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 X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 04754C433E0 for ; Tue, 29 Dec 2020 19:21:45 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 6C4F020825 for ; Tue, 29 Dec 2020 19:21:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6C4F020825 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id A60F46B009B; Tue, 29 Dec 2020 14:21:43 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 9EA3B6B009C; Tue, 29 Dec 2020 14:21:43 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8D91D8D002C; Tue, 29 Dec 2020 14:21:43 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0007.hostedemail.com [216.40.44.7]) by kanga.kvack.org (Postfix) with ESMTP id 70ADC6B009B for ; Tue, 29 Dec 2020 14:21:43 -0500 (EST) Received: from smtpin20.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 35C8A824999B for ; Tue, 29 Dec 2020 19:21:43 +0000 (UTC) X-FDA: 77647289286.20.hill16_31034fc2749e Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin20.hostedemail.com (Postfix) with ESMTP id 1613E180C060D for ; Tue, 29 Dec 2020 19:21:43 +0000 (UTC) X-HE-Tag: hill16_31034fc2749e X-Filterd-Recvd-Size: 2103 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf32.hostedemail.com (Postfix) with ESMTP for ; Tue, 29 Dec 2020 19:21:42 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 80A8420825; Tue, 29 Dec 2020 19:21:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1609269701; bh=8N3BS7r0PFf8OVpv/XwFkacCKHefRmZOfiIuZvpQvPY=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=ansJbd1nGJmfOsBjgv7YcDajDn54lcq60ySAjJghcygVXLnIWarw8t3lON4HODDKC V6/CdV5pt6QWJef7FGXswsQGw6L6QKn0F3SDxqzI0uiaNt4wXy5EJkrykgBnNg/SOO jmpjtUWSIcjLlrEtbi4HwMNT1Doerwb+SriWhet8= Date: Tue, 29 Dec 2020 11:21:40 -0800 From: Andrew Morton To: Li Xinhai Cc: linux-mm@kvack.org, Mike Kravetz , Peter Xu Subject: Re: [PATCH] mm/hugetlb.c: fix unnecessary address expansion of pmd sharing Message-Id: <20201229112140.7f698899cb7f8b04873c79fa@linux-foundation.org> In-Reply-To: <20201229042125.2663029-1-lixinhai.lxh@gmail.com> References: <20201229042125.2663029-1-lixinhai.lxh@gmail.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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 Tue, 29 Dec 2020 12:21:25 +0800 Li Xinhai wrote: > The current code would unnecessarily expand the address range. Consider > one example, (start, end) = (1G-2M, 3G+2M), and (vm_start, vm_end) = > (1G-4M, 3G+4M), the expected adjustment should be keep (1G-2M, 3G+2M) > without expand. But the current result will be (1G-4M, 3G+4M). Actually, > the range (1G-4M, 1G) and (3G, 3G+4M) would never been involved in pmd > sharing. > > After this patch, if pud aligned *start across vm_start, then we know the > *start and vm_start are in same pud_index, and vm_start is not pud > aligned, so don't adjust *start. Same logic applied to *end. Thanks. What are the user-visible runtime effects of this issue?