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Tue, 03 May 2022 20:37:45 -0700 (PDT) Date: Wed, 4 May 2022 11:37:43 +0800 From: Muchun Song To: Mike Kravetz Cc: corbet@lwn.net, akpm@linux-foundation.org, mcgrof@kernel.org, keescook@chromium.org, yzaikin@google.com, osalvador@suse.de, david@redhat.com, masahiroy@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, duanxiongchun@bytedance.com, smuchun@gmail.com Subject: Re: [PATCH v9 2/4] mm: memory_hotplug: override memmap_on_memory when hugetlb_free_vmemmap=on Message-ID: References: <20220429121816.37541-1-songmuchun@bytedance.com> <20220429121816.37541-3-songmuchun@bytedance.com> <3d040faf-7fc1-80a6-c584-aafeff27af18@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3d040faf-7fc1-80a6-c584-aafeff27af18@oracle.com> X-Rspamd-Queue-Id: CDEFFC0082 X-Stat-Signature: 96w9qbc4wc5isegsgpjrrq9ywanihfb9 Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=bytedance-com.20210112.gappssmtp.com header.s=20210112 header.b=xq0OE+G1; dmarc=pass (policy=none) header.from=bytedance.com; spf=pass (imf10.hostedemail.com: domain of songmuchun@bytedance.com designates 209.85.215.179 as permitted sender) smtp.mailfrom=songmuchun@bytedance.com X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1651635451-135534 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, May 03, 2022 at 05:23:37PM -0700, Mike Kravetz wrote: > On 4/29/22 05:18, Muchun Song wrote: > > When "hugetlb_free_vmemmap=on" and "memory_hotplug.memmap_on_memory" > > are both passed to boot cmdline, the variable of "memmap_on_memory" > > will be set to 1 even if the vmemmap pages will not be allocated from > > the hotadded memory since the former takes precedence over the latter. > > I had to read that sentence a few times before understanding what it was > trying to say. Not insisting, but how about this instead: > Sorry for my poor English. > Freeing HugeTLB vmemmap pages is not compatible with allocating memmap on > hot added memory. If "hugetlb_free_vmemmap=on" and > memory_hotplug.memmap_on_memory" are both passed on the kernel command line, > freeing hugetlb pages takes precedence. However, the global variable > memmap_on_memory will still be set to 1, even though we will not try to > allocate memmap on hot added memory. > > Not sure if that is more clear or not. > Clearer than mine. > Acked-by: Mike Kravetz > Thanks.