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 83F56C35274 for ; Mon, 18 Dec 2023 14:26:13 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rFEZG-0002E3-M0; Mon, 18 Dec 2023 09:26:02 -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 1rFEZE-00029N-V7 for qemu-devel@nongnu.org; Mon, 18 Dec 2023 09:26:01 -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 1rFEZ3-0008FM-VA for qemu-devel@nongnu.org; Mon, 18 Dec 2023 09:26:00 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1702909546; 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=bhIHOHqaegyYBy0R82VZcKz+55y1HIC2DFKlGayMpsc=; b=fiR7wgFtxm0XPJpZDbnd3ilH9ob99tZwVYl6UBhfPRPBlhR0eq9uG1EtGtfyvVwxgIOxB8 kKVlSBGxiPjSF1gwnzl0cxJwsjZliZLxWmIjrdLM2DDfsgn/yCDlTC2IGspqQAyzTN2qFD fSuc6GO0iy1EEYi7H3JRn5G0chXjh08= 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-588-dfal9ejZN_qk_bsFtD6JWQ-1; Mon, 18 Dec 2023 09:25:12 -0500 X-MC-Unique: dfal9ejZN_qk_bsFtD6JWQ-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (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 81F8E3C29A62; Mon, 18 Dec 2023 14:25:12 +0000 (UTC) Received: from localhost (unknown [10.39.195.94]) by smtp.corp.redhat.com (Postfix) with ESMTP id 0222D1121306; Mon, 18 Dec 2023 14:25:11 +0000 (UTC) Date: Mon, 18 Dec 2023 09:25:10 -0500 From: Stefan Hajnoczi To: Fiona Ebner Cc: qemu-devel@nongnu.org, Kevin Wolf , qemu-block@nongnu.org, pbonzini@redhat.com, Hanna Reitz , Fam Zheng Subject: Re: [RFC 0/3] aio-posix: call ->poll_end() when removing AioHandler Message-ID: <20231218142510.GA12768@fedora> References: <20231213211544.1601971-1-stefanha@redhat.com> <20231214195352.GB1645604@fedora> <61c149da-ee22-418b-8575-b128b6836e38@proxmox.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="wFhZYElCkPY8EqsE" Content-Disposition: inline In-Reply-To: <61c149da-ee22-418b-8575-b128b6836e38@proxmox.com> X-Scanned-By: MIMEDefang 3.4.1 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: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.083, 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=unavailable 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 --wFhZYElCkPY8EqsE Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Dec 18, 2023 at 01:41:38PM +0100, Fiona Ebner wrote: > Am 14.12.23 um 20:53 schrieb Stefan Hajnoczi: > >=20 > > I will still try the other approach that Hanna and Paolo have suggested. > > It seems more palatable. I will send a v2. > >=20 >=20 > FYI, what I already tried downstream (for VirtIO SCSI): >=20 > > diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c > > index 9c751bf296..a6449b04d0 100644 > > --- a/hw/scsi/virtio-scsi.c > > +++ b/hw/scsi/virtio-scsi.c > > @@ -1166,6 +1166,8 @@ static void virtio_scsi_drained_end(SCSIBus *bus) > > =20 > > for (uint32_t i =3D 0; i < total_queues; i++) { > > VirtQueue *vq =3D virtio_get_queue(vdev, i); > > + virtio_queue_set_notification(vq, 1); > > + virtio_queue_notify(vdev, i); > > virtio_queue_aio_attach_host_notifier(vq, s->ctx); > > } > > } >=20 > But this introduces an issue where e.g. a 'backup' QMP command would put > the iothread into a bad state. After the command, whenever the guest > issues IO, the thread will temporarily spike to using 100% CPU. Using > QMP stop+cont is a way to make it go back to normal. >=20 > I think it's because of nested drains, because when additionally > checking that the drain count is zero and only executing the loop then, > that issue doesn't seem to manifest, i.e.: Thanks for letting me know about the issue. I'll keep an eye out for it when playing with the code. Stefan >=20 > > diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c > > index 9c751bf296..d22c586b38 100644 > > --- a/hw/scsi/virtio-scsi.c > > +++ b/hw/scsi/virtio-scsi.c > > @@ -1164,9 +1164,13 @@ static void virtio_scsi_drained_end(SCSIBus *bus) > > return; > > } > > =20 > > - for (uint32_t i =3D 0; i < total_queues; i++) { > > - VirtQueue *vq =3D virtio_get_queue(vdev, i); > > - virtio_queue_aio_attach_host_notifier(vq, s->ctx); > > + if (s->bus.drain_count =3D=3D 0) { > > + for (uint32_t i =3D 0; i < total_queues; i++) { > > + VirtQueue *vq =3D virtio_get_queue(vdev, i); > > + virtio_queue_set_notification(vq, 1); > > + virtio_queue_notify(vdev, i); > > + virtio_queue_aio_attach_host_notifier(vq, s->ctx); > > + } > > } > > } > > =20 >=20 > Best Regards, > Fiona >=20 --wFhZYElCkPY8EqsE Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmWAVkUACgkQnKSrs4Gr c8hsvgf9GflFAzjbK2S6I5WSA9SkH4XEo8igmqR9jwVaFu3wbNqnMXlnJXsb6jx1 PbiTDV5JB9v6wjx9Wr/s54NUii2EiZrfvbFcY55ghCPmpYM+QaChLmiNKGgJ0UsB 0iXkzDotQEFfLJ3KrrTxORRDFmbd3c2lxa1/oJyluAYneKSphf1EQAi+wUnm96Cd 1LbeJpBQb/+z7fi8YNjjUiYuV+prFIs+HbUr8xQLqRMZ2U9LRu7aHA5O0ei3hvvA G+aqNhM2VyvsHmx4lErajvD8jF+DPeUfEi4YU/Me+ul3hdISrcFeQ3DNqFvtuB0f 04cMNPuDp9tala+gNgFk/jskQmw+qg== =Duz4 -----END PGP SIGNATURE----- --wFhZYElCkPY8EqsE--