From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alan Cox Subject: Re: light weight write barriers Date: Fri, 2 Nov 2012 12:33:59 +0000 Message-ID: <20121102123359.2479a7dc@pyramind.ukuu.org.uk> References: <5086F5A7.9090406@vlnb.net> <20121025051445.GA9860@thunk.org> <508B3EED.2080003@vlnb.net> <20121027044456.GA2764@thunk.org> <5090532D.4050902@vlnb.net> <20121031095404.0ac18a4b@pyramind.ukuu.org.uk> <5092D90F.7020105@vlnb.net> <20121101212418.140e3a82@pyramind.ukuu.org.uk> <50931601.4060102@symas.com> Reply-To: General Discussion of SQLite Database Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: General Discussion of SQLite Database , Theodore Ts'o , drh-X1OJI8nnyKUAvxtiuMwx3w@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Vladislav Bolkhovitin To: Howard Chu Return-path: In-Reply-To: <50931601.4060102-aQkYFu9vm6AAvxtiuMwx3w@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: sqlite-users-bounces-CzDROfG0BjIdnm+yROfE0A@public.gmane.org Errors-To: sqlite-users-bounces-CzDROfG0BjIdnm+yROfE0A@public.gmane.org List-Id: linux-fsdevel.vger.kernel.org > Isn't any type of kernel-side ordering an exercise in futility, since > a) the kernel has no knowledge of the disk's actual geometry > b) most drives will internally re-order requests anyway They will but only as permitted by the commands queued, so you have some control depending upon the interface capabilities. > c) cheap drives won't support barriers Barriers are pretty much universal as you need them for power off ! > Even assuming the drives honored all your requests without lying, how would > you really want this behavior exposed? From the userland perspective, there > are very few apps that care. Probably only transactional databases, really. And file systems internally sometimes. A file system is after all a transactional database of sorts. Alan