From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753913Ab2HRWWU (ORCPT ); Sat, 18 Aug 2012 18:22:20 -0400 Received: from out01.mta.xmission.com ([166.70.13.231]:34672 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751462Ab2HRWWO (ORCPT ); Sat, 18 Aug 2012 18:22:14 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: Sasha Levin Cc: Linus Torvalds , Tejun Heo , "linux-kernel\@vger.kernel.org" References: <1344961490-4068-1-git-send-email-levinsasha928@gmail.com> <1344961490-4068-3-git-send-email-levinsasha928@gmail.com> <87txw5hw0s.fsf@xmission.com> <50300E9A.1060501@gmail.com> Date: Sat, 18 Aug 2012 15:21:59 -0700 In-Reply-To: <50300E9A.1060501@gmail.com> (Sasha Levin's message of "Sat, 18 Aug 2012 23:52:26 +0200") Message-ID: <877gsvzvqw.fsf@xmission.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=;;;mid=;;;hst=in02.mta.xmission.com;;;ip=98.207.153.68;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX18+DQTxc9VfVuyKsXqQlr7n7yEn7cJDLk8= X-SA-Exim-Connect-IP: 98.207.153.68 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 1.5 XMNoVowels Alpha-numberic number with no vowels * 0.0 T_TM2_M_HEADER_IN_MSG BODY: T_TM2_M_HEADER_IN_MSG * -3.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% * [score: 0.0000] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa03 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 T_TooManySym_01 4+ unique symbols in subject X-Spam-DCC: XMission; sa03 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Sasha Levin X-Spam-Relay-Country: Subject: Re: [PATCH 02/16] user_ns: use new hashtable implementation X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Fri, 06 Aug 2010 16:31:04 -0600) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Sasha Levin writes: > On 08/15/2012 01:52 AM, Eric W. Biederman wrote: >> Sasha Levin writes: >>> > Switch user_ns to use the new hashtable implementation. This reduces the amount of >>> > generic unrelated code in user_ns. >> Two concerns here. >> 1) When adding a new entry you recompute the hash where previously that >> was not done. I believe that will slow down adding of new entries. > > Since the hashtable doesn't expose the internal hashing to the user of the > hashtable it would require adding a new interface to deal with in. > > I don't feel that a whole new interface to optimize out something which is very > cheap (one multiplication + shift) in this case, I'd rather avoid having a new > interface. > > Is it ok with you if I leave it as is in the next version of the > patch? No problem. I was largely reviewing for potential gotchas, and things that make me go hmm. I don't think setuid is called enough for the hash table to be much of a hotpath. Although I haven't profiled it. Eric