From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sasha Levin Subject: Re: [PATCH v3 01/17] hashtable: introduce a small and naive hashtable Date: Fri, 24 Aug 2012 22:53:45 +0200 Message-ID: <5037E9D9.9000605@gmail.com> References: <1345602432-27673-1-git-send-email-levinsasha928@gmail.com> <1345602432-27673-2-git-send-email-levinsasha928@gmail.com> <20120822180138.GA19212@google.com> <50357840.5020201@gmail.com> <20120823200456.GD14962@google.com> <5037DA47.9010306@gmail.com> <20120824195941.GC21325@google.com> <5037E00B.6090606@gmail.com> <20120824203332.GF21325@google.com> 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, mathieu.desnoyers-vg+e7yoeK/dWk0Htik3J/w@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, lw-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org, teigland-H+wXaHxf7aLQT0dZR+AlfA@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: Tejun Heo Return-path: In-Reply-To: <20120824203332.GF21325-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> 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 On 08/24/2012 10:33 PM, Tejun Heo wrote: > Hello, Sasha. > > On Fri, Aug 24, 2012 at 10:11:55PM +0200, Sasha Levin wrote: >>> If this implementation is about the common trivial case, why not just >>> have the usual DECLARE/DEFINE_HASHTABLE() combination? >> >> When we add the dynamic non-resizable support, how would DEFINE_HASHTABLE() look? > > Hmmm? DECLARE/DEFINE are usually for static ones. Yup, but we could be using the same API for dynamic non-resizable and static if we go with the DECLARE/hash_init. We could switch between them (and other implementations) without having to change the code. >>> I don't know. If we stick to the static (or even !resize dymaic) >>> straight-forward hash - and we need something like that - I don't see >>> what the full encapsulation buys us other than a lot of trivial >>> wrappers. >> >> Which macros do you consider as trivial within the current API? >> >> Basically this entire thing could be reduced to DEFINE/DECLARE_HASHTABLE and >> get_bucket(), but it would make the life of anyone who wants a slightly >> different hashtable a hell. > > Wouldn't the following be enough to get most of the benefits? > > * DECLARE/DEFINE > * hash_head() > * hash_for_each_head() > * hash_add*() > * hash_for_each_possible*() * hash_for_each*() ? Why do we need hash_head/hash_for_each_head()? I haven't stumbled on a place yet that needed direct access to the bucket itself. Consider the following list: - DECLARE - hash_init - hash_add - hash_del - hash_hashed - hash_for_each_[rcu, safe] - hash_for_each_possible[rcu, safe] This basically means 11 macros/functions that would let us have full encapsulation and will make it very easy for future implementations to work with this API instead of making up a new one. It's also not significantly (+~2-3) more than the ones you listed. >> I think that right now the only real trivial wrapper is hash_hashed(), and I >> think it's a price worth paying to have a single hashtable API instead of >> fragmenting it when more implementations come along. > > I'm not objecting strongly against full encapsulation but having this > many thin wrappers makes me scratch my head. > > Thanks. >