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 22:11:55 +0200 Message-ID: <5037E00B.6090606@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> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, paul.gortmaker-CWA4WttNNZF54TAoqtyWWQ@public.gmane.org, davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org, rostedt-nx8X9YLhiw1AfugRpC6u6w@public.gmane.org, mingo-X9Un+BFzKDI@public.gmane.org, ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org, aarcange-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, ericvh-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org, eric.dumazet-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, mathieu.desnoyers-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org, axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org, agk-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, dm-devel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, neilb-l3A5Bk7waGM@public.gmane.org, ccaulfie-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, teigland-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, Trond.Myklebust-HgOvQuBEEgTQT0dZR+AlfA@public.gmane.org, bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org, fweisbec-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, jesse-l0M0P4e3n4LQT0dZR+AlfA@public.gmane.org, venkat.x.venkatsubra-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org, ejt-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, snitzer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, edumazet-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, dev-yBygre7rU0TnMu66kgdUjQ@public.gmane.org, rds-devel-N0ozoZBvEnrZJqsBc5GL+g@public.gmane.org, lw-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org To: Tejun Heo Return-path: In-Reply-To: <20120824195941.GC21325-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> Sender: linux-nfs-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: netdev.vger.kernel.org On 08/24/2012 09:59 PM, Tejun Heo wrote: > Hello, Sasha. > > On Fri, Aug 24, 2012 at 09:47:19PM +0200, Sasha Levin wrote: >>> I think this is problematic. It looks exactly like other existing >>> DEFINE macros yet what its semantics is different. I don't think >>> that's a good idea. >> >> I can switch that to be DECLARE_HASHTABLE() if the issue is semantics. > > 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? >>> So, I think it would be best to keep this one as straight-forward and >>> trivial as possible. Helper macros to help its users are fine but >>> let's please not go for full encapsulation. >> >> What if we cut off the dynamic allocated (but not resizable) hashtable out for >> the moment, and focus on the most common statically allocated hashtable case? >> >> The benefits would be: >> >> - Getting rid of all the _size() macros, which will make the amount of helpers >> here reasonable. >> - Dynamically allocated hashtable can be easily added as a separate >> implementation using the same API. We already have some of those in the kernel... > > It seems we have enough of this static usage and solving the static > case first shouldn't hinder the dynamic (!resize) case later, so, > yeah, sounds good to me. > >> - When that's ready, I feel it's a shame to lose full encapsulation just due to >> hash_hashed(). > > 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. 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. Thanks, Sasha > > Thanks. > -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html