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[2003:cf:d73b:4143:2bf6:228a:1b7a:e384]) by smtp.gmail.com with ESMTPSA id n18-20020a05600c3b9200b0040e4ca7fcb4sm42388131wms.37.2024.01.23.03.25.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 23 Jan 2024 03:25:21 -0800 (PST) Content-Type: multipart/alternative; boundary="------------aJ7CF4e8iHwij30aUT0D9MKL" Message-ID: Date: Tue, 23 Jan 2024 12:25:20 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC 0/3] aio-posix: call ->poll_end() when removing AioHandler Content-Language: en-US To: Fiona Ebner , Paolo Bonzini , Stefan Hajnoczi , qemu-devel@nongnu.org Cc: Kevin Wolf , qemu-block@nongnu.org, Fam Zheng References: <20231213211544.1601971-1-stefanha@redhat.com> <142d6078-1bb9-4116-ac87-7daac16f12d8@redhat.com> <016ac3d1-f6c1-48eb-a714-fb777dff7012@proxmox.com> <94db88e7-1f02-44dd-bc2c-3d9ccf1cce72@redhat.com> <67a36617-9e61-4778-aebf-1e667cb51120@proxmox.com> <3bb5aa0e-ae0a-4fda-a5b5-1bfac86651ac@redhat.com> <8a32f350-e69a-458a-be4e-1d3335e696c6@proxmox.com> From: Hanna Czenczek In-Reply-To: <8a32f350-e69a-458a-be4e-1d3335e696c6@proxmox.com> Received-SPF: pass client-ip=170.10.129.124; envelope-from=hreitz@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -33 X-Spam_score: -3.4 X-Spam_bar: --- X-Spam_report: (-3.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.289, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, HTML_MESSAGE=0.001, 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, 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 This is a multi-part message in MIME format. --------------aJ7CF4e8iHwij30aUT0D9MKL Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 23.01.24 12:12, Fiona Ebner wrote: [...] > I noticed poll_set_started() is not called, because > ctx->fdmon_ops->need_wait(ctx) was true, i.e. ctx->poll_disable_cnt was > positive (I'm using fdmon_poll). I then found this is because of the > notifier for the event vq, being attached with > >> virtio_queue_aio_attach_host_notifier_no_poll(vs->event_vq, s->ctx); > in virtio_scsi_dataplane_start(). But in virtio_scsi_drained_end() it is > attached with virtio_queue_aio_attach_host_notifier() instead of the > _no_poll() variant. So that might be the actual issue here? > > From a quick test, I cannot see the CPU-usage-spike issue with the > following either: > >> diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c >> index 690aceec45..ba1ab8e410 100644 >> --- a/hw/scsi/virtio-scsi.c >> +++ b/hw/scsi/virtio-scsi.c >> @@ -1166,7 +1166,15 @@ 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_aio_attach_host_notifier(vq, s->ctx); >> + if (!virtio_queue_get_notification(vq)) { >> + virtio_queue_set_notification(vq, true); >> + } >> + if (vq == VIRTIO_SCSI_COMMON(s)->event_vq) { >> + virtio_queue_aio_attach_host_notifier_no_poll(vq, s->ctx); >> + } else { >> + virtio_queue_aio_attach_host_notifier(vq, s->ctx); >> + } >> + virtio_queue_notify(vdev, i); >> } >> } Perfect, so we agree on trying it that way. :) Hanna --------------aJ7CF4e8iHwij30aUT0D9MKL Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: 7bit
On 23.01.24 12:12, Fiona Ebner wrote:

[...]

I noticed poll_set_started() is not called, because
ctx->fdmon_ops->need_wait(ctx) was true, i.e. ctx->poll_disable_cnt was
positive (I'm using fdmon_poll). I then found this is because of the
notifier for the event vq, being attached with


virtio_queue_aio_attach_host_notifier_no_poll(vs->event_vq, s->ctx);

in virtio_scsi_dataplane_start(). But in virtio_scsi_drained_end() it is
attached with virtio_queue_aio_attach_host_notifier() instead of the
_no_poll() variant. So that might be the actual issue here?

>From a quick test, I cannot see the CPU-usage-spike issue with the
following either:


diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
index 690aceec45..ba1ab8e410 100644
--- a/hw/scsi/virtio-scsi.c
+++ b/hw/scsi/virtio-scsi.c
@@ -1166,7 +1166,15 @@ 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_aio_attach_host_notifier(vq, s->ctx);
+        if (!virtio_queue_get_notification(vq)) {
+            virtio_queue_set_notification(vq, true);
+        }
+        if (vq == VIRTIO_SCSI_COMMON(s)->event_vq) {
+            virtio_queue_aio_attach_host_notifier_no_poll(vq, s->ctx);
+        } else {
+            virtio_queue_aio_attach_host_notifier(vq, s->ctx);
+        }
+        virtio_queue_notify(vdev, i);
     }
 }

Perfect, so we agree on trying it that way. :)

Hanna
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