From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vladislav Bolkhovitin Subject: Re: [sqlite] light weight write barriers Date: Wed, 14 Nov 2012 20:16:23 -0500 Message-ID: <50A44267.6090103@vlnb.net> 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> <20121102123359.2479a7dc@pyramind.ukuu.org.uk> <50A1C15E.2080605@vlnb.net> <20121113174000.6457a68b@pyramind.ukuu.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Howard Chu , General Discussion of SQLite Database , Theodore Ts'o , drh@hwaci.com, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org To: Alan Cox Return-path: In-Reply-To: <20121113174000.6457a68b@pyramind.ukuu.org.uk> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Alan Cox, on 11/13/2012 12:40 PM wrote: >>> Barriers are pretty much universal as you need them for power off ! >> >> I'm afraid, no storage (drives, if you like this term more) at the moment supports >> barriers and, as far as I know the storage history, has never supported. > > The ATA cache flush is a write barrier, and given you have no NV cache > visible to the controller it's the same thing. The cache flush is cache flush. You can call it barrier, if you want to continue confusing yourself and others. >> Instead, what storage does support in this area are: > > Yes - the devil is in the detail once you go beyond simple capabilities. None of those details brings anything not solvable. For instance, I already described in this thread a simple way how requested order of commands can be carried through the stack and implemented that algorithm in SCST. Vlad