Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262347AbVCPKv2 (ORCPT ); Wed, 16 Mar 2005 05:51:28 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262356AbVCPKv2 (ORCPT ); Wed, 16 Mar 2005 05:51:28 -0500 Received: from mx1.elte.hu ([157.181.1.137]:42419 "EHLO mx1.elte.hu") by vger.kernel.org with ESMTP id S262347AbVCPKvX (ORCPT ); Wed, 16 Mar 2005 05:51:23 -0500 Date: Wed, 16 Mar 2005 11:51:08 +0100 From: Ingo Molnar To: Andrew Morton Cc: rostedt@goodmis.org, rlrevell@joe-job.com, linux-kernel@vger.kernel.org Subject: Re: [patch 0/3] j_state_lock, j_list_lock, remove-bitlocks Message-ID: <20050316105108.GA19570@elte.hu> References: <20050315120053.GA4686@elte.hu> <20050315133540.GB4686@elte.hu> <20050316085029.GA11414@elte.hu> <20050316011510.2a3bdfdb.akpm@osdl.org> <20050316095155.GA15080@elte.hu> <20050316020408.434cc620.akpm@osdl.org> <20050316101906.GA17328@elte.hu> <20050316024022.6d5c4706.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050316024022.6d5c4706.akpm@osdl.org> User-Agent: Mutt/1.4.1i X-ELTE-SpamVersion: MailScanner 4.31.6-itk1 (ELTE 1.2) SpamAssassin 2.63 ClamAV 0.73 X-ELTE-VirusStatus: clean X-ELTE-SpamCheck: no X-ELTE-SpamCheck-Details: score=-4.9, required 5.9, autolearn=not spam, BAYES_00 -4.90 X-ELTE-SpamLevel: X-ELTE-SpamScore: -4 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1484 Lines: 31 * Andrew Morton wrote: > > How much would the +4/+8 bytes size increase in > > buffer_head [on SMP] be frowned upon? > > It wouldn't be the end of the world. I'm not clear on what bits of > the rt-super-low-latency stuff is intended for mainline though? in the long run, most of it. There are no conceptual barriers so far, the -RT tree consists of lots of small details and the PREEMPT_RT framework itself. We are trying to solve (and merge) the small details first (in upstream), so that PREEMPT_RT itself becomes uncontroversial. (and it's not really the low latency that matters mainly - more valuable is the fact that under PREEMPT_RT high latencies are statistically much more unlikely [you need to do some really intentional and easy to see things to introduce high latencies], while in the current upstream kernel, high latencies are often side-effects of pretty normal kernel coding activities, so low latencies are always a catch-up game that can never be truly won for sure. So yes, while a 10 usec worst-case latency under arbitrary Linux workloads [on the right hardware] is indeed sexy, more important is that things are much more deterministic and hence much more trustable from a hard-RT POV.) Ingo - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/