From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx200.postini.com [74.125.245.200]) by kanga.kvack.org (Postfix) with SMTP id 471F36B0044 for ; Tue, 28 Aug 2012 05:56:35 -0400 (EDT) Received: by obhx4 with SMTP id x4so12298026obh.14 for ; Tue, 28 Aug 2012 02:56:34 -0700 (PDT) Message-ID: <503C95E4.3010000@gmail.com> Date: Tue, 28 Aug 2012 11:56:52 +0200 From: Sasha Levin MIME-Version: 1.0 Subject: Re: [PATCH v3 01/17] hashtable: introduce a small and naive hashtable 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> In-Reply-To: <20120825042419.GA27240@Krystal> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Mathieu Desnoyers Cc: Tejun Heo , torvalds@linux-foundation.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, paul.gortmaker@windriver.com, davem@davemloft.net, rostedt@goodmis.org, mingo@elte.hu, ebiederm@xmission.com, aarcange@redhat.com, ericvh@gmail.com, netdev@vger.kernel.org, josh@joshtriplett.org, eric.dumazet@gmail.com, axboe@kernel.dk, agk@redhat.com, dm-devel@redhat.com, neilb@suse.de, ccaulfie@redhat.com, teigland@redhat.com, Trond.Myklebust@netapp.com, bfields@fieldses.org, fweisbec@gmail.com, jesse@nicira.com, venkat.x.venkatsubra@oracle.com, ejt@redhat.com, snitzer@redhat.com, edumazet@google.com, linux-nfs@vger.kernel.org, dev@openvswitch.org, rds-devel@oss.oracle.com, lw@cn.fujitsu.com On 08/25/2012 06:24 AM, Mathieu Desnoyers wrote: > * Tejun Heo (tj@kernel.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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org