From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753517Ab2HCRj3 (ORCPT ); Fri, 3 Aug 2012 13:39:29 -0400 Received: from mail-bk0-f46.google.com ([209.85.214.46]:49726 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752062Ab2HCRjQ (ORCPT ); Fri, 3 Aug 2012 13:39:16 -0400 Subject: Re: [RFC v2 1/7] hashtable: introduce a small and naive hashtable From: Eric Dumazet To: Sasha Levin Cc: torvalds@linux-foundation.org, tj@kernel.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 In-Reply-To: <1344003788-1417-2-git-send-email-levinsasha928@gmail.com> References: <1344003788-1417-1-git-send-email-levinsasha928@gmail.com> <1344003788-1417-2-git-send-email-levinsasha928@gmail.com> Content-Type: text/plain; charset="UTF-8" Date: Fri, 03 Aug 2012 19:39:10 +0200 Message-ID: <1344015550.9299.1387.camel@edumazet-glaptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2012-08-03 at 16:23 +0200, Sasha Levin wrote: > This hashtable implementation is using hlist buckets to provide a simple > hashtable to prevent it from getting reimplemented all over the kernel. > > +static void hash_add(struct hash_table *ht, struct hlist_node *node, long key) > +{ > + hlist_add_head(node, > + &ht->buckets[hash_long((unsigned long)key, HASH_BITS(ht))]); > +} > + Why key is a long, casted later to "unsigned long" ? hash_long() is expensive on 64bit arches, and not really needed if key is an u32 from the beginning ( I am referring to your patches 6 & 7 using jhash() ) Maybe you could use a macro, so that we can automatically select hash_32() if key is an u32, and hash_long() for other types.