From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mathieu Desnoyers Subject: Re: [PATCH v2 01/16] hashtable: introduce a small and naive hashtable Date: Sun, 19 Aug 2012 10:16:41 -0400 Message-ID: <20120819141641.GA9082@Krystal> References: <1345337550-24304-1-git-send-email-levinsasha928@gmail.com> <1345337550-24304-2-git-send-email-levinsasha928@gmail.com> <20120819131637.GA8272@Krystal> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: snitzer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, neilb-l3A5Bk7waGM@public.gmane.org, fweisbec-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, Trond.Myklebust-HgOvQuBEEgTQT0dZR+AlfA@public.gmane.org, bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org, paul.gortmaker-CWA4WttNNZF54TAoqtyWWQ@public.gmane.org, dm-devel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, agk-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, aarcange-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, rds-devel-N0ozoZBvEnrZJqsBc5GL+g@public.gmane.org, eric.dumazet-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, venkat.x.venkatsubra-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org, ccaulfie-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, mingo-X9Un+BFzKDI@public.gmane.org, dev-yBygre7rU0TnMu66kgdUjQ@public.gmane.org, ericvh-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org, rostedt-nx8X9YLhiw1AfugRpC6u6w@public.gmane.org, lw-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org, teigland-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org, linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, edumazet-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, ejt-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org, tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org To: Sasha Levin Return-path: Content-Disposition: inline In-Reply-To: <20120819131637.GA8272@Krystal> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dev-bounces-yBygre7rU0TnMu66kgdUjQ@public.gmane.org Errors-To: dev-bounces-yBygre7rU0TnMu66kgdUjQ@public.gmane.org List-Id: netdev.vger.kernel.org * Mathieu Desnoyers (mathieu.desnoyers-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org) wrote: > * Sasha Levin (levinsasha928-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org) wrote: [...] > > +/** > > + * hash_for_each_possible - iterate over all possible objects for a given key > > + * @name: hashtable to iterate > > + * @obj: the type * to use as a loop cursor for each bucket > > + * @bits: bit count of hashing function of the hashtable > > + * @node: the &struct list_head to use as a loop cursor for each bucket > > + * @member: the name of the hlist_node within the struct > > + * @key: the key of the objects to iterate over > > + */ > > +#define hash_for_each_possible_size(name, obj, bits, node, member, key) \ > > + hlist_for_each_entry(obj, node, &name[hash_min(key, bits)], member) > > Second point: "for_each_possible" does not express the iteration scope. > Citing WordNet: "possible adj 1: capable of happening or existing;" -- > which has nothing to do with iteration on duplicate keys within a hash > table. > > I would recommend to rename "possible" to "duplicate", e.g.: > > hash_for_each_duplicate() > > which clearly says what is the scope of this iteration: duplicate keys. OK, about this part: I now see that you iterate over all objects within the same hash chain. I guess the description "iterate over all possible objects for a given key" is misleading: it's not all objects with a given key, but rather all objects hashing to the same bucket. I understand that you don't want to build knowledge of the key comparison function in the iterator (which makes sense for a simple hash table). By the way, the comment "@obj: the type * to use as a loop cursor for each bucket" is also misleading: it's a loop cursor for each entry, since you iterate on all nodes within single bucket. Same for "@node: the &struct list_head to use as a loop cursor for each bucket". So with these documentation changes applied, hash_for_each_possible starts to make more sense, because it refers to entries that can _possibly_ be a match (or not). Other options would be hash_chain_for_each() or hash_bucket_for_each(). Thanks, Mathieu -- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.com