Vsock uses buffers in order, and for tx driver doesn't have to
know the length of the buffer. So we can do a batch for vsock if
in order negotiated, only write one used ring for a batch of buffers
Signed-off-by: Guo Zhi <qtxuning1999@sjtu.edu.cn>
---
drivers/vhost/vsock.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index 368330417bde..e08fbbb5439e 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -497,7 +497,7 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
struct vhost_vsock *vsock = container_of(vq->dev, struct vhost_vsock,
dev);
struct virtio_vsock_pkt *pkt;
- int head, pkts = 0, total_len = 0;
+ int head, pkts = 0, total_len = 0, add = 0;
unsigned int out, in;
bool added = false;
@@ -551,10 +551,18 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
else
virtio_transport_free_pkt(pkt);
- vhost_add_used(vq, head, 0);
+ if (!vhost_has_feature(vq, VIRTIO_F_IN_ORDER)) {
+ vhost_add_used(vq, head, 0);
+ } else {
+ vq->heads[add].id = head;
+ vq->heads[add++].len = 0;
+ }
added = true;
} while(likely(!vhost_exceeds_weight(vq, ++pkts, total_len)));
+ /* If in order feature negotiaged, we can do a batch to increase performance */
+ if (vhost_has_feature(vq, VIRTIO_F_IN_ORDER) && added)
+ vhost_add_used_n(vq, vq->heads, add);
no_more_replies:
if (added)
vhost_signal(&vsock->dev, vq);
--
2.17.1
在 2022/9/1 13:54, Guo Zhi 写道:
> Vsock uses buffers in order, and for tx driver doesn't have to
> know the length of the buffer. So we can do a batch for vsock if
> in order negotiated, only write one used ring for a batch of buffers
>
> Signed-off-by: Guo Zhi <qtxuning1999@sjtu.edu.cn>
> ---
> drivers/vhost/vsock.c | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
> index 368330417bde..e08fbbb5439e 100644
> --- a/drivers/vhost/vsock.c
> +++ b/drivers/vhost/vsock.c
> @@ -497,7 +497,7 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
> struct vhost_vsock *vsock = container_of(vq->dev, struct vhost_vsock,
> dev);
> struct virtio_vsock_pkt *pkt;
> - int head, pkts = 0, total_len = 0;
> + int head, pkts = 0, total_len = 0, add = 0;
> unsigned int out, in;
> bool added = false;
>
> @@ -551,10 +551,18 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
> else
> virtio_transport_free_pkt(pkt);
>
> - vhost_add_used(vq, head, 0);
> + if (!vhost_has_feature(vq, VIRTIO_F_IN_ORDER)) {
> + vhost_add_used(vq, head, 0);
I'd do this step by step.
1) switch to use vhost_add_used_n() for vsock, less copy_to_user()
better performance
2) do in-order on top
> + } else {
> + vq->heads[add].id = head;
> + vq->heads[add++].len = 0;
How can we guarantee that we are in the boundary of the heads array?
Btw in the case of in-order we don't need to record the heads, instead
we just need to know the head of the last buffer, it reduces the stress
on the cache.
Thanks
> + }
> added = true;
> } while(likely(!vhost_exceeds_weight(vq, ++pkts, total_len)));
>
> + /* If in order feature negotiaged, we can do a batch to increase performance */
> + if (vhost_has_feature(vq, VIRTIO_F_IN_ORDER) && added)
> + vhost_add_used_n(vq, vq->heads, add);
> no_more_replies:
> if (added)
> vhost_signal(&vsock->dev, vq);
----- Original Message -----
> From: "jasowang" <jasowang@redhat.com>
> To: "Guo Zhi" <qtxuning1999@sjtu.edu.cn>, "eperezma" <eperezma@redhat.com>, "sgarzare" <sgarzare@redhat.com>, "Michael
> Tsirkin" <mst@redhat.com>
> Cc: "netdev" <netdev@vger.kernel.org>, "linux-kernel" <linux-kernel@vger.kernel.org>, "kvm list" <kvm@vger.kernel.org>,
> "virtualization" <virtualization@lists.linux-foundation.org>
> Sent: Wednesday, September 7, 2022 12:27:40 PM
> Subject: Re: [RFC v3 3/7] vsock: batch buffers in tx
> 在 2022/9/1 13:54, Guo Zhi 写道:
>> Vsock uses buffers in order, and for tx driver doesn't have to
>> know the length of the buffer. So we can do a batch for vsock if
>> in order negotiated, only write one used ring for a batch of buffers
>>
>> Signed-off-by: Guo Zhi <qtxuning1999@sjtu.edu.cn>
>> ---
>> drivers/vhost/vsock.c | 12 ++++++++++--
>> 1 file changed, 10 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
>> index 368330417bde..e08fbbb5439e 100644
>> --- a/drivers/vhost/vsock.c
>> +++ b/drivers/vhost/vsock.c
>> @@ -497,7 +497,7 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work
>> *work)
>> struct vhost_vsock *vsock = container_of(vq->dev, struct vhost_vsock,
>> dev);
>> struct virtio_vsock_pkt *pkt;
>> - int head, pkts = 0, total_len = 0;
>> + int head, pkts = 0, total_len = 0, add = 0;
>> unsigned int out, in;
>> bool added = false;
>>
>> @@ -551,10 +551,18 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work
>> *work)
>> else
>> virtio_transport_free_pkt(pkt);
>>
>> - vhost_add_used(vq, head, 0);
>> + if (!vhost_has_feature(vq, VIRTIO_F_IN_ORDER)) {
>> + vhost_add_used(vq, head, 0);
>
>
> I'd do this step by step.
>
> 1) switch to use vhost_add_used_n() for vsock, less copy_to_user()
> better performance
> 2) do in-order on top
>
>
LGTM!, I think it is the correct way.
>> + } else {
>> + vq->heads[add].id = head;
>> + vq->heads[add++].len = 0;
>
>
> How can we guarantee that we are in the boundary of the heads array?
>
> Btw in the case of in-order we don't need to record the heads, instead
> we just need to know the head of the last buffer, it reduces the stress
> on the cache.
>
> Thanks
>
Yeah, I will change this and only copy last head for in order feature.
Thanks
>
>> + }
>> added = true;
>> } while(likely(!vhost_exceeds_weight(vq, ++pkts, total_len)));
>>
>> + /* If in order feature negotiaged, we can do a batch to increase performance
>> */
>> + if (vhost_has_feature(vq, VIRTIO_F_IN_ORDER) && added)
>> + vhost_add_used_n(vq, vq->heads, add);
>> no_more_replies:
>> if (added)
>> vhost_signal(&vsock->dev, vq);
On Thu, Sep 1, 2022 at 7:55 AM Guo Zhi <qtxuning1999@sjtu.edu.cn> wrote:
>
> Vsock uses buffers in order, and for tx driver doesn't have to
> know the length of the buffer. So we can do a batch for vsock if
> in order negotiated, only write one used ring for a batch of buffers
>
> Signed-off-by: Guo Zhi <qtxuning1999@sjtu.edu.cn>
> ---
> drivers/vhost/vsock.c | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
> index 368330417bde..e08fbbb5439e 100644
> --- a/drivers/vhost/vsock.c
> +++ b/drivers/vhost/vsock.c
> @@ -497,7 +497,7 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
> struct vhost_vsock *vsock = container_of(vq->dev, struct vhost_vsock,
> dev);
> struct virtio_vsock_pkt *pkt;
> - int head, pkts = 0, total_len = 0;
> + int head, pkts = 0, total_len = 0, add = 0;
> unsigned int out, in;
> bool added = false;
>
> @@ -551,10 +551,18 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
> else
> virtio_transport_free_pkt(pkt);
>
> - vhost_add_used(vq, head, 0);
> + if (!vhost_has_feature(vq, VIRTIO_F_IN_ORDER)) {
> + vhost_add_used(vq, head, 0);
> + } else {
> + vq->heads[add].id = head;
> + vq->heads[add++].len = 0;
Knowing that the descriptors are used in order we can save a few
memory writes to the vq->heads[] array. vhost.c is checking for the
feature in_order anyway.
Thanks!
> + }
> added = true;
> } while(likely(!vhost_exceeds_weight(vq, ++pkts, total_len)));
>
> + /* If in order feature negotiaged, we can do a batch to increase performance */
> + if (vhost_has_feature(vq, VIRTIO_F_IN_ORDER) && added)
> + vhost_add_used_n(vq, vq->heads, add);
> no_more_replies:
> if (added)
> vhost_signal(&vsock->dev, vq);
> --
> 2.17.1
>
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