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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EF093C433EF for ; Thu, 28 Apr 2022 03:15:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242061AbiD1DSS (ORCPT ); Wed, 27 Apr 2022 23:18:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53492 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239209AbiD1DSQ (ORCPT ); Wed, 27 Apr 2022 23:18:16 -0400 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0B78DDD for ; Wed, 27 Apr 2022 20:15:01 -0700 (PDT) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.57]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4Kpggx0671z1JBfK; Thu, 28 Apr 2022 11:14:05 +0800 (CST) Received: from [10.174.177.76] (10.174.177.76) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Thu, 28 Apr 2022 11:14:59 +0800 Subject: Re: [RFC PATCH v1 1/4] mm, hwpoison, hugetlb: introduce SUBPAGE_INDEX_HWPOISON to save raw error page To: =?UTF-8?B?SE9SSUdVQ0hJIE5BT1lBKOWggOWPoyDnm7TkuZ8p?= CC: Naoya Horiguchi , Andrew Morton , David Hildenbrand , Mike Kravetz , Yang Shi , Oscar Salvador , Muchun Song , "linux-kernel@vger.kernel.org" , Linux-MM References: <20220427042841.678351-1-naoya.horiguchi@linux.dev> <20220427042841.678351-2-naoya.horiguchi@linux.dev> <5b956156-887b-1d91-7831-28a66db53c6a@huawei.com> <20220427130342.GA3915117@hori.linux.bs1.fc.nec.co.jp> From: Miaohe Lin Message-ID: Date: Thu, 28 Apr 2022 11:14:58 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20220427130342.GA3915117@hori.linux.bs1.fc.nec.co.jp> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/4/27 21:03, HORIGUCHI NAOYA(堀口 直也) wrote: > On Wed, Apr 27, 2022 at 03:11:31PM +0800, Miaohe Lin wrote: >> On 2022/4/27 12:28, Naoya Horiguchi wrote: >>> From: Naoya Horiguchi >>> >>> When handling memory error on a hugetlb page, the error handler tries to >>> dissolve and turn it into 4kB pages. If it's successfully dissolved, >>> PageHWPoison flag is moved to the raw error page, so but that's all >> >> s/so but/so/ > > Fixed, thank you. > >> >>> right. However, dissolve sometimes fails, then the error page is left >>> as hwpoisoned hugepage. It's useful if we can retry to dissolve it to >>> save healthy pages, but that's not possible now because the information >>> about where the raw error page is lost. >>> >>> Use the private field of a tail page to keep that information. The code >> >> Only one raw error page is saved now. Should this be ok? I think so as memory >> failure should be rare anyway? > > This is a good point. It might be rare, but maybe we need some consideration > on it. Some ideas in my mind below ... > > - using struct page of all subpages is not compatible with hugetlb_free_vmemmap, > so it's not desirable. Yes, that is not compatible with hugetlb_free_vmemmap. > - defining a linked list starting from hpage[SUBPAGE_INDEX_HWPOISON].private > might be a solution to save the multiple offsets. > - hacking bits in hpage[SUBPAGE_INDEX_HWPOISON].private field to save offset > info in compressed format. For example, for 2MB hugepage there could be > 512 offset numbers, so we can save one offset with 9 bits subfield. > So we can save upto 7 offsets in the field. This is not flexible and > still can't handle many errors. If there are many errors inside one hugetlb page, there might be other serious problems. > - maintaining global data structure to save the pfn of all hwpoison pages > in the system. This might sound overkilling for the current purpose, > but this data structure might be helpful for other purpose, so in the long > run someone might get interested in it. The above ideas sound good. And last one might be more helpful in the memory re-online case: We can restore the hwpoison info using this global data structure. :) Thanks! > >> >>> path of shrinking hugepage pool used this info to try delayed dissolve. >>> >>> Signed-off-by: Naoya Horiguchi >>> --- >>> include/linux/hugetlb.h | 24 ++++++++++++++++++++++++ >>> mm/hugetlb.c | 9 +++++++++ >>> mm/memory-failure.c | 2 ++ >>> 3 files changed, 35 insertions(+) >>> >>> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h >>> index ac2a1d758a80..689e69cb556b 100644 >>> --- a/include/linux/hugetlb.h >>> +++ b/include/linux/hugetlb.h >>> @@ -42,6 +42,9 @@ enum { >>> SUBPAGE_INDEX_CGROUP, /* reuse page->private */ >>> SUBPAGE_INDEX_CGROUP_RSVD, /* reuse page->private */ >>> __MAX_CGROUP_SUBPAGE_INDEX = SUBPAGE_INDEX_CGROUP_RSVD, >>> +#endif >>> +#ifdef CONFIG_CGROUP_HUGETLB >>> + SUBPAGE_INDEX_HWPOISON, >>> #endif >> >> Do we rely on the CONFIG_CGROUP_HUGETLB to store the raw error page? > > No. I meant CONFIG_MEMORY_FAILURE. > # I just copied and pasted the #ifdef line just above, and forget to update > # the CONFIG_* part :( > > Thanks, > Naoya Horiguchi >