From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: spurious completions during NCQ on rt kernel Date: Wed, 28 Nov 2007 09:37:42 +0900 Message-ID: <474CB856.6060807@gmail.com> References: <1A9B2DB3B3ED841DFF005BAC23AE96A51195946069AEEFCB86C1DAE1638E@webmail.aster.pl> <474A4C7B.1060804@rtr.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from ro-out-1112.google.com ([72.14.202.180]:14113 "EHLO ro-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756617AbXK1AiA (ORCPT ); Tue, 27 Nov 2007 19:38:00 -0500 Received: by ro-out-1112.google.com with SMTP id p4so2093551roc for ; Tue, 27 Nov 2007 16:37:58 -0800 (PST) In-Reply-To: <474A4C7B.1060804@rtr.ca> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Mark Lord Cc: jozwicki , jgarzik@pobox.com, linux-ide@vger.kernel.org, mingo@elte.hu Hello, Mark Lord wrote: > Mmmm.. that's interesting. I suppose a big difference between -rt and > vanilla > is in latency between interrupt signal and the interrupt handler > actually running. > > I think in -rt it is slightly *longer*, since the handler is run by a > scheduled > thread instead of directly. > > Anyway, for me, the intriguing point of data here, is that there could > be some > tight soft timing issue that sometimes can make NCQ fail. And our > response to date > with this is to blacklist the drives.. which may or may not be correct now. I think it's interrupt timing problem too. I just received my order of problematic drives. I'll try to reproduce it and find out. At any rate, I think we'll probably have to drop spurious NCQ completion check. Thanks. -- tejun