From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) (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 BE88F19D880; Fri, 14 Jun 2024 03:28:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.189 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718335732; cv=none; b=UhIPE4AxTH7n5qu8n7eqWgK8IrCH1sPYLIubHRBpDSI0BZ9QOoC4Iw7MgZIXCBraUnrLfu6C//oGhNWsnk4fhLhggGjBV1uo5eeGItUI1w1szj/AvybH+3b/2AEDP/PeR5ktoMlQR8tjIFDlJ0z/yCTN7hKlbHHiKo5NROvU3dY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718335732; c=relaxed/simple; bh=K1iLU70Rtx5Wn8YozXXVNGmOBID7ZHIlbDltA8tw5UM=; h=Subject:To:CC:References:From:Message-ID:Date:MIME-Version: In-Reply-To:Content-Type; b=u7e6jGcxe4RW0IkQ4IqzqdaZ+ZmFHychfPrA+4RfpSA1LDWJ3Lmqsh+J3KJ5BAuUF+kDJWJWPowoj3XFZoAl3txnvdvGvbuUwBfEyC6rB3gF8aNlL53kosamrz4eZS5FPDPCPkPwTgHg323n7WB8FFSxtf/JXLLqMN8jN65gJBE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.189 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.88.194]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4W0l5k04JSzPqgX; Fri, 14 Jun 2024 11:25:14 +0800 (CST) Received: from canpemm500002.china.huawei.com (unknown [7.192.104.244]) by mail.maildlp.com (Postfix) with ESMTPS id EA0321400DC; Fri, 14 Jun 2024 11:28:40 +0800 (CST) Received: from [10.173.127.72] (10.173.127.72) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.39; Fri, 14 Jun 2024 11:28:40 +0800 Subject: Re: [PATCH v2 1/3] mm/memory-failure: userspace controls soft-offlining pages To: Jiaqi Yan CC: , , , , , , , , , , , , References: <20240611215544.2105970-1-jiaqiyan@google.com> <20240611215544.2105970-2-jiaqiyan@google.com> From: Miaohe Lin Message-ID: <1e6ecf75-c489-7711-3289-e4a396ca9484@huawei.com> Date: Fri, 14 Jun 2024 11:28:39 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <20240611215544.2105970-2-jiaqiyan@google.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To canpemm500002.china.huawei.com (7.192.104.244) On 2024/6/12 5:55, Jiaqi Yan wrote: > Correctable memory errors are very common on servers with large > amount of memory, and are corrected by ECC. Soft offline is kernel's > additional recovery handling for memory pages having (excessive) > corrected memory errors. Impacted page is migrated to a healthy page > if inuse; the original page is discarded for any future use. > Thanks for your update. > 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. s/mmap hugepages MAP_FAILED/fails to mmap 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: s/doing/doing so/ ? > 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 commit gives 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. s/enable_soft_line/enable_soft_offline/ > > Signed-off-by: Jiaqi Yan > --- > mm/memory-failure.c | 16 ++++++++++++++++ > 1 file changed, 16 insertions(+) > > diff --git a/mm/memory-failure.c b/mm/memory-failure.c > index d3c830e817e3..23415fe03318 100644 > --- a/mm/memory-failure.c > +++ b/mm/memory-failure.c > @@ -68,6 +68,8 @@ static int sysctl_memory_failure_early_kill __read_mostly; > > static int sysctl_memory_failure_recovery __read_mostly = 1; > > +static int sysctl_enable_soft_offline __read_mostly = 1; > + > atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0); > > static bool hw_memory_failure __read_mostly = false; > @@ -141,6 +143,15 @@ static struct ctl_table memory_failure_table[] = { > .extra1 = SYSCTL_ZERO, > .extra2 = SYSCTL_ONE, > }, > + { > + .procname = "enable_soft_offline", > + .data = &sysctl_enable_soft_offline, > + .maxlen = sizeof(sysctl_enable_soft_offline), > + .mode = 0644, > + .proc_handler = proc_dointvec_minmax, > + .extra1 = SYSCTL_ZERO, > + .extra2 = SYSCTL_ONE, > + } > }; > > /* > @@ -2771,6 +2782,11 @@ int soft_offline_page(unsigned long pfn, int flags) > bool try_again = true; > struct page *page; > > + if (!sysctl_enable_soft_offline) { > + pr_info("soft offline: %#lx: OS-wide disabled\n", pfn); > + return -EINVAL; > + } > + IMHO, callers might reach here with page refcnt increased. So we have to take care of releasing it first? Also will it be better to return -EOPNOTSUPP or some other better errno? Thanks. .