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Howlett" , Dave Chinner , "Paul E . McKenney" , Joel Fernandes , Oleksiy Avramchenko , kexec@lists.infradead.org Subject: Re: [PATCH v2 4/9] mm: vmalloc: Remove global vmap_area_root rb-tree Message-ID: References: <20230829081142.3619-1-urezki@gmail.com> <20230829081142.3619-5-urezki@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.1 on 10.11.54.8 X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 2EEA0180024 X-Stat-Signature: it3ci8ufki3kdd9qakmjqp18gz1nym47 X-Rspam-User: X-HE-Tag: 1694079497-937827 X-HE-Meta: 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 uRDpnJaP VH0t1SvIa4ZScmTlxhXpRNa7YWBAlUbdolzncLnqqerkY26MB7cOrfBYIV3Rkz6RlSF9fB+CU2qGR+nxSy2etxHt4qHk5XkN5I0yaYhntOXYM3T9DF2ZbCOLWUc38i390EvVzapiodmJ2T1DXwbggJ7pQLtc+Mqt89rlVghFIYRKm9U9tXnxCBKbaU24ozSRQRSJcm8HnXoSaCZMkl22ePzPBZP1fZJLet6VRwxFd8pHpeuah5qMSzqC53hS+bgAtwLpykoIKy3nzmhE= 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 09/07/23 at 10:17am, Baoquan He wrote: > Add Kazu and Lianbo to CC, and kexec mailing list > > On 08/29/23 at 10:11am, Uladzislau Rezki (Sony) wrote: > > Store allocated objects in a separate nodes. A va->va_start > > address is converted into a correct node where it should > > be placed and resided. An addr_to_node() function is used > > to do a proper address conversion to determine a node that > > contains a VA. > > > > Such approach balances VAs across nodes as a result an access > > becomes scalable. Number of nodes in a system depends on number > > of CPUs divided by two. The density factor in this case is 1/2. > > > > Please note: > > > > 1. As of now allocated VAs are bound to a node-0. It means the > > patch does not give any difference comparing with a current > > behavior; > > > > 2. The global vmap_area_lock, vmap_area_root are removed as there > > is no need in it anymore. The vmap_area_list is still kept and > > is _empty_. It is exported for a kexec only; > > I haven't taken a test, while accessing all nodes' busy tree to get > va of the lowest address could severely impact kcore reading efficiency > on system with many vmap nodes. People doing live debugging via > /proc/kcore will get a little surprise. > > Empty vmap_area_list will break makedumpfile utility, Crash utility > could be impactd too. I checked makedumpfile code, it relys on > vmap_area_list to deduce the vmalloc_start value. Except of the empty vmap_area_list, this patch looks good to me. We may need think of another way to export the vmalloc_start value or deduce it in makedumpfile/Crash utility. And then remove the useless vmap_area_list. I am not sure if we should remove vmap_area_list in this patch because the empty value will cause breakage anyway. Otherwise, Reviewed-by: Baoquan He > > > > > 3. The vmallocinfo and vread() have to be reworked to be able to > > handle multiple nodes. >