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=-17.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,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 B9424C4321A for ; Thu, 4 Mar 2021 00:27:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 90EC364E62 for ; Thu, 4 Mar 2021 00:27:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1350237AbhCDAYC (ORCPT ); Wed, 3 Mar 2021 19:24:02 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:21111 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239520AbhCCK0h (ORCPT ); Wed, 3 Mar 2021 05:26:37 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1614767110; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=hNTEj3ex8wv2ADmkIQmf2LExgG6syL3c0c0xrAzVRSE=; b=MoIyD1DcHkoVsne2OeUC3uJhsGfnXNspvK2a9Fhay0w7ZgaEAc0S3WpUfttSwUij6lL9IN 4LTbBGoiFpWCJDB4r0XcmvZGzw+g4wrBKxo7dQwy3Z5iFcp77rKRZ5r4iwoOQRV9Jshbc0 XThdP++VrYqWhD5zVkWeQNtytTOqrfs= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-316-gIIU8uXZNsWohUsuiuqsZw-1; Wed, 03 Mar 2021 05:09:24 -0500 X-MC-Unique: gIIU8uXZNsWohUsuiuqsZw-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id E6CFD801976; Wed, 3 Mar 2021 10:09:22 +0000 (UTC) Received: from file01.intranet.prod.int.rdu2.redhat.com (file01.intranet.prod.int.rdu2.redhat.com [10.11.5.7]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A946810013DB; Wed, 3 Mar 2021 10:09:19 +0000 (UTC) Received: from file01.intranet.prod.int.rdu2.redhat.com (localhost [127.0.0.1]) by file01.intranet.prod.int.rdu2.redhat.com (8.14.4/8.14.4) with ESMTP id 123A9JHU002022; Wed, 3 Mar 2021 05:09:19 -0500 Received: from localhost (mpatocka@localhost) by file01.intranet.prod.int.rdu2.redhat.com (8.14.4/8.14.4/Submit) with ESMTP id 123A9Jip002018; Wed, 3 Mar 2021 05:09:19 -0500 X-Authentication-Warning: file01.intranet.prod.int.rdu2.redhat.com: mpatocka owned process doing -bs Date: Wed, 3 Mar 2021 05:09:18 -0500 (EST) From: Mikulas Patocka X-X-Sender: mpatocka@file01.intranet.prod.int.rdu2.redhat.com To: JeffleXu cc: Mike Snitzer , Heinz Mauelshagen , axboe@kernel.dk, caspar@linux.alibaba.com, io-uring@vger.kernel.org, linux-block@vger.kernel.org, joseph.qi@linux.alibaba.com, dm-devel@redhat.com, hch@lst.de Subject: Re: [dm-devel] [PATCH 4/4] dm: support I/O polling In-Reply-To: <33fa121a-88a8-5c27-0a43-a7efc9b5b3e3@linux.alibaba.com> Message-ID: References: <20210302190555.201228400@debian-a64.vm> <33fa121a-88a8-5c27-0a43-a7efc9b5b3e3@linux.alibaba.com> User-Agent: Alpine 2.02 (LRH 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On Wed, 3 Mar 2021, JeffleXu wrote: > > > On 3/3/21 3:05 AM, Mikulas Patocka wrote: > > > Support I/O polling if submit_bio_noacct_mq_direct returned non-empty > > cookie. > > > > Signed-off-by: Mikulas Patocka > > > > --- > > drivers/md/dm.c | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > Index: linux-2.6/drivers/md/dm.c > > =================================================================== > > --- linux-2.6.orig/drivers/md/dm.c 2021-03-02 19:26:34.000000000 +0100 > > +++ linux-2.6/drivers/md/dm.c 2021-03-02 19:26:34.000000000 +0100 > > @@ -1682,6 +1682,11 @@ static void __split_and_process_bio(stru > > } > > } > > > > + if (ci.poll_cookie != BLK_QC_T_NONE) { > > + while (atomic_read(&ci.io->io_count) > 1 && > > + blk_poll(ci.poll_queue, ci.poll_cookie, true)) ; > > + } > > + > > /* drop the extra reference count */ > > dec_pending(ci.io, errno_to_blk_status(error)); > > } > > It seems that the general idea of your design is to > 1) submit *one* split bio > 2) blk_poll(), waiting the previously submitted split bio complets No, I submit all the bios and poll for the last one. > and then submit next split bio, repeating the above process. I'm afraid > the performance may be an issue here, since the batch every time > blk_poll() reaps may decrease. Could you benchmark it? > Besides, the submitting routine and polling routine is bound together > here, i.e., polling is always synchronous. __split_and_process_bio calls __split_and_process_non_flush in a loop and __split_and_process_non_flush records the poll cookie in ci.poll_cookie. When we processed all the bios, we poll for the last cookie here: if (ci.poll_cookie != BLK_QC_T_NONE) { while (atomic_read(&ci.io->io_count) > 1 && blk_poll(ci.poll_queue, ci.poll_cookie, true)) ; } Mikulas