| Message ID | 20221206081841.2458-3-longpeng2@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | two optimizations to speed up the start time | expand |
On 6/12/22 09:18, Longpeng(Mike) via wrote: > From: Longpeng <longpeng2@huawei.com> > > This allows the vhost-vdpa device to batch the setup of all its MRs of > host notifiers. > > This significantly reduces the device starting time, e.g. the time spend > on setup the host notifier MRs reduce from 423ms to 32ms for a VM with > 64 vCPUs and 3 vhost-vDPA generic devices[1] (64vq per device). > > [1] https://www.mail-archive.com/qemu-devel@nongnu.org/msg921541.html > > Signed-off-by: Longpeng <longpeng2@huawei.com> > --- > hw/virtio/vhost-vdpa.c | 18 ++++++++++++++++++ > 1 file changed, 18 insertions(+) > @@ -562,16 +571,25 @@ static void vhost_vdpa_host_notifiers_init(struct vhost_dev *dev) > return; > } > > + /* > + * Pack all the changes to the memory regions in a single > + * transaction to avoid a few updating of the address space > + * topology. > + */ > + memory_region_transaction_begin(); > + > for (i = dev->vq_index; i < dev->vq_index + dev->nvqs; i++) { > if (vhost_vdpa_host_notifier_init(dev, i)) { > goto err; Could we simplify by replacing this goto statement with: vhost_vdpa_host_notifiers_uninit(dev, i - dev->vq_index); break; ? > } > } > > + memory_region_transaction_commit(); > return; > > err: > vhost_vdpa_host_notifiers_uninit(dev, i - dev->vq_index); > + memory_region_transaction_commit(); > return; > } >
在 2022/12/6 16:30, Philippe Mathieu-Daudé 写道: > On 6/12/22 09:18, Longpeng(Mike) via wrote: >> From: Longpeng <longpeng2@huawei.com> >> >> This allows the vhost-vdpa device to batch the setup of all its MRs of >> host notifiers. >> >> This significantly reduces the device starting time, e.g. the time spend >> on setup the host notifier MRs reduce from 423ms to 32ms for a VM with >> 64 vCPUs and 3 vhost-vDPA generic devices[1] (64vq per device). >> >> [1] https://www.mail-archive.com/qemu-devel@nongnu.org/msg921541.html >> >> Signed-off-by: Longpeng <longpeng2@huawei.com> >> --- >> hw/virtio/vhost-vdpa.c | 18 ++++++++++++++++++ >> 1 file changed, 18 insertions(+) > > >> @@ -562,16 +571,25 @@ static void >> vhost_vdpa_host_notifiers_init(struct vhost_dev *dev) >> return; >> } >> + /* >> + * Pack all the changes to the memory regions in a single >> + * transaction to avoid a few updating of the address space >> + * topology. >> + */ >> + memory_region_transaction_begin(); >> + >> for (i = dev->vq_index; i < dev->vq_index + dev->nvqs; i++) { >> if (vhost_vdpa_host_notifier_init(dev, i)) { >> goto err; > > Could we simplify by replacing this goto statement with: > > vhost_vdpa_host_notifiers_uninit(dev, i - dev->vq_index); > break; > > ? > Good suggestion! I'll do in v3, thanks. >> } >> } >> + memory_region_transaction_commit(); >> return; >> err: >> vhost_vdpa_host_notifiers_uninit(dev, i - dev->vq_index); >> + memory_region_transaction_commit(); >> return; >> } > > .
diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c index 7468e44b87..eb233cf08a 100644 --- a/hw/virtio/vhost-vdpa.c +++ b/hw/virtio/vhost-vdpa.c @@ -547,9 +547,18 @@ static void vhost_vdpa_host_notifiers_uninit(struct vhost_dev *dev, int n) { int i; + /* + * Pack all the changes to the memory regions in a single + * transaction to avoid a few updating of the address space + * topology. + */ + memory_region_transaction_begin(); + for (i = dev->vq_index; i < dev->vq_index + n; i++) { vhost_vdpa_host_notifier_uninit(dev, i); } + + memory_region_transaction_commit(); } static void vhost_vdpa_host_notifiers_init(struct vhost_dev *dev) @@ -562,16 +571,25 @@ static void vhost_vdpa_host_notifiers_init(struct vhost_dev *dev) return; } + /* + * Pack all the changes to the memory regions in a single + * transaction to avoid a few updating of the address space + * topology. + */ + memory_region_transaction_begin(); + for (i = dev->vq_index; i < dev->vq_index + dev->nvqs; i++) { if (vhost_vdpa_host_notifier_init(dev, i)) { goto err; } } + memory_region_transaction_commit(); return; err: vhost_vdpa_host_notifiers_uninit(dev, i - dev->vq_index); + memory_region_transaction_commit(); return; }