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[94.245.46.49]) by smtp.gmail.com with ESMTPSA id m23sm9065936ljb.87.2020.05.04.12.51.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 04 May 2020 12:51:31 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Mon, 4 May 2020 21:51:28 +0200 To: Joel Fernandes , "Paul E. McKenney" Cc: "Paul E. McKenney" , Uladzislau Rezki , LKML , linux-mm , Andrew Morton , "Theodore Y . Ts'o" , Matthew Wilcox , RCU , Oleksiy Avramchenko Subject: Re: [PATCH 09/24] rcu/tree: cache specified number of objects Message-ID: <20200504195128.GA21830@pc636> References: <20200428205903.61704-1-urezki@gmail.com> <20200428205903.61704-10-urezki@gmail.com> <20200501212749.GD7560@paulmck-ThinkPad-P72> <20200504124323.GA17577@pc636> <20200504152437.GK2869@paulmck-ThinkPad-P72> <20200504174822.GA20446@pc636> <20200504180805.GA172409@google.com> <20200504190138.GU2869@paulmck-ThinkPad-P72> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org > > > Since we don't care about traversing backwards, isn't it better to use llist > > > for this usecase? > > > > > > I think Vlad is using locking as we're also tracking the size of the llist to > > > know when to free pages. This tracking could suffer from the lost-update > > > problem without any locking, 2 lockless llist_add happened simulatenously. > > > > > > Also if list_head is used, it will take more space and still use locking. > > > > Indeed, it would be best to use a non-concurrent singly linked list. > > Ok cool :-) > > Is it safe to say something like the following is ruled out? ;-) :-D > #define kfree_rcu_list_add llist_add > In that case i think it is better just to add a comment about using llist_head. To state that it used as a singular list to save space and the access is synchronized by the lock :) IMHO. -- Vlad Rezki