From patchwork Mon Jun 17 17:05:42 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jiaqi Yan X-Patchwork-Id: 805814 Received: from mail-yw1-f202.google.com (mail-yw1-f202.google.com [209.85.128.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2A309168486 for ; Mon, 17 Jun 2024 17:05:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718643951; cv=none; b=TNTxS4uo8mGVnQzDJUE7rkntJoqx3Mts6ROpv7N/0KsIbPH/qdCq0uKKi+s5ZakRUvB0oawPUOOi0Flb/jw3T8WEwiYaSf3iVSaCNKfWcJHygQqLck+1FncHlkbKXk/strDn2Cg5ChkOJM8VumrflgVlM7ihYsW82kfVGxU1aec= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718643951; c=relaxed/simple; bh=nrb8VcEEmqzCZY0AyheJ4dwjXJaxNn/pRIAkPqq0mIc=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=CEdR94ug9icxW8sl/11l43g/+ZeVMtodz7g2LxqZmmtUXSWaHKJLR7fNxHCfVEXXTFTth3fEy137ZKuKtr6mriPR7kV50wDXjYhwcHTyxBVRVUDOtKmQ7U/lpT3HXJQOEa9eUjFQCpqP7toEgNpT0UiYHqh/cVA4/zt2eFUjuGY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--jiaqiyan.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=y5Lmtqz/; arc=none smtp.client-ip=209.85.128.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jiaqiyan.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="y5Lmtqz/" Received: by mail-yw1-f202.google.com with SMTP id 00721157ae682-6338f71a577so49192577b3.1 for ; Mon, 17 Jun 2024 10:05:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1718643949; x=1719248749; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=v7FfUmROvXWPzNqZLzmg1Chpa3PlFFTPBJMZ6K8GE4k=; b=y5Lmtqz/4VmSxMQhjd9pv4F7F9RqAMcRLR5JbhOnN32Yr46WlFr52rDqxfplHzsRWl 2r79coUO0Sw9aBZoAIXvWR4QQ1FZyRCmBMJl9GTL/qDOM99TPAjP9YhSkktbxMnNSjk+ TRsRz2dW2j01BWTuykv3JshlpCC8qF7Aq270JjR0F7WoRaCwCx99kczhjWX1tbz8anVH CCsr3xfamYlV/l1ynvvRuW7MnUSUoTscHhDhVt9yXxkYJTeYpAfGNepbPkm+XiQkyp10 5W5SDF6/ty4T1iAMGz52CC19jKKBcR27k02LqeVIP8mu+KLecSVE0tALoLMr3Ew/EtPd /TdQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1718643949; x=1719248749; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=v7FfUmROvXWPzNqZLzmg1Chpa3PlFFTPBJMZ6K8GE4k=; b=Mnl36z2PvFYxA/q6KRMBQw5+Bk2h/QJJ0ixGCtC7DkoR+iX9Xn67lCA127Q7hyfH8m cl4/QuOg6fpsGUy8zIbEE3q3MP+I5WqC44KrFyxc94T1koXDvvcqyUTNyZrVq5BovA7+ CpZgFa+WTDU/7ZuRa+rZ/vMlaizuiIsUJb5c5SgucCUUGgu634/DIZvMN5jHTqYMFGgv j6EZbGpTa6Eza4MFfgy8DVTpVAhy44IYt413Q4pTff8ZyMuQ/JZfGpYEhPOByvYEFaaQ WSSmKqahDovg4Xk/U6h0/O/rMkmshdDsCMHT5aY8k87ePtNBm3dFjA6Fk0eyt+pS2lIc /xQg== X-Forwarded-Encrypted: i=1; AJvYcCWc6y/qt18YZSeIae9PZyuLDejllX+JZ2qfZCupKwBbQTviG+ElMFQG08QdhGQXoc0tyHW0UnWA3QqszIeFe6qhx+6hz24B3ko81AiWV3Od X-Gm-Message-State: AOJu0YwFqrI8RA2ig5zDoxabGSXeq288rFYBeoue4PXAHXNf8n74a8qD ZbwUq4csyE5esvfZ6PqkWoRD/uQJRUZ3ehVH1s/Jk/f9c+OO9d0vwyUCPg2PFfLxXCI6N4W2N8Q XKndBY9JyKQ== X-Google-Smtp-Source: AGHT+IG6R2axixGQhhzTe7v99HTPI+dX+xPnuaKeod6jwj6XeI/di+Vqf4aBYtfcMff+UqyPSeISN4w3QpoWsQ== X-Received: from yjq3.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:272f]) (user=jiaqiyan job=sendgmr) by 2002:a05:690c:4805:b0:631:9b3b:525d with SMTP id 00721157ae682-63222b588bdmr27182107b3.4.1718643949130; Mon, 17 Jun 2024 10:05:49 -0700 (PDT) Date: Mon, 17 Jun 2024 17:05:42 +0000 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.45.2.627.g7a2c4fd464-goog Message-ID: <20240617170545.3820912-1-jiaqiyan@google.com> Subject: [PATCH v3 0/3] Userspace controls soft-offline pages From: Jiaqi Yan To: nao.horiguchi@gmail.com, linmiaohe@huawei.com, jane.chu@oracle.com, ioworker0@gmail.com Cc: muchun.song@linux.dev, akpm@linux-foundation.org, shuah@kernel.org, corbet@lwn.net, osalvador@suse.de, rientjes@google.com, duenwen@google.com, fvdl@google.com, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-doc@vger.kernel.org, Jiaqi Yan Correctable memory errors are very common on servers with large amount of memory, and are corrected by ECC, but with two pain points to users: 1. Correction usually happens on the fly and adds latency overhead 2. Not-fully-proved theory states excessive correctable memory errors can develop into uncorrectable memory error. Soft offline is kernel's additional solution for memory pages having (excessive) corrected memory errors. Impacted page is migrated to healthy page if it is in use, then the original page is discarded for any future use. The actual policy on whether (and when) to soft offline should be maintained by userspace, especially in case of an 1G HugeTLB page. Soft-offline dissolves the HugeTLB page, either in-use or free, into chunks of 4K pages, reducing HugeTLB pool capacity by 1 hugepage. If userspace has not acknowledged such behavior, it may be surprised when later mmap hugepages MAP_FAILED due to lack of hugepages. In case of a transparent hugepage, it will be split into 4K pages as well; userspace will stop enjoying the transparent performance. In addition, discarding the entire 1G HugeTLB page only because of corrected memory errors sounds very costly and kernel better not doing under the hood. But today there are at least 2 such cases: 1. GHES driver sees both GHES_SEV_CORRECTED and CPER_SEC_ERROR_THRESHOLD_EXCEEDED after parsing CPER. 2. RAS Correctable Errors Collector counts correctable errors per PFN and when the counter for a PFN reaches threshold In both cases, userspace has no control of the soft offline performed by kernel's memory failure recovery. This patch series give userspace the control of softofflining any page: kernel only soft offlines raw page / transparent hugepage / HugeTLB hugepage if userspace has agreed to. The interface to userspace is a new sysctl called enable_soft_offline under /proc/sys/vm. By default enable_soft_line is 1 to preserve existing behavior in kernel. Changelog v2 => v3: * incorporate feedbacks from Miaohe Lin , Lance Yang , Oscar Salvador , and David Rientjes . * release potential refcount if enable_soft_offline is 0. * soft_offline_page() returns EOPNOTSUPP if enable_soft_offline is 0. * refactor hugetlb-soft-offline.c, for example, introduce test_soft_offline_common to reduce repeated code. * rewrite enable_soft_offline's documentation, adds more details about the cost of soft-offline for transparent and hugetlb hugepages, and components that are impacted when enable_soft_offline becomes 0. * fix typos in commit messages. * v3 is still based on commit 83a7eefedc9b ("Linux 6.10-rc3"). v1 => v2: * incorporate feedbacks from both Miaohe Lin and Jane Chu . * make the switch to control all pages, instead of HugeTLB specific. * change the API from /sys/kernel/mm/hugepages/hugepages-${size}kB/softoffline_corrected_errors to /proc/sys/vm/enable_soft_offline. * minor update to test code. * update documentation of the user control API. * v2 is based on commit 83a7eefedc9b ("Linux 6.10-rc3"). Jiaqi Yan (3): mm/memory-failure: userspace controls soft-offlining pages selftest/mm: test enable_soft_offline behaviors docs: mm: add enable_soft_offline sysctl Documentation/admin-guide/sysctl/vm.rst | 33 +++ mm/memory-failure.c | 22 +- tools/testing/selftests/mm/.gitignore | 1 + tools/testing/selftests/mm/Makefile | 1 + .../selftests/mm/hugetlb-soft-offline.c | 229 ++++++++++++++++++ tools/testing/selftests/mm/run_vmtests.sh | 4 + 6 files changed, 288 insertions(+), 2 deletions(-) create mode 100644 tools/testing/selftests/mm/hugetlb-soft-offline.c