From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx134.postini.com [74.125.245.134]) by kanga.kvack.org (Postfix) with SMTP id F0A656B0069 for ; Mon, 29 Oct 2012 14:22:16 -0400 (EDT) Received: by mail-da0-f41.google.com with SMTP id i14so2759274dad.14 for ; Mon, 29 Oct 2012 11:22:15 -0700 (PDT) Date: Mon, 29 Oct 2012 11:22:09 -0700 From: Tejun Heo Subject: Re: [PATCH v7 15/16] openvswitch: use new hashtable implementation Message-ID: <20121029182209.GB4066@htj.dyndns.org> References: <1351450948-15618-1-git-send-email-levinsasha928@gmail.com> <1351450948-15618-15-git-send-email-levinsasha928@gmail.com> <20121029132931.GC16391@Krystal> <20121029155957.GB18834@Krystal> <20121029181648.GB20796@Krystal> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20121029181648.GB20796@Krystal> Sender: owner-linux-mm@kvack.org List-ID: To: Mathieu Desnoyers Cc: Sasha Levin , 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 Hello, On Mon, Oct 29, 2012 at 02:16:48PM -0400, Mathieu Desnoyers wrote: > This is just one example in an attempt to show why different hash table > users may have different constraints: for a hash table entirely > populated by keys generated internally by the kernel, a random seed > might not be required, but for cases where values are fed by user-space > and from the NIC, I would argue that flexibility to implement a > randomizable hash function beats implementation simplicity any time. > > And you could keep the basic use-case simple by providing hints to the > hash_32()/hash_64()/hash_ulong() helpers in comments. If all you need is throwing in a salt value to avoid attacks, can't you just do that from caller side? Scrambling the key before feeding it into hash_*() should work, no? Thanks. -- tejun -- 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