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From: "Michael S. Tsirkin" <mst@redhat.com>
To: qemu-devel@nongnu.org
Cc: Peter Maydell <peter.maydell@linaro.org>,
	Jason Wang <jasowang@redhat.com>
Subject: [Qemu-devel] [PULL 04/11] virtio-pci: use zero length mmio eventfd for 1.0 notification cap when possible
Date: Thu, 12 Nov 2015 17:09:19 +0200	[thread overview]
Message-ID: <1447340097-18216-5-git-send-email-mst@redhat.com> (raw)
In-Reply-To: <1447340097-18216-1-git-send-email-mst@redhat.com>

From: Jason Wang <jasowang@redhat.com>

We use data match eventfd for 1.0 notification currently. This could
be slow since software decoding is needed for mmio exit. To speed this
up, we can switch to use zero length mmio eventfd for 1.0 notification
since we can examine the queue index directly from the writing
address. KVM kernel module can utilize this by registering it to fast
mmio bus which could be as fast as pio on ept capable machine when
fast mmio is supported by host kernel.

Lots of improvements were seen on a ept capable machine:

Guest RX:(TCP)
size/session/+throughput%/+cpu%/-+per cpu%/
64/1/+1.6807%/[-16.2421%]/[+21.3984%]/
64/2/+0.6091%/[-11.0187%]/[+13.0678%]/
64/4/+0.0553%/[-5.9768%]/[+6.4155%]/
64/8/+0.1206%/[-4.0057%]/[+4.2984%]/
256/1/-0.0031%/[-10.1166%]/[+11.2517%]/
256/2/-0.5058%/[-6.1656%]/+6.0317%]/
...

Guest TX:(TCP)
size/session/+throughput%/+cpu%/-+per cpu%/
64/1/[+18.9183%]/-0.2823%/[+19.2550%]/
64/2/[+13.5714%]/[+2.2675%]/[+11.0533%]/
64/4/[+13.1070%]/[+2.1817%]/[+10.6920%]/
64/8/[+13.0426%]/[+2.0887%]/[+10.7299%]/
256/1/[+36.2761%]/+6.3434%/[+28.1471%]/
...
1024/1/[+44.8873%]/+2.0811%/[+41.9335%]/
...
1024/4/+0.0228%/[-2.2044%]/[+2.2774%]/
...
16384/2/+0.0127%/[-5.0346%]/[+5.3148%]/
...
65535/1/[+0.0062%]/[-4.1183%]/[+4.3017%]/
65535/2/+0.0004%/[-4.2311%]/[+4.4185%]/
65535/4/+0.0107%/[-4.6106%]/[+4.8446%]/
65535/8/-0.0090%/[-5.5178%]/[+5.8306%]/

Latency:(TCP_RR)
size/session/+transaction rate%/+cpu%/-+per cpu%/
64/1/[+6.5248%]/[-9.2882%]/[+17.4322%]/
64/25/[+11.0854%]/[+0.8000%]/[+10.2038%]/
64/50/[+12.1076%]/[+2.4627%]/[+9.4131%]/
256/1/[+5.3677%]/[+10.5669%]/-4.7024%/
256/25/[+5.6402%]/-0.8962%/[+6.5955%]/
256/50/[+5.9685%]/[+1.7766%]/[+4.1188%]/
4096/1/+0.2508%/[-10.4941%]/[+12.0047%]/
4096/25/[+1.8533%]/-0.0273%/+1.8812%/
4096/50/[+1.2156%]/-1.4134%/+2.6667%/

Notes: data with '[]' is the one whose significance is greater than 95%.

Thanks Wenli Quan <wquan@redhat.com> for the benchmarking.

Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 hw/virtio/virtio-pci.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index ab2a372..9c3f6e3 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -270,6 +270,7 @@ static int virtio_pci_set_host_notifier_internal(VirtIOPCIProxy *proxy,
     EventNotifier *notifier = virtio_queue_get_host_notifier(vq);
     bool legacy = !(proxy->flags & VIRTIO_PCI_FLAG_DISABLE_LEGACY);
     bool modern = !(proxy->flags & VIRTIO_PCI_FLAG_DISABLE_MODERN);
+    bool fast_mmio = kvm_ioeventfd_any_length_enabled();
     MemoryRegion *modern_mr = &proxy->notify.mr;
     MemoryRegion *legacy_mr = &proxy->bar;
     hwaddr modern_addr = QEMU_VIRTIO_PCI_QUEUE_MEM_MULT *
@@ -286,8 +287,13 @@ static int virtio_pci_set_host_notifier_internal(VirtIOPCIProxy *proxy,
         }
         virtio_queue_set_host_notifier_fd_handler(vq, true, set_handler);
         if (modern) {
-            memory_region_add_eventfd(modern_mr, modern_addr, 2,
-                                      true, n, notifier);
+            if (fast_mmio) {
+                memory_region_add_eventfd(modern_mr, modern_addr, 0,
+                                          false, n, notifier);
+            } else {
+                memory_region_add_eventfd(modern_mr, modern_addr, 2,
+                                          false, n, notifier);
+            }
         }
         if (legacy) {
             memory_region_add_eventfd(legacy_mr, legacy_addr, 2,
@@ -295,8 +301,13 @@ static int virtio_pci_set_host_notifier_internal(VirtIOPCIProxy *proxy,
         }
     } else {
         if (modern) {
-            memory_region_del_eventfd(modern_mr, modern_addr, 2,
-                                      true, n, notifier);
+            if (fast_mmio) {
+                memory_region_del_eventfd(modern_mr, modern_addr, 0,
+                                          false, n, notifier);
+            } else {
+                memory_region_del_eventfd(modern_mr, modern_addr, 2,
+                                          false, n, notifier);
+            }
         }
         if (legacy) {
             memory_region_del_eventfd(legacy_mr, legacy_addr, 2,
-- 
MST

  parent reply	other threads:[~2015-11-12 15:09 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-11-12 15:09 [Qemu-devel] [PULL 00/11] virtio, vhost: fixes for 2.5 Michael S. Tsirkin
2015-11-12 15:09 ` [Qemu-devel] [PULL 01/11] virtio-pci: fix 1.0 virtqueue migration Michael S. Tsirkin
2015-11-12 15:09 ` [Qemu-devel] [PULL 02/11] memory: don't try to adjust endianness for zero length eventfd Michael S. Tsirkin
2015-11-12 15:09 ` [PULL 03/11] KVM: add support for any length io eventfd Michael S. Tsirkin
2015-11-12 15:09   ` [Qemu-devel] " Michael S. Tsirkin
2015-11-12 15:09 ` Michael S. Tsirkin [this message]
2015-11-12 15:09 ` [Qemu-devel] [PULL 05/11] virtio-pci: introduce pio notification capability for modern device Michael S. Tsirkin
2015-11-12 15:09 ` [Qemu-devel] [PULL 06/11] virtio-pci: unbreak queue_enable read Michael S. Tsirkin
2015-11-12 15:09 ` [Qemu-devel] [PULL 07/11] vhost-user: modify SET_LOG_BASE to pass mmap size and offset Michael S. Tsirkin
2015-11-12 15:09 ` [Qemu-devel] [PULL 08/11] vhost: rename RESET_DEVICE backto RESET_OWNER Michael S. Tsirkin
2015-11-12 15:09 ` [Qemu-devel] [PULL 09/11] vhost: send SET_VRING_ENABLE at start/stop Michael S. Tsirkin
2015-11-12 15:09 ` [Qemu-devel] [PULL 10/11] hw/virtio: Add PCIe capability to virtio devices Michael S. Tsirkin
2015-11-12 15:09 ` [Qemu-devel] [PULL 11/11] virtio-9p: add savem handlers Michael S. Tsirkin
2015-11-12 16:06 ` [Qemu-devel] [PULL 00/11] virtio, vhost: fixes for 2.5 Peter Maydell

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