From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757213Ab2JQOUG (ORCPT ); Wed, 17 Oct 2012 10:20:06 -0400 Received: from relay.parallels.com ([195.214.232.42]:40279 "EHLO relay.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751748Ab2JQOUF convert rfc822-to-8bit (ORCPT ); Wed, 17 Oct 2012 10:20:05 -0400 Message-ID: <507EBE8C.2030707@parallels.com> Date: Wed, 17 Oct 2012 18:19:56 +0400 From: Stanislav Kinsbursky User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:16.0) Gecko/20121011 Thunderbird/16.0.1 MIME-Version: 1.0 To: Eric Dumazet CC: "peterz@infradead.org" , "mingo@redhat.com" , "tglx@linutronix.de" , "linux-kernel@vger.kernel.org" , "devel@openvz.org" Subject: Re: [RFC PATCH v2] posix timers: allocate timer id per task References: <20121017131732.8781.75295.stgit@localhost.localdomain> <1350481466.26103.464.camel@edumazet-glaptop> In-Reply-To: <1350481466.26103.464.camel@edumazet-glaptop> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 17.10.2012 17:44, Eric Dumazet пишет: > On Wed, 2012-10-17 at 17:18 +0400, Stanislav Kinsbursky wrote: > >> +static int hash(struct signal_struct *sig, unsigned int nr) >> +{ >> + int hash = hash_ptr(sig, POSIX_TIMERS_HASH_BITS); >> + return hash ^ hash_32(nr, POSIX_TIMERS_HASH_BITS); >> +} >> + > > This is quite expensive on 64 bit arches. I suggest instead : > > return hash_32(hash32_ptr(sig) ^ nr, POSIX_TIMERS_HASH_BITS); > > I'm not familiar with hashing costs, so sure, I'll update. -- Best regards, Stanislav Kinsbursky