From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755853AbaCLRTk (ORCPT ); Wed, 12 Mar 2014 13:19:40 -0400 Received: from mail-pd0-f176.google.com ([209.85.192.176]:42876 "EHLO mail-pd0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754390AbaCLRTj (ORCPT ); Wed, 12 Mar 2014 13:19:39 -0400 Message-ID: <53209729.9030609@kernel.dk> Date: Wed, 12 Mar 2014 11:19:37 -0600 From: Jens Axboe User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.3.0 MIME-Version: 1.0 To: David Vrabel , Felipe Franciosi CC: linux-kernel@vger.kernel.org, Sam Bradshaw Subject: Re: [PATCH 1/2] mtip32xx: Don't bounce IO requests References: <1394640348-9109-1-git-send-email-felipe@paradoxo.org> <1394640348-9109-2-git-send-email-felipe@paradoxo.org> <53208845.5090305@kernel.dk> <532096E8.1010706@citrix.com> In-Reply-To: <532096E8.1010706@citrix.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/12/2014 11:18 AM, David Vrabel wrote: > On 12/03/14 17:08, Felipe Franciosi wrote: >> On Wed, Mar 12, 2014 at 4:16 PM, Jens Axboe wrote: >>> >>> On 03/12/2014 10:05 AM, Felipe Franciosi wrote: >>>> >>>> This device support 64-bit DMA and therefore no IO requests needs bouncing. >>>> On 32-bit systems, blk_queue_bounce() will bounce all IO requests with high >>>> mem pages. This makes performance really really bad. > [...] >>>> --- a/drivers/block/mtip32xx/mtip32xx.c >>>> +++ b/drivers/block/mtip32xx/mtip32xx.c >>>> @@ -4082,8 +4082,6 @@ static void mtip_make_request(struct request_queue *queue, struct bio *bio) >>>> >>>> sg = mtip_hw_get_scatterlist(dd, &tag, unaligned); >>>> if (likely(sg != NULL)) { >>>> - blk_queue_bounce(queue, &bio); >>>> - >>>> if (unlikely((bio)->bi_vcnt > MTIP_MAX_SG)) { >>>> dev_warn(&dd->pdev->dev, >>>> "Maximum number of SGL entries exceeded\n"); >>> >>> >>> That seems to be because the driver forgets to set the DMA >>> capabilities. It needs a blk_queue_bounce_limit() call when it sets up >>> the queue. >> >> Hmm... I see what you are saying. David, would you like to comment? > > Yes, it should also call blk_queue_bounce_limit(..., BLK_BOUNCE_ANY) in > mtip_block_initialize() as well. > > But, only one other driver calls blk_queue_bounce() so it's difficult to > see why this driver would need a call here. That's because most other drivers hook in the appropriate place, and the blk_queue_bounce() is then done by the block layer. -- Jens Axboe