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 21E7FC4725D for ; Fri, 19 Jan 2024 13:59:06 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rQpOC-0004W9-5L; Fri, 19 Jan 2024 08:58:32 -0500 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 1rQpNy-0004Hj-Kh for qemu-devel@nongnu.org; Fri, 19 Jan 2024 08:58:20 -0500 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 1rQpNu-0000X0-KU for qemu-devel@nongnu.org; Fri, 19 Jan 2024 08:58:15 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1705672693; 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=unTrNnldBqgn7S//uNsJf5/NLVVUxpDqZKQG52+BAwY=; b=GxsBuP+IWBP2VaRijJ0rtGngjHqMFdairXwz527fCUTbKzrK9a5cwb25ramEdhz5wnI4o2 BsZv4dDk9cpJ9++QHcKUXzLmsPh0Dc1NwTMfjDfdJHgDopYpAjqPHocD1xRpmM2eBInG7n 3WAHbZqC8A0K2KF5qm+dVVDXZs0hmMI= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-594-XBaEPJ0zMoCVe4QmbL1vWw-1; Fri, 19 Jan 2024 08:58:08 -0500 X-MC-Unique: XBaEPJ0zMoCVe4QmbL1vWw-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 87BE91C54031; Fri, 19 Jan 2024 13:58:08 +0000 (UTC) Received: from localhost (unknown [10.39.195.31]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7DDF9200A2F4; Fri, 19 Jan 2024 13:58:07 +0000 (UTC) Date: Fri, 19 Jan 2024 08:41:22 -0500 From: Stefan Hajnoczi To: Kevin Wolf Cc: qemu-devel@nongnu.org, Michal Privoznik , Hanna Reitz , qemu-block@nongnu.org, "Michael S. Tsirkin" , Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= , Michael Roth , Eduardo Habkost , Eric Blake , Markus Armbruster , Paolo Bonzini Subject: Re: [PATCH v4 4/4] virtio-blk: add iothread-vq-mapping parameter Message-ID: <20240119134122.GA65300@fedora> References: <20231220134755.814917-1-stefanha@redhat.com> <20231220134755.814917-5-stefanha@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="NyqjRYAwRBLq+sbL" Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.4 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: -45 X-Spam_score: -4.6 X-Spam_bar: ---- X-Spam_report: (-4.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-2.519, 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_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham 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 --NyqjRYAwRBLq+sbL Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Dec 21, 2023 at 02:40:19PM +0100, Kevin Wolf wrote: > Am 20.12.2023 um 14:47 hat Stefan Hajnoczi geschrieben: > > Add the iothread-vq-mapping parameter to assign virtqueues to IOThreads. > > Store the vq:AioContext mapping in the new struct > > VirtIOBlockDataPlane->vq_aio_context[] field and refactor the code to > > use the per-vq AioContext instead of the BlockDriverState's AioContext. > >=20 > > Reimplement --device virtio-blk-pci,iothread=3D and non-IOThread mode by > > assigning all virtqueues to the IOThread and main loop's AioContext in > > vq_aio_context[], respectively. > >=20 > > The comment in struct VirtIOBlockDataPlane about EventNotifiers is > > stale. Remove it. > >=20 > > Signed-off-by: Stefan Hajnoczi >=20 > > @@ -177,19 +238,13 @@ int virtio_blk_data_plane_start(VirtIODevice *vde= v) > > =20 > > trace_virtio_blk_data_plane_start(s); > > =20 > > - r =3D blk_set_aio_context(s->conf->conf.blk, s->ctx, &local_err); > > + r =3D blk_set_aio_context(s->conf->conf.blk, s->vq_aio_context[0], > > + &local_err); > > if (r < 0) { > > error_report_err(local_err); > > goto fail_aio_context; > > } >=20 > This doesn't really have to be an error any more, we'll just submit I/O > from any thread we want no matter what the home AioContext of the > BlockBackend is. >=20 > So the only effect the blk_set_aio_context() has is that other users of > the image try to submit their requests from the same iothread as the > first virtqueue in the hope that this performs a bit better (maybe less > lock contention or whatever the idea was?) Yes, I'll change this. > > - /* Kick right away to begin processing requests already in vring */ > > - for (i =3D 0; i < nvqs; i++) { > > - VirtQueue *vq =3D virtio_get_queue(s->vdev, i); > > - > > - event_notifier_set(virtio_queue_get_host_notifier(vq)); > > - } > > - > > /* > > * These fields must be visible to the IOThread when it processes = the > > * virtqueue, otherwise it will think dataplane has not started ye= t. > > @@ -206,8 +261,12 @@ int virtio_blk_data_plane_start(VirtIODevice *vdev) > > if (!blk_in_drain(s->conf->conf.blk)) { > > for (i =3D 0; i < nvqs; i++) { > > VirtQueue *vq =3D virtio_get_queue(s->vdev, i); > > + AioContext *ctx =3D s->vq_aio_context[i]; > > =20 > > - virtio_queue_aio_attach_host_notifier(vq, s->ctx); > > + /* Kick right away to begin processing requests already in= vring */ > > + event_notifier_set(virtio_queue_get_host_notifier(vq)); >=20 > The old code did this also for blk_in_drain() =3D=3D true. Why don't we n= eed > it there any more? Should the 'if' move inside the loop just around > attaching the notifier? The answer is I'm not 100% sure. Your suggestion is safer, I'll do that. Stefan --NyqjRYAwRBLq+sbL Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmWqfAIACgkQnKSrs4Gr c8gUiQf9Gi1nfJUPMTm1r0Vl2JTTfJDY0NUxS16jL65eU+8dze5+cWX/Eo4TozFO HaVhyArGeBI6MDkt1+vNYwdfLNNUT0cjf1vC/Vb0qDOquA1s858PcuvX5D6/zIr2 AUzodDCnzxUXI/yziE4DTYEt8G635kdM97zY1b6Iurq7GstH0njr8W+p7GwVC+ow i2fCYMvrz03ko488O4j10a4+Jsi2/bMtHoKITr9HI9RCFlsqwyv1ZeULpOx+vHnf 0F0Z2v+g5wJ7hmvEnwTyCkPc63kbT0RIElHqI+DQMDhaGV7dPf64x2cf54yB3DS1 u66MiEhRrFU5hzKfOg4G/zgeKchJzg== =0WG/ -----END PGP SIGNATURE----- --NyqjRYAwRBLq+sbL--