Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965008Ab3GRTJa (ORCPT ); Thu, 18 Jul 2013 15:09:30 -0400 Received: from mail.linux-iscsi.org ([67.23.28.174]:36510 "EHLO linux-iscsi.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964817Ab3GRTJ1 (ORCPT ); Thu, 18 Jul 2013 15:09:27 -0400 Message-ID: <1374174891.7397.964.camel@haakon3.risingtidesystems.com> Subject: Re: [PATCH RESEND 0/1] AHCI: Optimize interrupt processing From: "Nicholas A. Bellinger" To: Alexander Gordeev Cc: Tejun Heo , linux-kernel@vger.kernel.org, linux-ide@vger.kernel.org, Jeff Garzik , Jens Axboe , linux-scsi Date: Thu, 18 Jul 2013 12:14:51 -0700 In-Reply-To: <1374173515.7397.948.camel@haakon3.risingtidesystems.com> References: <20130521235003.GE6985@mtj.dyndns.org> <20130522143923.GD19383@dhcp-26-207.brq.redhat.com> <20130522170305.GD9563@kernel.dk> <20130711102630.GA11133@dhcp-26-207.brq.redhat.com> <1373583637.7397.370.camel@haakon3.risingtidesystems.com> <20130712074559.GA8727@dhcp-26-207.brq.redhat.com> <1373692812.7397.625.camel@haakon3.risingtidesystems.com> <20130716183207.GA6402@dhcp-26-207.brq.redhat.com> <1374010683.7397.880.camel@haakon3.risingtidesystems.com> <20130717161909.GB21468@dhcp-26-207.brq.redhat.com> <1374173515.7397.948.camel@haakon3.risingtidesystems.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.4.4-1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2208 Lines: 51 On Thu, 2013-07-18 at 11:51 -0700, Nicholas A. Bellinger wrote: > On Wed, 2013-07-17 at 18:19 +0200, Alexander Gordeev wrote: > > On Tue, Jul 16, 2013 at 02:38:03PM -0700, Nicholas A. Bellinger wrote: > > > [ 7.927818] scsi_execute(): Calling blk_mq_free_request >>> > > > [ 7.927826] scsi 0:0:0:0: Direct-Access ATA ST9500530NS CC03 PQ: 0 ANSI: 5 > > > > > > OK, so INQUIRY response payload is looking as expected here. > > > > Yep. It is not on the top of my head, but I remember something like INQUIRYs > > are emulated and thus do not have payload. > > > > > [ 7.927960] sd 0:0:0:0: [sda] Sector size 0 reported, assuming 512. > > > [ 7.927964] sd 0:0:0:0: [sda] 1 512-byte logical blocks: (512 B/512 B) > > > [ 7.927965] sd 0:0:0:0: [sda] 0-byte physical blocks > > > > > > Strange.. READ_CAPACITY appears to be returning a payload as zeros..? > > > > Yep. Because blk_execute_rq() does not put the proper callback and data do > > not get copied from sg's to bounce buffer. That is why I tried to use > > blk_mq_execute_rq() instead. Once I do that, data start getting read and > > booting stops elsewhere. > > Mmmmmm. > > The call to blk_queue_bounce() exists within blk_mq_make_request(), but > AFAICT this should still be getting invoked regardless of if the struct > request is dispatched into blk-mq via the modified blk_execute_rq() -> > blk_execute_rq_nowait() -> blk_mq_insert_request() codepath, or directly > via blk_mq_execute_rq().. > > Jens..? > Actually sorry, your right. A call to blk_mq_insert_request() for REQ_TYPE_BLOCK_PC will not invoke blk_queue_bounce() located near the top of blk_mq_execute_rq(), which means that only REQ_TYPE_FS is currently using bounce buffers, if required. Need to think a bit more about what to do here for REQ_TYPE_BLOCK_PC bounce buffer special case with blk_execute_rq(), but I'm thinking that blk_mq_execute_rq() should really not be used here.. Jens..? --nab -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/