From: Stefano Garzarella <sgarzare@redhat.com>
To: Arseniy Krasnov <avkrasnov@sberdevices.ru>
Cc: Stefan Hajnoczi <stefanha@redhat.com>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
Bobby Eshleman <bobby.eshleman@bytedance.com>,
kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel@sberdevices.ru, oxffffaa@gmail.com
Subject: Re: [RFC PATCH v3] virtio/vsock: allocate multiple skbuffs on tx
Date: Tue, 21 Mar 2023 09:40:02 +0100 [thread overview]
Message-ID: <20230321084002.5anjcr3ikw3ynbse@sgarzare-redhat> (raw)
In-Reply-To: <f33ef593-982e-2b3f-0986-6d537a3aaf08@sberdevices.ru>
On Tue, Mar 21, 2023 at 12:31:48AM +0300, Arseniy Krasnov wrote:
>This adds small optimization for tx path: instead of allocating single
>skbuff on every call to transport, allocate multiple skbuff's until
>credit space allows, thus trying to send as much as possible data without
>return to af_vsock.c.
>
>Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
>---
> Link to v1:
> https://lore.kernel.org/netdev/2c52aa26-8181-d37a-bccd-a86bd3cbc6e1@sberdevices.ru/
> Link to v2:
> https://lore.kernel.org/netdev/ea5725eb-6cb5-cf15-2938-34e335a442fa@sberdevices.ru/
>
> Changelog:
> v1 -> v2:
> - If sent something, return number of bytes sent (even in
> case of error). Return error only if failed to sent first
> skbuff.
>
> v2 -> v3:
> - Handle case when transport callback returns unexpected value which
> is not equal to 'skb->len'. Break loop.
> - Don't check for zero value of 'rest_len' before calling
> 'virtio_transport_put_credit()'. Decided to add this check directly
> to 'virtio_transport_put_credit()' in separate patch.
>
> net/vmw_vsock/virtio_transport_common.c | 59 +++++++++++++++++++------
> 1 file changed, 45 insertions(+), 14 deletions(-)
>
>diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>index 6564192e7f20..e0b2c6ecbe22 100644
>--- a/net/vmw_vsock/virtio_transport_common.c
>+++ b/net/vmw_vsock/virtio_transport_common.c
>@@ -196,7 +196,8 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
> const struct virtio_transport *t_ops;
> struct virtio_vsock_sock *vvs;
> u32 pkt_len = info->pkt_len;
>- struct sk_buff *skb;
>+ u32 rest_len;
>+ int ret;
>
> info->type = virtio_transport_get_type(sk_vsock(vsk));
>
>@@ -216,10 +217,6 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
>
> vvs = vsk->trans;
>
>- /* we can send less than pkt_len bytes */
>- if (pkt_len > VIRTIO_VSOCK_MAX_PKT_BUF_SIZE)
>- pkt_len = VIRTIO_VSOCK_MAX_PKT_BUF_SIZE;
>-
> /* virtio_transport_get_credit might return less than pkt_len credit */
> pkt_len = virtio_transport_get_credit(vvs, pkt_len);
>
>@@ -227,17 +224,51 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
> if (pkt_len == 0 && info->op == VIRTIO_VSOCK_OP_RW)
> return pkt_len;
>
>- skb = virtio_transport_alloc_skb(info, pkt_len,
>- src_cid, src_port,
>- dst_cid, dst_port);
>- if (!skb) {
>- virtio_transport_put_credit(vvs, pkt_len);
>- return -ENOMEM;
>- }
>+ ret = 0;
>+ rest_len = pkt_len;
>+
>+ do {
>+ struct sk_buff *skb;
>+ size_t skb_len;
>+
>+ skb_len = min_t(u32, VIRTIO_VSOCK_MAX_PKT_BUF_SIZE, rest_len);
>+
>+ skb = virtio_transport_alloc_skb(info, skb_len,
>+ src_cid, src_port,
>+ dst_cid, dst_port);
>+ if (!skb) {
>+ ret = -ENOMEM;
>+ break;
>+ }
>+
>+ virtio_transport_inc_tx_pkt(vvs, skb);
>
>- virtio_transport_inc_tx_pkt(vvs, skb);
>+ ret = t_ops->send_pkt(skb);
>
>- return t_ops->send_pkt(skb);
>+ if (ret < 0)
>+ break;
>+
>+ /* Both virtio and vhost 'send_pkt()' returns 'skb_len',
>+ * but for reliability use 'ret' instead of 'skb_len'.
>+ * Also if partial send happens (e.g. 'ret' != 'skb_len')
>+ * somehow, we break this loop, but account such returned
>+ * value in 'virtio_transport_put_credit()'.
>+ */
>+ rest_len -= ret;
>+
>+ if (ret != skb_len) {
>+ ret = -EFAULT;
Okay, but `ret` will be overwritten by the check we have before the
return ...
>+ break;
>+ }
>+ } while (rest_len);
>+
>+ virtio_transport_put_credit(vvs, rest_len);
>+
>+ /* Return number of bytes, if any data has been sent. */
>+ if (rest_len != pkt_len)
>+ ret = pkt_len - rest_len;
... here.
Since we don't expect this condition for now, perhaps we can avoid
setting ret with -EFAULT, but we can add a WARN_ONCE (interrupting the
loop as you did here).
This way we return the partial length as we did before.
Thanks,
Stefano
>+
>+ return ret;
> }
>
> static bool virtio_transport_inc_rx_pkt(struct virtio_vsock_sock *vvs,
>--
>2.25.1
>
next prev parent reply other threads:[~2023-03-21 8:41 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-20 21:31 [RFC PATCH v3] virtio/vsock: allocate multiple skbuffs on tx Arseniy Krasnov
2023-03-21 8:40 ` Stefano Garzarella [this message]
2023-03-21 10:36 ` Arseniy Krasnov
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