From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [RFC] AHCI Command Completion Coalescing(CCC) proposal Date: Fri, 09 Jun 2006 12:43:37 +0900 Message-ID: <4488EE69.7050907@gmail.com> References: <1149751860.29552.79.camel@forrest26.sh.intel.com> <44883BAE.7070406@pobox.com> <1149820043.5721.7.camel@forrest26.sh.intel.com> <4488EB4A.4050501@pobox.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from py-out-1112.google.com ([64.233.166.183]:14727 "EHLO py-out-1112.google.com") by vger.kernel.org with ESMTP id S1751381AbWFIDnn (ORCPT ); Thu, 8 Jun 2006 23:43:43 -0400 Received: by py-out-1112.google.com with SMTP id t32so716013pyc for ; Thu, 08 Jun 2006 20:43:43 -0700 (PDT) In-Reply-To: <4488EB4A.4050501@pobox.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Jeff Garzik Cc: "zhao, forrest" , linux-ide@vger.kernel.org Jeff Garzik wrote: > I'm still not sure I follow you? > > When AHCI runs out of commands to execute, it transitions from H:Idle to > Ccc:SetIS. > > IMPORTANT NOTE: In order for CCC to be effective on AHCI, ahci.c and > libata (and sata_sil24) must be updated to support queuing a list of > non-NCQ commands onto the controller, and recovering from errors in the > case where a command list full of non-NCQ commands is present. I thought about it but am not really sure whether it's worth the trouble. We'll be saving on inter-command latency and interrupt handling which is great but not so sure how noticeable the improvement would be. NCQ is already all around. How about doing CCC only during NCQ command phase? Hmmm... maybe those SSDs would benefit from CCC during non-NCQ commands though if they don't support NCQ, which they don't really need. -- tejun