From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S939406AbdEYVzK (ORCPT ); Thu, 25 May 2017 17:55:10 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:48375 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S939150AbdEYVzF (ORCPT ); Thu, 25 May 2017 17:55:05 -0400 Date: Thu, 25 May 2017 23:55:03 +0200 From: Pavel Machek To: Kevin McKinney Cc: Alan Cox , linux-kernel@vger.kernel.org Subject: Re: Change PAGE_SIZE from minimum 4k to 12k Message-ID: <20170525215503.GA25045@amd> References: <20170525170526.GD3085@amd> <20170525210855.3ca03356@alans-desktop> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="jI8keyz6grp/JLjh" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --jI8keyz6grp/JLjh Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi! > >> > Would it be possible to have a custom block device driver read/write > >> > in increments of 12k instead of reading/writing data in 4k increment= s? > >> > In other words, I would like to change the default page size on a > >> > x86_64 platform (4.4.0 kernel) from 4k to 12k as the minimum page > >> > size? I understand I may have negative performance due to > >> > fragmentation. Any help would be appreciated. > >> > > >> > If this is the wrong mailing list, please let me know the right one = to use. > >> > >> I won't say "no" but ammount of work neccessary is likely measured in > >> man-years. Plus, hardware page size _is_ 4KB. > > > > Or a few other much larger sizes. Not that it actually matters. You can > > implement a larger software page size for a platform but it would still > > neeed to be a power of two, and you'd have trouble running some existing > > binaries for x86. > > > > What problem are you *actually* trying to solve ? >=20 > Thanks for responding! I work for a company that created custom > hardware with 4 banks of drives. Each bank is 12 terabytes; and each > bank is controlled by a separate RAID controller. We created a custom > block device driver that is responsible for moving data to each bank. > The RAID controller will then stripe the data across the appropriate > disks for the specified bank. The problem we are having is by moving > in increments of 4k, we are unable to utilize all 48 terabytes; we are > only able to utilize 32 terabytes. If we could move in increments of > 12K that would allow us to use the full 12 terabytes for each bank. 12TB is not that big.. are we talking spinning rust or something special? I mean, what does it have to do with page size? 48TB device, that's 5 SATA drives... that's not even that big. Pavel --=20 (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo= g.html --jI8keyz6grp/JLjh Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAlknUrcACgkQMOfwapXb+vJQWACfaDSsm5RXegUIbRD0TDs2WB5M VBQAn1i5HGLb0x/s75NnAQkFjpThdwYD =Yppc -----END PGP SIGNATURE----- --jI8keyz6grp/JLjh--