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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 87E67C433EF for ; Tue, 5 Jul 2022 02:16:46 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 98BA96B0071; Mon, 4 Jul 2022 22:16:45 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 93AD16B0073; Mon, 4 Jul 2022 22:16:45 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 801AC6B0074; Mon, 4 Jul 2022 22:16:45 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 6E73E6B0071 for ; Mon, 4 Jul 2022 22:16:45 -0400 (EDT) Received: from smtpin11.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 3D36320CA6 for ; Tue, 5 Jul 2022 02:16:45 +0000 (UTC) X-FDA: 79651432770.11.6625710 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by imf01.hostedemail.com (Postfix) with ESMTP id 03FB040005 for ; Tue, 5 Jul 2022 02:16:43 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.53]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4LcR8027vfzkWgn; Tue, 5 Jul 2022 10:14:40 +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; Tue, 5 Jul 2022 10:16:39 +0800 Subject: Re: [mm-unstable PATCH v4 1/9] mm/hugetlb: check gigantic_page_runtime_supported() in return_unused_surplus_pages() To: Naoya Horiguchi , CC: Andrew Morton , David Hildenbrand , Mike Kravetz , Liu Shixin , Yang Shi , Oscar Salvador , Muchun Song , Naoya Horiguchi , References: <20220704013312.2415700-1-naoya.horiguchi@linux.dev> <20220704013312.2415700-2-naoya.horiguchi@linux.dev> From: Miaohe Lin Message-ID: <865207df-b272-c7c9-e90c-5748262d3d87@huawei.com> Date: Tue, 5 Jul 2022 10:16:39 +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: <20220704013312.2415700-2-naoya.horiguchi@linux.dev> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit 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 ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1656987404; a=rsa-sha256; cv=none; b=0mr2yjL5Hed56oYBN33DvVGX7SFNq7MYBJDviEyNZZDWB9b9RmHgSgZQj/oHNmePcPZamn F1hb7c7olRvomDNAeeA6Ic4oXYBjt79G6CbLEZ5g5fQaDkYKut3nUPHC6O61BiWBsla3p+ mk494oI0GFdblwFPucVvNaTfMw7oETM= ARC-Authentication-Results: i=1; imf01.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf01.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.188 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1656987404; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=U+rX+f1uZJ/wLZrXoSAtDLKV9nScHRBHdSvxYwIlDwo=; b=XTh2iCbVscZcQtYzPVvQZgws/wAUroRfqqNWu1D2cjYMixOD1AGY7kEnOx4ldBiTbC9DL2 PDyT324ma9SpWIuCMa0kQkUUvtPQFg8dRwSCMc6IADQspuSjCgxvtZdkWFR1C0tYvzG+pY gjYtBWCPAZtSdzKxYenAtK1WFCtVhXM= Authentication-Results: imf01.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf01.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.188 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 03FB040005 X-Rspam-User: X-Stat-Signature: zgofidwdiozpp555xq33cmoq85ewxatq X-HE-Tag: 1656987403-809332 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: On 2022/7/4 9:33, Naoya Horiguchi wrote: > From: Naoya Horiguchi > > I found a weird state of 1GB hugepage pool, caused by the following > procedure: > > - run a process reserving all free 1GB hugepages, > - shrink free 1GB hugepage pool to zero (i.e. writing 0 to > /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages), then > - kill the reserving process. > > , then all the hugepages are free *and* surplus at the same time. > > $ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages > 3 > $ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/free_hugepages > 3 > $ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/resv_hugepages > 0 > $ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/surplus_hugepages > 3 > > This state is resolved by reserving and allocating the pages then > freeing them again, so this seems not to result in serious problem. > But it's a little surprising (shrinking pool suddenly fails). > > This behavior is caused by hstate_is_gigantic() check in > return_unused_surplus_pages(). This was introduced so long ago in 2008 > by commit aa888a74977a ("hugetlb: support larger than MAX_ORDER"), and > at that time the gigantic pages were not supposed to be allocated/freed > at run-time. Now kernel can support runtime allocation/free, so let's > check gigantic_page_runtime_supported() together. > > Signed-off-by: Naoya Horiguchi This patch looks good to me with a few question below. > --- > v2 -> v3: > - Fixed typo in patch description, > - add !gigantic_page_runtime_supported() check instead of removing > hstate_is_gigantic() check (suggested by Miaohe and Muchun) > - add a few more !gigantic_page_runtime_supported() check in > set_max_huge_pages() (by Mike). > --- > mm/hugetlb.c | 19 ++++++++++++++++--- > 1 file changed, 16 insertions(+), 3 deletions(-) > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index 2a554f006255..bdc4499f324b 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -2432,8 +2432,7 @@ static void return_unused_surplus_pages(struct hstate *h, > /* Uncommit the reservation */ > h->resv_huge_pages -= unused_resv_pages; > > - /* Cannot return gigantic pages currently */ > - if (hstate_is_gigantic(h)) > + if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported()) > goto out; > > /* > @@ -3315,7 +3314,8 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid, > * the user tries to allocate gigantic pages but let the user free the > * boottime allocated gigantic pages. > */ > - if (hstate_is_gigantic(h) && !IS_ENABLED(CONFIG_CONTIG_ALLOC)) { > + if (hstate_is_gigantic(h) && (!IS_ENABLED(CONFIG_CONTIG_ALLOC) || > + !gigantic_page_runtime_supported())) { > if (count > persistent_huge_pages(h)) { > spin_unlock_irq(&hugetlb_lock); > mutex_unlock(&h->resize_lock); > @@ -3363,6 +3363,19 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid, > goto out; > } > > + /* > + * We can not decrease gigantic pool size if runtime modification > + * is not supported. > + */ > + if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported()) { > + if (count < persistent_huge_pages(h)) { > + spin_unlock_irq(&hugetlb_lock); > + mutex_unlock(&h->resize_lock); > + NODEMASK_FREE(node_alloc_noretry); > + return -EINVAL; > + } > + } With above change, we're not allowed to decrease the pool size now. But it was allowed previously even if !gigantic_page_runtime_supported. Does this will break user? And it seems it's not allowed to adjust the max_huge_pages now if !gigantic_page_runtime_supported for gigantic huge page. Should we just return for such case as there should be nothing to do now? Or am I miss something? Thanks! > + > /* > * Decrease the pool size > * First return free pages to the buddy allocator (being careful >