From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 9A60DA7B for ; Fri, 23 Jun 2017 08:49:44 +0000 (UTC) Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 3B947134 for ; Fri, 23 Jun 2017 08:49:44 +0000 (UTC) Date: Fri, 23 Jun 2017 10:49:40 +0200 From: Petr Mladek To: Andrew Lunn Message-ID: <20170623084940.GH23337@pathway.suse.cz> References: <20170619152055.GM3786@lunn.ch> <01a7d603-c0a2-7aae-8c8d-587063da5e61@suse.com> <20170619162317.4nxx6jsvuzvdtasz@sirena.org.uk> <20170620155825.GC409@tigerII.localdomain> <3908561D78D1C84285E8C5FCA982C28F612DAC67@ORSMSX114.amr.corp.intel.com> <20170620171134.GA444@tigerII.localdomain> <20170620172738.zh4maxtfmlwhyrnt@sirena.org.uk> <20170620192858.142a43ff@gandalf.local.home> <20170621122304.GC1538@pathway.suse.cz> <20170621160951.GA20550@lunn.ch> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170621160951.GA20550@lunn.ch> Cc: Peter Zijlstra , "ksummit-discuss@lists.linuxfoundation.org" Subject: Re: [Ksummit-discuss] [TECH TOPIC] printk redesign List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed 2017-06-21 18:09:51, Andrew Lunn wrote: > > 7. Unreliable time stamps and sorting messages > > > > The current extra buffers (cont, printk_safe, printk_safe_nmi) > > makes this worse. The timestamp is added later. > > All you need is a sequence number. Since you have the CPU number > already, it could be a per CPU atomic. And you probably don't even > need to sort the output, if the sequence number is part of the > output. Yup. > How bad is the reordering? Would a sequence space of 256 be > enough? That is very good question and we need a feedback here. I am not sure what fixes are worth the complexity. Best Regards, Petr