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Mon, 13 Jun 2022 01:24:04 -0700 (PDT) Date: Mon, 13 Jun 2022 16:24:01 +0800 From: Muchun Song To: Oscar Salvador Cc: mike.kravetz@oracle.com, david@redhat.com, akpm@linux-foundation.org, corbet@lwn.net, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org Subject: Re: [PATCH 2/6] mm: hugetlb_vmemmap: optimize vmemmap_optimize_mode handling Message-ID: References: <20220613063512.17540-1-songmuchun@bytedance.com> <20220613063512.17540-3-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1655108647; a=rsa-sha256; cv=none; b=DUfEPdAHbx6pHwrvuMTOOo3dyy/2fGUbjzzlexowNtcCpyIWmS4fAND9jPKrBbkPmaRwhW 0pVgyQFgDva2LmiyQIcc2e6oj//ce8JpkR3cNbs8I8oOXiThankxWkwIAlj7HkLDDfKKmJ ZoQcabyPHSEzZ/1l+QPi5qCfZKol3oE= ARC-Authentication-Results: i=1; imf30.hostedemail.com; dkim=pass header.d=bytedance-com.20210112.gappssmtp.com header.s=20210112 header.b=0YuVYFrl; 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dmarc=pass (policy=none) header.from=bytedance.com; spf=pass (imf30.hostedemail.com: domain of songmuchun@bytedance.com designates 209.85.214.176 as permitted sender) smtp.mailfrom=songmuchun@bytedance.com X-HE-Tag: 1655108646-924932 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 Mon, Jun 13, 2022 at 10:10:08AM +0200, Oscar Salvador wrote: > On Mon, Jun 13, 2022 at 02:35:08PM +0800, Muchun Song wrote: > > We hold an another reference to hugetlb_optimize_vmemmap_key when > > making vmemmap_optimize_mode on, because we use static_key to tell > > memory_hotplug that memory_hotplug.memmap_on_memory should be > > overridden. However, this rule has gone when we have introduced > > SECTION_CANNOT_OPTIMIZE_VMEMMAP. Therefore, we could simplify > > vmemmap_optimize_mode handling by not holding an another reference > > to hugetlb_optimize_vmemmap_key. > > > > Signed-off-by: Muchun Song > > LGTM, and it looks way nicer, so > > Reviewed-by: Oscar Salvador > Thanks for taking a look. > One question below though > > > -static enum vmemmap_optimize_mode vmemmap_optimize_mode = > > +static bool vmemmap_optimize_enabled = > > IS_ENABLED(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON); > > So, by default vmemmap_optimize_enabled will be on if we have > CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON, but we can always override that > via cmdline, as below, right? > Totally right. CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON only control if the feature is enabled by default when the users do not specify "it should be off" via cmdline. Thanks.