Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754270Ab1EETOT (ORCPT ); Thu, 5 May 2011 15:14:19 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:42831 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750950Ab1EETOS (ORCPT ); Thu, 5 May 2011 15:14:18 -0400 Date: Thu, 5 May 2011 21:13:53 +0200 From: Ingo Molnar To: Christoph Lameter Cc: Tejun Heo , Thomas Gleixner , Linus Torvalds , Pekka Enberg , Jens Axboe , Andrew Morton , werner , "H. Peter Anvin" , Linux Kernel Mailing List Subject: Re: [block IO crash] Re: 2.6.39-rc5-git2 boot crashs Message-ID: <20110505191353.GB23311@elte.hu> References: <20110505095421.GD30950@htj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.3.1 -2.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1311 Lines: 33 * Christoph Lameter wrote: > On Thu, 5 May 2011, Tejun Heo wrote: > > > Anyways, that's what I've been thinking. I'll get to it in the next > > devel cycle or the one after that. What do you guys think about soft > > irq masking idea? > > Great idea. Would make the whole irq on/off business much cheaper. The tradeoffs are *not at all* clear and the result (on x86) is not 'much cheaper', at all ... In particular the irq-enable path gets complicated by the need to check the flag and call a hardirq handling function in that case - a far cry from the single-byte POPF instruction. It will be somewhat cheaper cycle-wise - but the code gets bloated, so the instruction cache impact has to be measured carefully. (See my other mail for details.) There's also the fact that PUSHF+CLI+POPF sequence has been getting cheaper all the time with newer hardware generations. CLI+STI is even cheaper, 10 cycles both on Intel and AMD CPUs. So it's an optimization that might get narrower and narrower with every CPU generation. Thanks, 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/