or more types of memory to reclaim from (e.g. file, anon, ..). - The interface can also be extended with a node mask to reclaim from specific nodes. This has use cases for reclaim-based demotion in memory tiering systens. - A similar per-node interface can also be added to support proactive reclaim and reclaim-based demotion in systems without memcg. For now, let's keep things simple by adding the basic functionality. [yosryahmed@google.com: refreshed to current master, updated commit message based on recent discussions and use cases] Signed-off-by: Shakeel Butt Signed-off-by: Yosry Ahmed Acked-by: Johannes Weiner Acked-by: Michal Hocko --- Documentation/admin-guide/cgroup-v2.rst | 9 ++++++ mm/memcontrol.c | 37 +++++++++++++++++++++++++ 2 files changed, 46 insertions(+) diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst index 69d7a6983f78..925aaabb2247 100644 --- a/Documentation/admin-guide/cgroup-v2.rst +++ b/Documentation/admin-guide/cgroup-v2.rst @@ -1208,6 +1208,15 @@ PAGE_SIZE multiple when read back. high limit is used and monitored properly, this limit's utility is limited to providing the final safety net. + memory.reclaim + A write-only file which exists on non-root cgroups. + + This is a simple interface to trigger memory reclaim in the + target cgroup. Write the number of bytes to reclaim to this + file and the kernel will try to reclaim that much memory. + Please note that the kernel can over or under reclaim from + the target cgroup. + memory.oom.group A read-write single value file which exists on non-root cgroups. The default value is "0". diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 725f76723220..994849fab7df 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -6355,6 +6355,38 @@ static ssize_t memory_oom_group_write(struct kernfs_open_file *of, return nbytes; } +static ssize_t memory_reclaim(struct kernfs_open_file *of, char *buf, + size_t nbytes, loff_t off) +{ + struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of)); + unsigned int nr_retries = MAX_RECLAIM_RETRIES; + unsigned long nr_to_reclaim, nr_reclaimed = 0; + int err; + + buf = strstrip(buf); + err = page_counter_memparse(buf, "", &nr_to_reclaim); + if (err) + return err; + + while (nr_reclaimed < nr_to_reclaim) { + unsigned long reclaimed; + + if (signal_pending(current)) + break; + + reclaimed = try_to_free_mem_cgroup_pages(memcg, + nr_to_reclaim - nr_reclaimed, + GFP_KERNEL, true); + + if (!reclaimed && !nr_retries--) + break; + + nr_reclaimed += reclaimed; + } + + return nbytes; +} + static struct cftype memory_files[] = { { .name = "current", @@ -6413,6 +6445,11 @@ static struct cftype memory_files[] = { .seq_show = memory_oom_group_show, .write = memory_oom_group_write, }, + { + .name = "reclaim", + .flags = CFTYPE_NOT_ON_ROOT | CFTYPE_NS_DELEGATABLE, + .write = memory_reclaim, + }, { } /* terminate */ };