From owner-svn-src-head@FreeBSD.ORG Mon Oct 1 12:58:16 2012 Return-Path: Delivered-To: svn-src-head@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id CCCFC1065672; Mon, 1 Oct 2012 12:58:16 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from bigwig.baldwin.cx (bigknife-pt.tunnel.tserv9.chi1.ipv6.he.net [IPv6:2001:470:1f10:75::2]) by mx1.freebsd.org (Postfix) with ESMTP id A198E8FC18; Mon, 1 Oct 2012 12:58:16 +0000 (UTC) Received: from jhbbsd.localnet (unknown [209.249.190.124]) by bigwig.baldwin.cx (Postfix) with ESMTPSA id 084FAB939; Mon, 1 Oct 2012 08:58:16 -0400 (EDT) From: John Baldwin To: "Andrey V. Elsukov" Date: Mon, 1 Oct 2012 07:53:59 -0400 User-Agent: KMail/1.13.5 (FreeBSD/8.2-CBSD-20110714-p20; KDE/4.5.5; amd64; ; ) References: <201209291647.q8TGlvbr058837@svn.freebsd.org> In-Reply-To: <201209291647.q8TGlvbr058837@svn.freebsd.org> MIME-Version: 1.0 Content-Type: Text/Plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <201210010753.59816.jhb@freebsd.org> X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.2.7 (bigwig.baldwin.cx); Mon, 01 Oct 2012 08:58:16 -0400 (EDT) Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r241053 - in head/sys/boot: common i386/libi386 uboot/lib userboot/userboot X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 01 Oct 2012 12:58:16 -0000 On Saturday, September 29, 2012 12:47:57 pm Andrey V. Elsukov wrote: > Author: ae > Date: Sat Sep 29 16:47:56 2012 > New Revision: 241053 > URL: http://svn.freebsd.org/changeset/base/241053 > > Log: > Almost each time when loader opens a file, this leads to calling > disk_open(). Very often this is called several times for one file. > This leads to reading partition table metadata for each call. To > reduce the number of disk I/O we have a simple block cache, but it > is very dumb and more than half of I/O operations related to reading > metadata, misses this cache. > > Introduce new cache layer to resolve this problem. It is independent > and doesn't need initialization like bcache, and will work by default > for all loaders which use the new DISK API. A successful disk_open() > call to each new disk or partition produces new entry in the cache. > Even more, when disk was already open, now opening of any nested > partitions does not require reading top level partition table. > So, if without this cache, partition table metadata was read around > 20-50 times during boot, now it reads only once. This affects the booting > from GPT and MBR from the UFS. ...and removes support for removable media like floppies. That may be the proper thing to do at this stage (though I think that affects PC98 still perhaps?) However, removing suppot for removable media should be an intentional decision, not a side effect. The bcache was simplistic precisely to support floppies. -- John Baldwin