From mboxrd@z Thu Jan 1 00:00:00 1970 From: zhangxiao Subject: Re: [dm-devel] The DM_BUFIO_HASH_BITS is defined as 20, any plan to make it flexible? Date: Thu, 4 Dec 2014 09:26:19 +0800 Message-ID: <547FB83B.8080401@windriver.com> References: <547D7BC6.6070708@windriver.com> <20141202140015.GB5985@redhat.com> <20141203141921.GB6993@debian> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20141203141921.GB6993@debian> Sender: linux-kernel-owner@vger.kernel.org To: device-mapper development , linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org, agk@redhat.com List-Id: linux-raid.ids On 2014=E5=B9=B412=E6=9C=8803=E6=97=A5 22:19, 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 mor= e >>> 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.g= it/commit/?h=3Ddm-for-3.19&id=3D4e420c452b11edf9d510c8180ac66f529e5b620= 6 > > Great Thanks! Best Regards Xiao