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 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B6F75EE4993 for ; Mon, 21 Aug 2023 19:21:03 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qYARd-0005JX-T9; Mon, 21 Aug 2023 15:20:16 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qYARL-0005Ib-M6 for qemu-devel@nongnu.org; Mon, 21 Aug 2023 15:19:52 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qYARJ-0001pK-Kz for qemu-devel@nongnu.org; Mon, 21 Aug 2023 15:19:51 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1692645589; 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=R2+oblAeb9LWKlwrOaEhB2YBYPLABepbBzohYmzi6rU=; b=aw3vxU9oueg1oLG9dyQ0eMEoDNrjIDbhxaAMks7HCMC3CFIKlycfXDWgi5nEHIILGOE3Aw FYT00NDSK/3XPddqWFd9Y53UblUtqYxFwSXX4OVbSsALEzmkENowsfGtDmzcD6LrH1z0zl XvOEq1EzzJN7Dm7i67SpsDZ/SD/Wm80= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-170-F2nWquVEMtqcD_P72pQbOw-1; Mon, 21 Aug 2023 15:19:47 -0400 X-MC-Unique: F2nWquVEMtqcD_P72pQbOw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id D6DC68D40A0; Mon, 21 Aug 2023 19:19:46 +0000 (UTC) Received: from localhost (unknown [10.39.192.103]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6E3391121314; Mon, 21 Aug 2023 19:19:46 +0000 (UTC) Date: Mon, 21 Aug 2023 11:17:20 -0400 From: Stefan Hajnoczi To: Kevin Wolf Cc: qemu-devel@nongnu.org, Hanna Reitz , qemu-block@nongnu.org Subject: Re: [PATCH 0/2] block-backend: process I/O in the current AioContext Message-ID: <20230821151720.GA51352@fedora> References: <20230815160521.3357063-1-stefanha@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="BN4fNXU9f9sogSU9" Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 Received-SPF: pass client-ip=170.10.133.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -4 X-Spam_score: -0.5 X-Spam_bar: / X-Spam_report: (-0.5 / 5.0 requ) BAYES_00=-1.9, DATE_IN_PAST_03_06=1.592, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org --BN4fNXU9f9sogSU9 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Aug 18, 2023 at 05:24:22PM +0200, Kevin Wolf wrote: > Am 15.08.2023 um 18:05 hat Stefan Hajnoczi geschrieben: > > Switch blk_aio_*() APIs over to multi-queue by using > > qemu_get_current_aio_context() instead of blk_get_aio_context(). This c= hange > > will allow devices to process I/O in multiple IOThreads in the future. >=20 > Both code paths still use blk_aio_em_aiocb_info, which is: >=20 > static AioContext *blk_aio_em_aiocb_get_aio_context(BlockAIOCB *acb_) > { > BlkAioEmAIOCB *acb =3D container_of(acb_, BlkAioEmAIOCB, common); >=20 > return blk_get_aio_context(acb->rwco.blk); > } >=20 > static const AIOCBInfo blk_aio_em_aiocb_info =3D { > .aiocb_size =3D sizeof(BlkAioEmAIOCB), > .get_aio_context =3D blk_aio_em_aiocb_get_aio_context, > }; >=20 > .get_aio_context() is called by bdrv_aio_cancel(), which already looks > wrong before this patch because in theory it can end up polling the > AioContext of a different thread. After this patch, .get_aio_context() > doesn't even necessarily return the AioContext that runs the request any > more. >=20 > The only thing that might save us is that I can't find any device that > both supports iothreads and calls bdrv_aio_cancel(). But we shouldn't > rely on that. >=20 > Maybe the solution is to just remove .get_aio_context altogether and use > AIO_WAIT_WHILE(NULL, ...) in bdrv_aio_cancel(). I will remove AIOCBInfo.get_aio_context in v2. Stefan --BN4fNXU9f9sogSU9 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmTjgAAACgkQnKSrs4Gr c8jOVQf/V1fZZipr7UrvYByyIQ6IKXrpbrS7A0NTIzxhtZ8EQ8KQP+RWqJKvMigJ Wo3Vy1QAK2EvnY45nLIfOJyj3PxSoOUW25iJTWZsfPXZOEeTwNQ4ownw3nnL1L7T xtihh5AVmI69eZIqVlmUQuMqSBQ0RX2k+J51l/qM39EJg6864A4lKu+GXR0vyNSq dDCGlbGodZMgu2zGo0jydp3mSDydE/kZICX3eOOHIcvnPO9Af5zWYCNNmUWifqU7 g95LmlpiMyk8qtQEt+3bnD+L/1J750CQOx0hdHuEdjsslT9rNdk9eUxqMS/1B64+ Iv0tonEegz8sLdcPY47HLYQ1W1pMSQ== =lfyt -----END PGP SIGNATURE----- --BN4fNXU9f9sogSU9--