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 2D6D3C38147 for ; Tue, 23 Aug 2022 10:12:29 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id AC2E88D0002; Tue, 23 Aug 2022 06:12:28 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A243A8D0001; Tue, 23 Aug 2022 06:12:28 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 89E958D0002; Tue, 23 Aug 2022 06:12:28 -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 76B958D0001 for ; Tue, 23 Aug 2022 06:12:28 -0400 (EDT) Received: from smtpin12.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 44042C14D1 for ; Tue, 23 Aug 2022 10:12:28 +0000 (UTC) X-FDA: 79830442776.12.0BFD31E Received: from out30-56.freemail.mail.aliyun.com (out30-56.freemail.mail.aliyun.com [115.124.30.56]) by imf04.hostedemail.com (Postfix) with ESMTP id 3381E4004D for ; Tue, 23 Aug 2022 10:12:24 +0000 (UTC) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R121e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045168;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=6;SR=0;TI=SMTPD_---0VN1TqVf_1661249538; Received: from 30.97.48.53(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0VN1TqVf_1661249538) by smtp.aliyun-inc.com; Tue, 23 Aug 2022 18:12:19 +0800 Message-ID: <888605a6-9e33-7485-3c90-94375390ea0b@linux.alibaba.com> Date: Tue, 23 Aug 2022 18:12:30 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.12.0 Subject: Re: [PATCH v2 4/5] mm/hugetlb: use PMD page lock to protect CONT-PTE entries To: David Hildenbrand , akpm@linux-foundation.org, songmuchun@bytedance.com, mike.kravetz@oracle.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <88c8a8c68d87429f0fc48e81100f19b71f6e664f.1661240170.git.baolin.wang@linux.alibaba.com> <3661415c-6069-24ed-b647-6fe6993bddae@redhat.com> From: Baolin Wang In-Reply-To: <3661415c-6069-24ed-b647-6fe6993bddae@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit ARC-Authentication-Results: i=1; imf04.hostedemail.com; dkim=none; spf=pass (imf04.hostedemail.com: domain of baolin.wang@linux.alibaba.com designates 115.124.30.56 as permitted sender) smtp.mailfrom=baolin.wang@linux.alibaba.com; dmarc=pass (policy=none) header.from=alibaba.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1661249548; a=rsa-sha256; cv=none; b=s3rYoKWllGygTw+imMHbp1kKyAsYyMde/+exNVeZXfru5gcFjvRwapsLOhVHgjsQ7M4j9f v5zECOLMKfd/RsT8QSJHYwwZGplk8t+dyr4eYfMgRAIZQXwDjcxu4aBZcHSO3x5fjjAFSA qBXYmcCo0MYPRXysMg4nP1kp7Ak61rA= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1661249548; 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=gf4vn8VwRpcOgqPmf4ylDXd37a2kbiJmZ3eaiq4+fYY=; b=HAp4UqjEdSAmGb2xEsqxQ5V2OYo6ttb9BgLngpobMVKRSyFrOW6Pk21PVGKY8aQsMuhxVS laOMNacV6YuMnu0hA+u5JduWMtGO+Of+dzBcXrsi+P0avByuxoIwwyEPcNNpWzgt+5lNXF uGa6lkTbrrbZbrS+b6ZdfsMDxccVpjY= Authentication-Results: imf04.hostedemail.com; dkim=none; spf=pass (imf04.hostedemail.com: domain of baolin.wang@linux.alibaba.com designates 115.124.30.56 as permitted sender) smtp.mailfrom=baolin.wang@linux.alibaba.com; dmarc=pass (policy=none) header.from=alibaba.com X-Rspam-User: X-Rspamd-Queue-Id: 3381E4004D X-Rspamd-Server: rspam05 X-Stat-Signature: yzgcofoiza7mj5fwgoasdbcxon6dydrd X-HE-Tag: 1661249544-512787 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 8/23/2022 4:14 PM, David Hildenbrand wrote: > On 23.08.22 09:50, Baolin Wang wrote: >> Considering the pmd entries of a CONT-PMD hugetlb can not span on >> multiple PMDs, we can change to use the PMD page lock, which can >> be much finer grain that lock in the mm. >> >> Signed-off-by: Baolin Wang >> --- >> include/linux/hugetlb.h | 12 ++++++++++-- >> 1 file changed, 10 insertions(+), 2 deletions(-) >> >> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h >> index 3a96f67..d4803a89 100644 >> --- a/include/linux/hugetlb.h >> +++ b/include/linux/hugetlb.h >> @@ -892,9 +892,17 @@ static inline gfp_t htlb_modify_alloc_mask(struct hstate *h, gfp_t gfp_mask) >> static inline spinlock_t *huge_pte_lockptr(struct hstate *h, >> struct mm_struct *mm, pte_t *pte) >> { >> - VM_BUG_ON(huge_page_size(h) == PAGE_SIZE); >> + unsigned long hp_size = huge_page_size(h); >> >> - if (huge_page_size(h) == PMD_SIZE) { >> + VM_BUG_ON(hp_size == PAGE_SIZE); >> + >> + /* >> + * Considering CONT-PMD size hugetlb, since the CONT-PMD entry >> + * can not span multiple PMDs, then we can use the fine grained >> + * PMD page lock. >> + */ >> + if (hp_size == PMD_SIZE || >> + (hp_size > PMD_SIZE && hp_size < PUD_SIZE)) { >> return pmd_lockptr(mm, (pmd_t *) pte); >> } else if (huge_page_size(h) < PMD_SIZE) { >> unsigned long mask = ~(PTRS_PER_PTE * sizeof(pte_t) - 1); > > Is there a measurable performance gain? IOW, do we really care? IMO, It's just a theoretical analysis now:) Let me think about how to measure the performance gain.