From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [RFC] add DMA setup FIS auto-activate feature Date: Thu, 23 Jul 2009 12:50:37 +0900 Message-ID: <4A67DE0D.5040101@kernel.org> References: <1248320734.9035.22.camel@sli10-desk.sh.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from hera.kernel.org ([140.211.167.34]:47333 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751331AbZGWDvJ (ORCPT ); Wed, 22 Jul 2009 23:51:09 -0400 In-Reply-To: <1248320734.9035.22.camel@sli10-desk.sh.intel.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Shaohua Li Cc: linux-ide , Jeff Garzik Shaohua Li wrote: > hi, > The SATA spec defines DMA setup FIS auto-activate optimization for FPDMA > transfers. I had an attempt to add it, though my test doesn't show obvious > performance improvement (not worse too), I wonder why not add this feature? > > Signed-off-by: Shaohua Li Eh... It's not clear whether all controllers support AA and it's also not clear whether devices which claim to support AA actually work properly when AA is enabled. For optional features in ATA(PI), the best we can do is probably to allow enabling it from userland or bios. It used to be better for ATA compared to ATAPI but with the introduction of SSDs, the situation has gotten worse rapidly. :-( Thanks. -- tejun