Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753739AbaLCQSC (ORCPT ); Wed, 3 Dec 2014 11:18:02 -0500 Received: from mx1.redhat.com ([209.132.183.28]:52953 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752572AbaLCQRw (ORCPT ); Wed, 3 Dec 2014 11:17:52 -0500 Date: Wed, 3 Dec 2014 11:17:49 -0500 From: Mike Snitzer To: device-mapper development , zhangxiao , linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org, agk@redhat.com Subject: Re: The DM_BUFIO_HASH_BITS is defined as 20, any plan to make it flexible? Message-ID: <20141203161749.GA13117@redhat.com> References: <547D7BC6.6070708@windriver.com> <20141202140015.GB5985@redhat.com> <20141203141921.GB6993@debian> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141203141921.GB6993@debian> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 03 2014 at 9:19am -0500, Joe Thornber wrote: > On Tue, Dec 02, 2014 at 09:00:17AM -0500, Mike Snitzer wrote: > > On Tue, Dec 02 2014 at 3:43am -0500, > > zhangxiao wrote: > > > > > Hi Experts, > > > > > > See drivers/md/dm-bufio.c as below: > > > 50 /* > > > 51 * Buffer hash > > > 52 */ > > > 53 #define DM_BUFIO_HASH_BITS 20 > > > 54 #define DM_BUFIO_HASH(block) \ > > > 55 ((((block) >> DM_BUFIO_HASH_BITS) ^ (block)) & \ > > > 56 ((1 << DM_BUFIO_HASH_BITS) - 1)) > > > "drivers/md/dm-bufio.c" 1854L, 45375C > > > > > > DM_BUFIO_HASH_BITS was defined as 20 and it maybe not fit for some > > > use case with limited resources. Do we have any plan to make it more > > > flexible? Like module parameter or something else? > > > > No immediate plans. > > That hash table has been replaced with a red/black tree. > > https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-for-3.19&id=4e420c452b11edf9d510c8180ac66f529e5b6206 Ah yes, you'd think I'd have remembered that change. Thanks for keeping me honest Joe! -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/