On Wed, Jul 19, 2023 at 11:25 PM Hawkins Jiawei <yin31...@gmail.com> wrote: > > 在 2023/7/19 20:44, Lei Yang 写道: > > Hello Hawkins and Michael > > > > Looks like there are big changes about vp_vdpa, therefore, if needed, > > QE can test this series in QE's environment before the patch is > > Hi Lei, > > This patch series does not modify the code of vp_vdpa. Instead, it only > modifies how QEMU sends SVQ control commands to the vdpa device. > Hi Hawkins
> Considering that the behavior of the vp_vdpa device differs from that > of real vdpa hardware, would it be possible for you to test this patch > series on a real vdpa device? Yes, there is a hardware device to test it , I will update the test results ASAP. BR Lei > > Thanks! > > > > merged, and provide the result. > > > > BR > > Lei > > > > > > On Wed, Jul 19, 2023 at 8:37 PM Hawkins Jiawei <yin31...@gmail.com> wrote: > >> > >> 在 2023/7/19 17:11, Michael S. Tsirkin 写道: > >>> On Wed, Jul 19, 2023 at 03:53:45PM +0800, Hawkins Jiawei wrote: > >>>> This patchset allows QEMU to delay polling and checking the device > >>>> used buffer until either the SVQ is full or control commands shadow > >>>> buffers are full, instead of polling and checking immediately after > >>>> sending each SVQ control command, so that QEMU can send all the SVQ > >>>> control commands in parallel, which have better performance improvement. > >>>> > >>>> I use vp_vdpa device to simulate vdpa device, and create 4094 VLANS in > >>>> guest to build a test environment for sending multiple CVQ state load > >>>> commands. This patch series can improve latency from 10023 us to > >>>> 8697 us for about 4099 CVQ state load commands, about 0.32 us per > >>>> command. > >>> > >>> Looks like a tiny improvement. > >>> At the same time we have O(n^2) behaviour with memory mappings. > >> > >> Hi Michael, > >> > >> Thanks for your review. > >> > >> I wonder why you say "we have O(n^2) behaviour on memory mappings" here? > >> > >> From my understanding, QEMU maps two page-size buffers as control > >> commands shadow buffers at device startup. These buffers then are used > >> to cache SVQ control commands, where QEMU fills them with multiple SVQ > >> control > >> commands bytes, flushes them when SVQ descriptors are full or these > >> control commands shadow buffers reach their capacity. > >> > >> QEMU repeats this process until all CVQ state load commands have been > >> sent in loading. > >> > >> In this loading process, only control commands shadow buffers > >> translation should be relative to memory mappings, which should be > >> O(log n) behaviour to my understanding(Please correct me if I am wrong). > >> > >>> Not saying we must not do this but I think it's worth > >>> checking where the bottleneck is. My guess would be > >>> vp_vdpa is not doing things in parallel. Want to try fixing that > >> > >> As for "vp_vdpa is not doing things in parallel.", do you mean > >> the vp_vdpa device cannot process QEMU's SVQ control commands > >> in parallel? > >> > >> In this situation, I will try to use real vdpa hardware to > >> test the patch series performance. > >> > >>> to see how far it can be pushed? > >> > >> Currently, I am involved in the "Add virtio-net Control Virtqueue state > >> restore support" project in Google Summer of Code now. Because I am > >> uncertain about the time it will take to fix that problem in the vp_vdpa > >> device, I prefer to complete the gsoc project first. > >> > >> Thanks! > >> > >> > >>> > >>> > >>>> Note that this patch should be based on > >>>> patch "Vhost-vdpa Shadow Virtqueue VLAN support" at [1]. > >>>> > >>>> [1]. https://lists.gnu.org/archive/html/qemu-devel/2023-07/msg03719.html > >>>> > >>>> TestStep > >>>> ======== > >>>> 1. regression testing using vp-vdpa device > >>>> - For L0 guest, boot QEMU with two virtio-net-pci net device with > >>>> `ctrl_vq`, `ctrl_rx`, `ctrl_rx_extra` features on, command line like: > >>>> -device virtio-net-pci,disable-legacy=on,disable-modern=off, > >>>> iommu_platform=on,mq=on,ctrl_vq=on,guest_announce=off, > >>>> indirect_desc=off,queue_reset=off,ctrl_rx=on,ctrl_rx_extra=on,... > >>>> > >>>> - For L1 guest, apply the patch series and compile the source code, > >>>> start QEMU with two vdpa device with svq mode on, enable the `ctrl_vq`, > >>>> `ctrl_rx`, `ctrl_rx_extra` features on, command line like: > >>>> -netdev type=vhost-vdpa,x-svq=true,... > >>>> -device virtio-net-pci,mq=on,guest_announce=off,ctrl_vq=on, > >>>> ctrl_rx=on,ctrl_rx_extra=on... > >>>> > >>>> - For L2 source guest, run the following bash command: > >>>> ```bash > >>>> #!/bin/sh > >>>> > >>>> for idx1 in {0..9} > >>>> do > >>>> for idx2 in {0..9} > >>>> do > >>>> for idx3 in {0..6} > >>>> do > >>>> ip link add macvlan$idx1$idx2$idx3 link eth0 > >>>> address 4a:30:10:19:$idx1$idx2:1$idx3 type macvlan mode bridge > >>>> ip link set macvlan$idx1$idx2$idx3 up > >>>> done > >>>> done > >>>> done > >>>> ``` > >>>> - Execute the live migration in L2 source monitor > >>>> > >>>> - Result > >>>> * with this series, QEMU should not trigger any error or warning. > >>>> > >>>> > >>>> > >>>> 2. perf using vp-vdpa device > >>>> - For L0 guest, boot QEMU with two virtio-net-pci net device with > >>>> `ctrl_vq`, `ctrl_vlan` features on, command line like: > >>>> -device virtio-net-pci,disable-legacy=on,disable-modern=off, > >>>> iommu_platform=on,mq=on,ctrl_vq=on,guest_announce=off, > >>>> indirect_desc=off,queue_reset=off,ctrl_vlan=on,... > >>>> > >>>> - For L1 guest, apply the patch series, then apply an addtional > >>>> patch to record the load time in microseconds as following: > >>>> ```diff > >>>> diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c > >>>> index 6b958d6363..501b510fd2 100644 > >>>> --- a/hw/net/vhost_net.c > >>>> +++ b/hw/net/vhost_net.c > >>>> @@ -295,7 +295,10 @@ static int vhost_net_start_one(struct vhost_net > >>>> *net, > >>>> } > >>>> > >>>> if (net->nc->info->load) { > >>>> + int64_t start_us = g_get_monotonic_time(); > >>>> r = net->nc->info->load(net->nc); > >>>> + error_report("vhost_vdpa_net_load() = %ld us", > >>>> + g_get_monotonic_time() - start_us); > >>>> if (r < 0) { > >>>> goto fail; > >>>> } > >>>> ``` > >>>> > >>>> - For L1 guest, compile the code, and start QEMU with two vdpa device > >>>> with svq mode on, enable the `ctrl_vq`, `ctrl_vlan` features on, > >>>> command line like: > >>>> -netdev type=vhost-vdpa,x-svq=true,... > >>>> -device virtio-net-pci,mq=on,guest_announce=off,ctrl_vq=on, > >>>> ctrl_vlan=on... > >>>> > >>>> - For L2 source guest, run the following bash command: > >>>> ```bash > >>>> #!/bin/sh > >>>> > >>>> for idx in {1..4094} > >>>> do > >>>> ip link add link eth0 name vlan$idx type vlan id $idx > >>>> done > >>>> ``` > >>>> > >>>> - wait for some time, then execute the live migration in L2 source > >>>> monitor > >>>> > >>>> - Result > >>>> * with this series, QEMU should not trigger any warning > >>>> or error except something like "vhost_vdpa_net_load() = 8697 us" > >>>> * without this series, QEMU should not trigger any warning > >>>> or error except something like "vhost_vdpa_net_load() = 10023 us" > >>>> > >>>> ChangeLog > >>>> ========= > >>>> v3: > >>>> - refactor vhost_svq_poll() to accept cmds_in_flight > >>>> suggested by Jason and Eugenio > >>>> - refactor vhost_vdpa_net_cvq_add() to make control commands buffers > >>>> is not tied to `s->cvq_cmd_out_buffer` and `s->status`, so we can reuse > >>>> it suggested by Eugenio > >>>> - poll and check when SVQ is full or control commands shadow buffers > >>>> is > >>>> full > >>>> > >>>> v2: https://lore.kernel.org/all/cover.1683371965.git.yin31...@gmail.com/ > >>>> - recover accidentally deleted rows > >>>> - remove extra newline > >>>> - refactor `need_poll_len` to `cmds_in_flight` > >>>> - return -EINVAL when vhost_svq_poll() return 0 or check > >>>> on buffers written by device fails > >>>> - change the type of `in_cursor`, and refactor the > >>>> code for updating cursor > >>>> - return directly when vhost_vdpa_net_load_{mac,mq}() > >>>> returns a failure in vhost_vdpa_net_load() > >>>> > >>>> v1: https://lore.kernel.org/all/cover.1681732982.git.yin31...@gmail.com/ > >>>> > >>>> Hawkins Jiawei (8): > >>>> vhost: Add argument to vhost_svq_poll() > >>>> vdpa: Use iovec for vhost_vdpa_net_cvq_add() > >>>> vhost: Expose vhost_svq_available_slots() > >>>> vdpa: Avoid using vhost_vdpa_net_load_*() outside > >>>> vhost_vdpa_net_load() > >>>> vdpa: Check device ack in vhost_vdpa_net_load_rx_mode() > >>>> vdpa: Move vhost_svq_poll() to the caller of vhost_vdpa_net_cvq_add() > >>>> vdpa: Add cursors to vhost_vdpa_net_loadx() > >>>> vdpa: Send cvq state load commands in parallel > >>>> > >>>> hw/virtio/vhost-shadow-virtqueue.c | 38 ++-- > >>>> hw/virtio/vhost-shadow-virtqueue.h | 3 +- > >>>> net/vhost-vdpa.c | 354 ++++++++++++++++++----------- > >>>> 3 files changed, 249 insertions(+), 146 deletions(-) > >>>> > >>>> -- > >>>> 2.25.1 > >>> > >> > > >
