From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 095E7C5DF64 for ; Wed, 6 Nov 2019 11:21:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CCBAF2067B for ; Wed, 6 Nov 2019 11:21:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="mZCFQdnl" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727709AbfKFLVA (ORCPT ); Wed, 6 Nov 2019 06:21:00 -0500 Received: from aserp2120.oracle.com ([141.146.126.78]:59188 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725856AbfKFLVA (ORCPT ); Wed, 6 Nov 2019 06:21:00 -0500 Received: from pps.filterd (aserp2120.oracle.com [127.0.0.1]) by aserp2120.oracle.com (8.16.0.27/8.16.0.27) with SMTP id xA6BIoMI021379; Wed, 6 Nov 2019 11:20:56 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2019-08-05; bh=px4ImXfa1PucqE7mwPB9XH8TbOH5g2GUdu+TeUSn9D0=; b=mZCFQdnlwTq9YVRPSbvpHqE5Go/NuX80v1EGKNa++e3wSHBQn0afscPt9RjAlgcnYnbD fQRzJz7hTCkb/vJ3ZZVDfC+DO4Ta/dNs5rSTbE6/qHTulwcpUJ9aCXU/gFgL368qveV/ XteDYObiwcYVDU2SNxywr6fthLv+qJ1eWe7x+5qlaQt/S+4fX/N1ZWSZeGF/J8FEMmn4 205VwokpfnCg3hDLV6qgC+2Wcjv/yu6Zi0M3F/nFotOBuIlV91L7VMjgk/P/5o8RVFb7 6jP1pCoU3TbxB11cu/Fxbcc1+lEd0+s9OUN3APDa4AslIWoJM7Czv6653t5b6kFTefzs Og== Received: from userp3030.oracle.com (userp3030.oracle.com [156.151.31.80]) by aserp2120.oracle.com with ESMTP id 2w11rq5bxy-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 06 Nov 2019 11:20:56 +0000 Received: from pps.filterd (userp3030.oracle.com [127.0.0.1]) by userp3030.oracle.com (8.16.0.27/8.16.0.27) with SMTP id xA6BKYnn122308; Wed, 6 Nov 2019 11:20:55 GMT Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by userp3030.oracle.com with ESMTP id 2w333x51ek-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 06 Nov 2019 11:20:53 +0000 Received: from abhmp0007.oracle.com (abhmp0007.oracle.com [141.146.116.13]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id xA6BKiZE030195; Wed, 6 Nov 2019 11:20:44 GMT Received: from [192.168.1.14] (/114.88.246.185) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 06 Nov 2019 03:20:44 -0800 Subject: Re: [PATCH v2 2/2] io_uring: io_queue_link*() right after submit To: Pavel Begunkov , Jens Axboe , io-uring@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org References: <85a316b577e1b5204d27a96a7ce452ed6be3c2ae.1572988512.git.asml.silence@gmail.com> <8700c9a3-01aa-2af6-c275-1f17734c2cc5@oracle.com> <81c2db6f-e262-328a-5917-71b30d9390a5@gmail.com> <2600cd84-a953-734c-1972-2c6ae0125ce5@gmail.com> From: Bob Liu Message-ID: <29ff8562-828c-1ae3-9a71-9f3cb3c516eb@oracle.com> Date: Wed, 6 Nov 2019 19:20:40 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: <2600cd84-a953-734c-1972-2c6ae0125ce5@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9432 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1911060117 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9432 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1911060117 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 11/6/19 5:31 PM, Pavel Begunkov wrote: > On 11/6/2019 12:06 PM, Pavel Begunkov wrote: >> On 11/6/2019 11:36 AM, Bob Liu wrote: >>> On 11/6/19 5:22 AM, Pavel Begunkov wrote: >>>> After a call to io_submit_sqe(), it's already known whether it needs >>>> to queue a link or not. Do it there, as it's simplier and doesn't keep >>>> an extra variable across the loop. >>>> >>>> Signed-off-by: Pavel Begunkov >>>> --- >>>> fs/io_uring.c | 22 ++++++++++------------ >>>> 1 file changed, 10 insertions(+), 12 deletions(-) >>>> >>>> diff --git a/fs/io_uring.c b/fs/io_uring.c >>>> index ebe2a4edd644..82c2da99cb5c 100644 >>>> --- a/fs/io_uring.c >>>> +++ b/fs/io_uring.c >>>> @@ -2687,7 +2687,6 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr, >>>> struct io_submit_state state, *statep = NULL; >>>> struct io_kiocb *link = NULL; >>>> struct io_kiocb *shadow_req = NULL; >>>> - bool prev_was_link = false; >>>> int i, submitted = 0; >>>> bool mm_fault = false; >>>> >>>> @@ -2710,17 +2709,6 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr, >>>> } >>>> } >>>> >>>> - /* >>>> - * If previous wasn't linked and we have a linked command, >>>> - * that's the end of the chain. Submit the previous link. >>>> - */ >>>> - if (!prev_was_link && link) { >>>> - io_queue_link_head(ctx, link, &link->submit, shadow_req); >>>> - link = NULL; >>>> - shadow_req = NULL; >>>> - } >>>> - prev_was_link = (s.sqe->flags & IOSQE_IO_LINK) != 0; >>>> - >>>> if (link && (s.sqe->flags & IOSQE_IO_DRAIN)) { >>>> if (!shadow_req) { >>>> shadow_req = io_get_req(ctx, NULL); >>>> @@ -2741,6 +2729,16 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr, >>>> trace_io_uring_submit_sqe(ctx, s.sqe->user_data, true, async); >>>> io_submit_sqe(ctx, &s, statep, &link); >>>> submitted++; >>>> + >>>> + /* >>>> + * If previous wasn't linked and we have a linked command, >>>> + * that's the end of the chain. Submit the previous link. >>>> + */ >>>> + if (!(s.sqe->flags & IOSQE_IO_LINK) && link) >>> The behavior changed to 'current seq' instead of previous after dropping prev_was_link? >>> >> The old behaviour was to remember @prev_was_link for current sqe, and >> use at the beginning of the next iteration, where it becomes >> "previous/last sqe". See, prev_was_link was set after io_queue_link_head. >> >> If @i is iteration idx, then timeline was: >> i: sqe[i-1].is_link -> io_queue_link_head() # if (prev_was_link) >> i: sqe[i].is_link = prev_was_link = (sqe[i].flags & LINK) >> i+1: sqe[i].is_link -> io_queue_link_head() # if (prev_was_link) >> i+1: sqe[i+1].is_link = ... >> >> >> After the change, it's done at the same loop iteration by swapping order >> of checking @prev_was_link and io_queue_link_head(). >> >> i: sqe[i].is_link = ... >> i: sqe[i].is_link -> io_queue_link_head() >> i+1: sqe[i+1].is_link = ... >> i+1: sqe[i+1].is_link -> io_queue_link_head() >> >> Shouldn't change the behavior, if I'm not missing something. >> > And the same goes for ordering with io_submit_sqe(), which assembles a link. > > i: prev_was_link = ... # for sqe[i] > i: io_submit_sqe() # for sqe[i] > i+1: prev_was_link -> io_queue_link_head # for sqe[i] > > after: > i: io_submit_sqe() # for sqe[i] > i: is_link = ... # for sqe[i] > i: is_link -> io_queue_link_head # for sqe[i] > I see, sorry for the noise. Reviewed-by： Bob Liu >> >>>> + io_queue_link_head(ctx, link, &link->submit, shadow_req); >>>> + link = NULL; >>>> + shadow_req = NULL; >>>> + } >>>> } >>>> >>>> if (link) >>>> >>>