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 82A19C35274 for ; Mon, 18 Dec 2023 12:43:06 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rFCwS-0004kP-0D; Mon, 18 Dec 2023 07:41:52 -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 1rFCwP-0004js-0q; Mon, 18 Dec 2023 07:41:49 -0500 Received: from proxmox-new.maurer-it.com ([94.136.29.106]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rFCwM-0001FF-LT; Mon, 18 Dec 2023 07:41:48 -0500 Received: from proxmox-new.maurer-it.com (localhost.localdomain [127.0.0.1]) by proxmox-new.maurer-it.com (Proxmox) with ESMTP id 55C8D480B4; Mon, 18 Dec 2023 13:41:43 +0100 (CET) Message-ID: <61c149da-ee22-418b-8575-b128b6836e38@proxmox.com> Date: Mon, 18 Dec 2023 13:41:38 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC 0/3] aio-posix: call ->poll_end() when removing AioHandler To: Stefan Hajnoczi Cc: qemu-devel@nongnu.org, Kevin Wolf , qemu-block@nongnu.org, pbonzini@redhat.com, Hanna Reitz , Fam Zheng References: <20231213211544.1601971-1-stefanha@redhat.com> <20231214195352.GB1645604@fedora> Content-Language: en-US From: Fiona Ebner In-Reply-To: <20231214195352.GB1645604@fedora> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=94.136.29.106; envelope-from=f.ebner@proxmox.com; helo=proxmox-new.maurer-it.com X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, 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 Am 14.12.23 um 20:53 schrieb Stefan Hajnoczi: > > I will still try the other approach that Hanna and Paolo have suggested. > It seems more palatable. I will send a v2. > FYI, what I already tried downstream (for VirtIO SCSI): > 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) > > for (uint32_t i = 0; i < total_queues; i++) { > VirtQueue *vq = 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); > } > } 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. 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.: > 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; > } > > - for (uint32_t i = 0; i < total_queues; i++) { > - VirtQueue *vq = virtio_get_queue(vdev, i); > - virtio_queue_aio_attach_host_notifier(vq, s->ctx); > + if (s->bus.drain_count == 0) { > + for (uint32_t i = 0; i < total_queues; i++) { > + VirtQueue *vq = 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); > + } > } > } > Best Regards, Fiona