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: Tue, 28 Aug 2012 11:56:52 +0200 Message-ID: <503C95E4.3010000@gmail.com> References: <50357840.5020201@gmail.com> <20120823200456.GD14962@google.com> <5037DA47.9010306@gmail.com> <20120824195941.GC21325@google.com> <5037E00B.6090606@gmail.com> <20120824203332.GF21325@google.com> <5037E9D9.9000605@gmail.com> <20120824212348.GK21325@google.com> <5038074D.300@gmail.com> <20120824230740.GN21325@google.com> <20120825042419.GA27240@Krystal> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Tejun Heo , 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, 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: Mathieu Desnoyers Return-path: In-Reply-To: <20120825042419.GA27240@Krystal> Sender: linux-nfs-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: netdev.vger.kernel.org On 08/25/2012 06:24 AM, Mathieu Desnoyers wrote: > * Tejun Heo (tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org) wrote: >> Hello, >> >> On Sat, Aug 25, 2012 at 12:59:25AM +0200, Sasha Levin wrote: >>> Thats the thing, the amount of things of things you can do with a given bucket >>> is very limited. You can't add entries to any point besides the head (without >>> walking the entire list). >> >> Kinda my point. We already have all the hlist*() interface to deal >> with such cases. Having something which is evidently the trivial >> hlist hashtable and advertises as such in the interface can be >> helpful. I think we need that more than we need anything fancy. >> >> Heh, this is a debate about which one is less insignificant. I can >> see your point. I'd really like to hear what others think on this. >> >> Guys, do we want something which is evidently trivial hlist hashtable >> which can use hlist_*() API directly or do we want something better >> encapsulated? > > My 2 cents, FWIW: I think this specific effort should target a trivially > understandable API and implementation, for use-cases where one would be > tempted to reimplement his own trivial hash table anyway. So here > exposing hlist internals, with which kernel developers are already > familiar, seems like a good approach in my opinion, because hiding stuff > behind new abstraction might make the target users go away. > > Then, as we see the need, we can eventually merge a more elaborate hash > table with poneys and whatnot, but I would expect that the trivial hash > table implementation would still be useful. There are of course very > compelling reasons to use a more featureful hash table: automatic > resize, RT-aware updates, scalable updates, etc... but I see a purpose > for a trivial implementation. Its primary strong points being: > > - it's trivially understandable, so anyone how want to be really sure > they won't end up debugging the hash table instead of their > work-in-progress code can have a full understanding of it, > - it has few dependencies, which makes it easier to understand and > easier to use in some contexts (e.g. early boot). > > So I'm in favor of not overdoing the abstraction for this trivial hash > table, and honestly I would rather prefer that this trivial hash table > stays trivial. A more elaborate hash table should probably come as a > separate API. > > Thanks, > > Mathieu > Alright, let's keep it simple then. I do want to keep the hash_for_each[rcu,safe] family though. -- 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