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Shutemov" , Jan Kara , stable References: <20210615012014.1100672-1-jannh@google.com> <50d828d1-2ce6-21b4-0e27-fb15daa77561@nvidia.com> <6d21f8cb-4b72-bdec-386c-684ddbcdada1@suse.cz> From: Vlastimil Babka Message-ID: <2847e923-2366-6a3b-3d76-4513a01981a0@suse.cz> Date: Thu, 17 Jun 2021 18:09:16 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=O8wStvwX; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=F18qGxTS; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=O8wStvwX; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=F18qGxTS; dmarc=none; spf=pass (imf03.hostedemail.com: domain of vbabka@suse.cz designates 195.135.220.28 as permitted sender) smtp.mailfrom=vbabka@suse.cz X-Stat-Signature: 18ggmsmasi9aduqtmouitr7fd5k3sk7u X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: D2DF6C00CBFC X-HE-Tag: 1623946146-214909 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 6/16/21 8:40 PM, Yang Shi wrote: > On Wed, Jun 16, 2021 at 10:27 AM Vlastimil Babka wrote: >> >> On 6/16/21 1:10 AM, Yang Shi wrote: >> > On Tue, Jun 15, 2021 at 5:10 AM Jann Horn wrote: >> >> >> > >> > It might be possible after Mel's "mm/page_alloc: Allow high-order >> > pages to be stored on the per-cpu lists" patch >> > (https://patchwork.kernel.org/project/linux-mm/patch/20210611135753.GC30378@techsingularity.net/). >> >> Those would be percpu indeed, but not "lockless, non-atomic", no? They are >> protected by a local_lock. > > The local_lock is *not* a lock on non-PREEMPT_RT kernel IIUC. It > disables preempt and IRQ. But preempt disable is no-op on non-preempt > kernel. IRQ disable can guarantee it is atomic context, but I'm not > sure if it is equivalent to "atomic freelists" in Jann's context. Hm right, I thought all locks had the acquire/release semantics, but this one is just a barrier().