From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f201.google.com (mail-pl1-f201.google.com [209.85.214.201]) (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 70AE01B14E8 for ; Thu, 20 Jun 2024 18:49:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718909342; cv=none; b=JwveUCUlA0qwNp4viETOMqjt9qXjpmbYj5yvaEhj5h/Vz3WiPXWeiaxEzg80wThVNc+qcVME9aAhkQIA/OKprJ3PExTTVuen97ouoiKZ58mfsT922xRbeOxANf/KKyvvMudjnA6bpVXGgW6ZsZKW1283F2zUlpJXibLzHdQlO0M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718909342; c=relaxed/simple; bh=t2XJQlqBCgFWY1Lzks7J4DodAnhbYKX1VO5lOC5ak2M=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=bt+3iSYJxU6oUErENDCS4h+/XkqE0MjDDlJEcr+0lH3CkemvtXzy7coPWKebY6M4p+bPSpKd8CyFTHi4ZWQJ+iDaw3K89Jv/aqcBMCVaPGl/fyb+GNf99iv3sR/ooQwaBQEjEiSUT/gcOIbnjXfZVmeUL7BjhwfJs12bzepClUk= 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=m4xWuTcN; arc=none smtp.client-ip=209.85.214.201 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="m4xWuTcN" Received: by mail-pl1-f201.google.com with SMTP id d9443c01a7336-1f9a3831aa9so11391755ad.0 for ; Thu, 20 Jun 2024 11:49:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1718909340; x=1719514140; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=d9tdNDDl88qMcZ8yPf5Qu/IpIHQAZ5ZqhxULhpb88jo=; b=m4xWuTcNFvfVdO3frICaPfxv1GyJ3EfC2QYyRdnnU+iLZvHulpeaPf57/oO9Ox90Bb JO0W7q8XbIs+SkWWrRDXrBkjVCOLx3joqUXPDEuhGMisIyvqry/um6h5JwjL7T/Yggx4 2UeUuuJ5S4F+2yBXHs2JKCHOyaUljmlMgPjk8RGZyAd2Yb77sUnQ7xvXnlsRX/QDmkJ2 cHfwLieeG3ZKjtDF8s5nfT3YFn87PRHSwEJXes+QQZqcAxGMf9g936TF0kQ1sd6PqLYU Ja4p8bj1Irt+ynFJlTwNV7g5lH2KAflz35BDOHAilriH+mpRumtIbd9xTgibIA7xOnkq V9+Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1718909340; x=1719514140; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=d9tdNDDl88qMcZ8yPf5Qu/IpIHQAZ5ZqhxULhpb88jo=; b=biCwSrOWgo7mM/AGEqEL2pW+EGa9cqNoUAGXTvrj3X1lLX0YnRYAdjO7QehLiILzGU r6hhUITZvCqfssOuLN1cT1NXEeylMJ5bEFOhwwGD/6eOvrispI/6bzo2faYBnXkgtI43 ftfofqF2LQt80lZGVeEbFb6Z25BHum5u1qOFpI+LMni6qLkRbmqmiNRw8JLQOBCSIFjb 5NOq40yG7mJ2AinVk8IPTACQOPAzyOVOENLWNyv8DVvnC+0TL+Gj2M9jxnDp2iUtS16v gxW/39iVv3bLUZU7eAjUoVTvWmJN9Bc8/lkZK0ukewoz9uShgyCtPTIRont2MkF2dYtp eEeA== X-Forwarded-Encrypted: i=1; AJvYcCXjaHae82+6BiGY+7ghbLhJcM2vfn5IMeWb2VFl1npIK1w2ikHBbyBgKQPRZFSJksja3780RU9cqXITBq2nV2JFeh9jHPpnFSHQ X-Gm-Message-State: AOJu0YxBU9/bpofuZBFe9BGk6y+CY88fKo2DZAD0SvmNQV137psPI2bh LsA3weDyPifCrIySXJjty8fT7lFut6Ts9mNYkPgd1H33eKRYWJOCZ7TBc8FyK8NBASg0igdEJFz Ll/rDXRWypg== X-Google-Smtp-Source: AGHT+IGeFtSm0Ob5GbXFXzE2dfom7nuBRbI+HybKNWPf03Ehp6HFBkwzY/nxmSyoKG+btklxI5CDQ60BWXewkA== X-Received: from yjq3.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:272f]) (user=jiaqiyan job=sendgmr) by 2002:a17:903:1cf:b0:1f6:84b5:1e10 with SMTP id d9443c01a7336-1f9aa396c7bmr1298975ad.1.1718909339520; Thu, 20 Jun 2024 11:48:59 -0700 (PDT) Date: Thu, 20 Jun 2024 18:48:52 +0000 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.45.2.741.gdbec12cfda-goog Message-ID: <20240620184856.600717-1-jiaqiyan@google.com> Subject: [PATCH v4 0/4] Userspace controls soft-offline pages From: Jiaqi Yan To: nao.horiguchi@gmail.com, linmiaohe@huawei.com, jane.chu@oracle.com, osalvador@suse.de Cc: muchun.song@linux.dev, akpm@linux-foundation.org, shuah@kernel.org, corbet@lwn.net, 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 Content-Type: text/plain; charset="UTF-8" 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 v3 => v4: * incorporate feedbacks from Miaohe Lin , Andrew Morton , and Oscar Salvador . * insert a refactor commit to unify soft offline's logs to follow "Soft offline: 0x${pfn}: ${message}" format. * some rewords in document: fail => will not perform. * v4 is still based on commit 83a7eefedc9b ("Linux 6.10-rc3"), akpm/mm-stable. v2 => v3: * incorporate feedbacks from Miaohe Lin , Lance Yang , Oscar Salvador , and David Rientjes . * release potential refcount if enable_soft_offline is 0. * soft_offline_page() returns EOPNOTSUPP if enable_soft_offline is 0. * refactor hugetlb-soft-offline.c, for example, introduce test_soft_offline_common to reduce repeated code. * rewrite enable_soft_offline's documentation, adds more details about the cost of soft-offline for transparent and hugetlb hugepages, and components that are impacted when enable_soft_offline becomes 0. * fix typos in commit messages. * v3 is still based on commit 83a7eefedc9b ("Linux 6.10-rc3"). v1 => v2: * incorporate feedbacks from both Miaohe Lin and Jane Chu . * make the switch to control all pages, instead of HugeTLB specific. * change the API from /sys/kernel/mm/hugepages/hugepages-${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 (4): mm/memory-failure: refactor log format in soft offline code 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 | 32 +++ mm/memory-failure.c | 38 ++- 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, 297 insertions(+), 8 deletions(-) create mode 100644 tools/testing/selftests/mm/hugetlb-soft-offline.c -- 2.45.2.741.gdbec12cfda-goog