From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Reinecke Subject: Re: [PATCHv2 05/14] libata: NCQ Encapsulation for READ LOG DMA EXT Date: Thu, 14 Apr 2016 07:44:19 +0200 Message-ID: <570F2E33.3080709@suse.de> References: <1460443678-57934-1-git-send-email-hare@suse.de> <1460443678-57934-6-git-send-email-hare@suse.de> <20160413180735.GD3676@htj.duckdns.org> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from mx2.suse.de ([195.135.220.15]:45880 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752959AbcDNFoZ (ORCPT ); Thu, 14 Apr 2016 01:44:25 -0400 In-Reply-To: <20160413180735.GD3676@htj.duckdns.org> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Tejun Heo 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 On 04/13/2016 08:07 PM, Tejun Heo wrote: > On Tue, Apr 12, 2016 at 08:47:49AM +0200, Hannes Reinecke wrote: >> Recent devices can use NCQ encapsulation for READ LOG DMA EXT, >> so we should be using it if available. >=20 > Does this have any actual benefits than being new and shiny? It's > being called from EH path where we know that no other commands are in > flight. >=20 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. Cheers, Hannes --=20 Dr. Hannes Reinecke Teamlead Storage & Networking hare@suse.de +49 911 74053 688 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 N=FCrnberg GF: F. Imend=F6rffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton HRB 21284 (AG N=FCrnberg)