From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCHv2 05/14] libata: NCQ Encapsulation for READ LOG DMA EXT Date: Thu, 14 Apr 2016 11:43:38 -0400 Message-ID: <20160414154338.GB12583@htj.duckdns.org> References: <1460443678-57934-1-git-send-email-hare@suse.de> <1460443678-57934-6-git-send-email-hare@suse.de> <20160413180735.GD3676@htj.duckdns.org> <570F2E33.3080709@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail-qg0-f67.google.com ([209.85.192.67]:36559 "EHLO mail-qg0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932272AbcDNPnk (ORCPT ); Thu, 14 Apr 2016 11:43:40 -0400 Content-Disposition: inline In-Reply-To: <570F2E33.3080709@suse.de> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Hannes Reinecke Cc: linux-ide@vger.kernel.org, "Martin K. Petersen" , Christoph Hellwig , James Bottomley , Shaun Tancheff , Damien Le Moal , linux-scsi@vger.kernel.org, Hannes Reinecke Hello, Hannes. On Thu, Apr 14, 2016 at 07:44:19AM +0200, Hannes Reinecke wrote: > Hehe. No, it isn't, if you look closely. > (Or make that: it _shouldn't_, and I've messed it up) > (That's what the 'fpdma' parameter is for) > > The benefit is not so much for normal operations, but it'll give us > a performance improvements on SMR drives where we need to issue > READ LOG DMA EXT rather frequently. There we really want to have > them as NCQ commands. I'm still a bit confused. Isn't it part of EH? If so, the path is never traveled with other commands in flight and thus whether a command is NCQ or not doesn't make any difference. The only thing it'd do is making devices which advertise the capability but don't get it quite right fail. Thanks. -- tejun