This series tries to increase the throughput of virtio-vsock with slight
changes.
While I was testing the v2 of this series I discovered an huge use of memory,
so I added patch 1 to mitigate this issue. I put it in this series in order
to better track the performance trends.
v3:
- Patch 1: added a threshold to copy only small packets [Jason]
- Patch 1: replaced the allocation of a new buffer with a copy of small packets
into the buffer of last packed queued. [Jason, Stefan]
- Removed 3 patches from the series:
- "[PATCH v2 2/8] vsock/virtio: free packets during the socket release"
Sent as a separate patch. It is already upstream.
- "[PATCH v2 7/8] vsock/virtio: increase RX buffer size to 64 KiB" and
"[PATCH v2 8/8] vsock/virtio: make the RX buffer size tunable"
As Jason suggested, we can do the 64KB buffer in the future with the
conversion of using skb.
- Patches 2, 3, 4, 5 are the same of v2 (change only the index since 2/8 was
sent as a separated patch)
v2: https://patchwork.kernel.org/cover/10938743
v1: https://patchwork.kernel.org/cover/10885431
Below are the benchmarks step by step. I used iperf3 [1] modified with VSOCK
support. As Micheal suggested in the v1, I booted host and guest with 'nosmap'.
I added two new rows with 32 and 128 bytes, to test small packets.
A brief description of patches:
- Patches 1: limit the memory usage with an extra copy for small packets
- Patches 2+3: fix locking and reduce the number of credit update messages
sent to the transmitter
- Patches 4+5: allow the host to split packets on multiple buffers and use
VIRTIO_VSOCK_MAX_PKT_BUF_SIZE as the max packet size allowed
host -> guest [Gbps]
pkt_size before opt p 1 p 2+3 p 4+5
32 0.035 0.032 0.049 0.051
64 0.069 0.061 0.123 0.126
128 0.138 0.116 0.256 0.252
256 0.247 0.254 0.434 0.444
512 0.498 0.482 0.940 0.931
1K 0.951 0.975 1.878 1.887
2K 1.882 1.872 3.735 3.720
4K 3.603 3.583 6.843 6.842
8K 5.881 5.761 11.841 12.057
16K 8.414 8.352 17.163 17.456
32K 14.020 13.926 19.156 20.883
64K 21.147 20.921 20.601 21.799
128K 21.098 21.027 21.145 23.596
256K 21.617 21.354 21.123 23.464
512K 20.967 21.056 21.236 23.775
guest -> host [Gbps]
pkt_size before opt p 1 p 2+3 p 4+5
32 0.044 0.043 0.059 0.058
64 0.090 0.086 0.110 0.109
128 0.176 0.166 0.217 0.219
256 0.342 0.335 0.431 0.435
512 0.674 0.664 0.843 0.883
1K 1.336 1.315 1.672 1.648
2K 2.613 2.615 3.163 3.173
4K 5.162 5.128 5.638 5.873
8K 8.479 8.913 10.787 10.236
16K 11.617 12.027 12.871 15.840
32K 11.234 11.074 11.643 24.385
64K 10.252 10.655 11.223 37.201
128K 10.101 10.219 10.346 39.340
256K 9.403 9.820 10.040 34.888
512K 8.822 9.911 10.410 34.562
As Stefan suggested in the v1, I measured also the efficiency in this way:
efficiency = Mbps / (%CPU_Host + %CPU_Guest)
The '%CPU_Guest' is taken inside the VM. I know that it is not the best way,
but it's provided for free from iperf3 and could be an indication.
host -> guest efficiency [Mbps / (%CPU_Host + %CPU_Guest)]
pkt_size before opt p 1 p 2+3 p 4+5
32 0.42 0.54 0.92 2.10
64 0.62 0.83 3.55 3.90
128 1.24 1.59 4.30 4.22
256 2.25 2.32 5.81 5.97
512 4.51 4.45 12.04 11.94
1K 8.70 8.93 23.10 23.33
2K 17.24 17.30 44.52 44.13
4K 33.01 32.97 82.45 81.65
8K 57.57 56.57 147.46 157.81
16K 82.36 81.97 214.60 253.35
32K 153.00 151.78 278.84 367.66
64K 236.54 246.02 301.18 454.15
128K 327.02 328.36 331.43 505.09
256K 336.23 331.09 330.05 515.09
512K 323.10 322.61 327.21 513.90
guest -> host efficiency [Mbps / (%CPU_Host + %CPU_Guest)]
pkt_size before opt p 1 p 2+3 p 4+5
32 0.42 0.42 0.60 0.606
64 0.86 0.84 1.20 1.187
128 1.69 1.64 2.38 2.393
256 3.31 3.31 4.67 4.723
512 6.50 6.56 9.19 9.454
1K 12.90 12.89 18.04 17.778
2K 25.45 25.92 34.31 34.028
4K 51.13 50.59 62.64 64.609
8K 95.81 100.98 112.95 113.105
16K 139.85 142.83 142.54 181.651
32K 147.43 146.66 146.86 286.545
64K 141.64 145.75 140.82 432.570
128K 148.30 148.87 143.89 490.037
256K 148.90 152.77 149.37 528.606
512K 140.68 153.65 152.64 516.622
[1] https://github.com/stefano-garzarella/iperf/
Stefano Garzarella (5):
vsock/virtio: limit the memory used per-socket
vsock/virtio: fix locking for fwd_cnt and buf_alloc
vsock/virtio: reduce credit update messages
vhost/vsock: split packets to send using multiple buffers
vsock/virtio: change the maximum packet size allowed
drivers/vhost/vsock.c | 53 ++++++++++---
include/linux/virtio_vsock.h | 4 +-
net/vmw_vsock/virtio_transport.c | 1 +
net/vmw_vsock/virtio_transport_common.c | 101 +++++++++++++++++++-----
4 files changed, 128 insertions(+), 31 deletions(-)
--
2.20.1
Since virtio-vsock was introduced, the buffers filled by the host
and pushed to the guest using the vring, are directly queued in
a per-socket list. These buffers are preallocated by the guest
with a fixed size (4 KB).
The maximum amount of memory used by each socket should be
controlled by the credit mechanism.
The default credit available per-socket is 256 KB, but if we use
only 1 byte per packet, the guest can queue up to 262144 of 4 KB
buffers, using up to 1 GB of memory per-socket. In addition, the
guest will continue to fill the vring with new 4 KB free buffers
to avoid starvation of other sockets.
This patch mitigates this issue copying the payload of small
packets (< 128 bytes) into the buffer of last packet queued, in
order to avoid wasting memory.
Signed-off-by: Stefano Garzarella <[email protected]>
---
drivers/vhost/vsock.c | 2 +
include/linux/virtio_vsock.h | 1 +
net/vmw_vsock/virtio_transport.c | 1 +
net/vmw_vsock/virtio_transport_common.c | 60 +++++++++++++++++++++----
4 files changed, 55 insertions(+), 9 deletions(-)
diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index bb5fc0e9fbc2..7964e2daee09 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -320,6 +320,8 @@ vhost_vsock_alloc_pkt(struct vhost_virtqueue *vq,
return NULL;
}
+ pkt->buf_len = pkt->len;
+
nbytes = copy_from_iter(pkt->buf, pkt->len, &iov_iter);
if (nbytes != pkt->len) {
vq_err(vq, "Expected %u byte payload, got %zu bytes\n",
diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
index e223e2632edd..7d973903f52e 100644
--- a/include/linux/virtio_vsock.h
+++ b/include/linux/virtio_vsock.h
@@ -52,6 +52,7 @@ struct virtio_vsock_pkt {
/* socket refcnt not held, only use for cancellation */
struct vsock_sock *vsk;
void *buf;
+ u32 buf_len;
u32 len;
u32 off;
bool reply;
diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
index 96ab344f17bb..beabb8025907 100644
--- a/net/vmw_vsock/virtio_transport.c
+++ b/net/vmw_vsock/virtio_transport.c
@@ -280,6 +280,7 @@ static void virtio_vsock_rx_fill(struct virtio_vsock *vsock)
break;
}
+ pkt->buf_len = buf_len;
pkt->len = buf_len;
sg_init_one(&hdr, &pkt->hdr, sizeof(pkt->hdr));
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index f3f3d06cb6d8..4fd4987511a9 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -27,6 +27,9 @@
/* How long to wait for graceful shutdown of a connection */
#define VSOCK_CLOSE_TIMEOUT (8 * HZ)
+/* Threshold for detecting small packets to copy */
+#define GOOD_COPY_LEN 128
+
static const struct virtio_transport *virtio_transport_get_ops(void)
{
const struct vsock_transport *t = vsock_core_get_transport();
@@ -65,6 +68,9 @@ virtio_transport_alloc_pkt(struct virtio_vsock_pkt_info *info,
pkt->buf = kmalloc(len, GFP_KERNEL);
if (!pkt->buf)
goto out_pkt;
+
+ pkt->buf_len = len;
+
err = memcpy_from_msg(pkt->buf, info->msg, len);
if (err)
goto out;
@@ -842,24 +848,60 @@ virtio_transport_recv_connecting(struct sock *sk,
return err;
}
+static void
+virtio_transport_recv_enqueue(struct vsock_sock *vsk,
+ struct virtio_vsock_pkt *pkt)
+{
+ struct virtio_vsock_sock *vvs = vsk->trans;
+ bool free_pkt = false;
+
+ pkt->len = le32_to_cpu(pkt->hdr.len);
+ pkt->off = 0;
+
+ spin_lock_bh(&vvs->rx_lock);
+
+ virtio_transport_inc_rx_pkt(vvs, pkt);
+
+ /* Try to copy small packets into the buffer of last packet queued,
+ * to avoid wasting memory queueing the entire buffer with a small
+ * payload.
+ */
+ if (pkt->len <= GOOD_COPY_LEN && !list_empty(&vvs->rx_queue)) {
+ struct virtio_vsock_pkt *last_pkt;
+
+ last_pkt = list_last_entry(&vvs->rx_queue,
+ struct virtio_vsock_pkt, list);
+
+ /* If there is space in the last packet queued, we copy the
+ * new packet in its buffer.
+ */
+ if (pkt->len <= last_pkt->buf_len - last_pkt->len) {
+ memcpy(last_pkt->buf + last_pkt->len, pkt->buf,
+ pkt->len);
+ last_pkt->len += pkt->len;
+ free_pkt = true;
+ goto out;
+ }
+ }
+
+ list_add_tail(&pkt->list, &vvs->rx_queue);
+
+out:
+ spin_unlock_bh(&vvs->rx_lock);
+ if (free_pkt)
+ virtio_transport_free_pkt(pkt);
+}
+
static int
virtio_transport_recv_connected(struct sock *sk,
struct virtio_vsock_pkt *pkt)
{
struct vsock_sock *vsk = vsock_sk(sk);
- struct virtio_vsock_sock *vvs = vsk->trans;
int err = 0;
switch (le16_to_cpu(pkt->hdr.op)) {
case VIRTIO_VSOCK_OP_RW:
- pkt->len = le32_to_cpu(pkt->hdr.len);
- pkt->off = 0;
-
- spin_lock_bh(&vvs->rx_lock);
- virtio_transport_inc_rx_pkt(vvs, pkt);
- list_add_tail(&pkt->list, &vvs->rx_queue);
- spin_unlock_bh(&vvs->rx_lock);
-
+ virtio_transport_recv_enqueue(vsk, pkt);
sk->sk_data_ready(sk);
return err;
case VIRTIO_VSOCK_OP_CREDIT_UPDATE:
--
2.20.1
fwd_cnt is written with rx_lock, so we should read it using
the same spinlock also if we are in the TX path.
Move also buf_alloc under rx_lock and add a missing locking
when we modify it.
Signed-off-by: Stefano Garzarella <[email protected]>
---
include/linux/virtio_vsock.h | 2 +-
net/vmw_vsock/virtio_transport_common.c | 6 ++++--
2 files changed, 5 insertions(+), 3 deletions(-)
diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
index 7d973903f52e..53703fe03681 100644
--- a/include/linux/virtio_vsock.h
+++ b/include/linux/virtio_vsock.h
@@ -35,11 +35,11 @@ struct virtio_vsock_sock {
/* Protected by tx_lock */
u32 tx_cnt;
- u32 buf_alloc;
u32 peer_fwd_cnt;
u32 peer_buf_alloc;
/* Protected by rx_lock */
+ u32 buf_alloc;
u32 fwd_cnt;
u32 rx_bytes;
struct list_head rx_queue;
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 4fd4987511a9..694d9805f989 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -211,10 +211,10 @@ static void virtio_transport_dec_rx_pkt(struct virtio_vsock_sock *vvs,
void virtio_transport_inc_tx_pkt(struct virtio_vsock_sock *vvs, struct virtio_vsock_pkt *pkt)
{
- spin_lock_bh(&vvs->tx_lock);
+ spin_lock_bh(&vvs->rx_lock);
pkt->hdr.fwd_cnt = cpu_to_le32(vvs->fwd_cnt);
pkt->hdr.buf_alloc = cpu_to_le32(vvs->buf_alloc);
- spin_unlock_bh(&vvs->tx_lock);
+ spin_unlock_bh(&vvs->rx_lock);
}
EXPORT_SYMBOL_GPL(virtio_transport_inc_tx_pkt);
@@ -434,7 +434,9 @@ void virtio_transport_set_buffer_size(struct vsock_sock *vsk, u64 val)
if (val > vvs->buf_size_max)
vvs->buf_size_max = val;
vvs->buf_size = val;
+ spin_lock_bh(&vvs->rx_lock);
vvs->buf_alloc = val;
+ spin_unlock_bh(&vvs->rx_lock);
}
EXPORT_SYMBOL_GPL(virtio_transport_set_buffer_size);
--
2.20.1
In order to reduce the number of credit update messages,
we send them only when the space available seen by the
transmitter is less than VIRTIO_VSOCK_MAX_PKT_BUF_SIZE.
Signed-off-by: Stefano Garzarella <[email protected]>
---
include/linux/virtio_vsock.h | 1 +
net/vmw_vsock/virtio_transport_common.c | 16 +++++++++++++---
2 files changed, 14 insertions(+), 3 deletions(-)
diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
index 53703fe03681..23396b996214 100644
--- a/include/linux/virtio_vsock.h
+++ b/include/linux/virtio_vsock.h
@@ -41,6 +41,7 @@ struct virtio_vsock_sock {
/* Protected by rx_lock */
u32 buf_alloc;
u32 fwd_cnt;
+ u32 last_fwd_cnt;
u32 rx_bytes;
struct list_head rx_queue;
};
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 694d9805f989..f7b0c4911308 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -212,6 +212,7 @@ static void virtio_transport_dec_rx_pkt(struct virtio_vsock_sock *vvs,
void virtio_transport_inc_tx_pkt(struct virtio_vsock_sock *vvs, struct virtio_vsock_pkt *pkt)
{
spin_lock_bh(&vvs->rx_lock);
+ vvs->last_fwd_cnt = vvs->fwd_cnt;
pkt->hdr.fwd_cnt = cpu_to_le32(vvs->fwd_cnt);
pkt->hdr.buf_alloc = cpu_to_le32(vvs->buf_alloc);
spin_unlock_bh(&vvs->rx_lock);
@@ -262,6 +263,7 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,
struct virtio_vsock_sock *vvs = vsk->trans;
struct virtio_vsock_pkt *pkt;
size_t bytes, total = 0;
+ u32 free_space;
int err = -EFAULT;
spin_lock_bh(&vvs->rx_lock);
@@ -292,11 +294,19 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,
virtio_transport_free_pkt(pkt);
}
}
+
+ free_space = vvs->buf_alloc - (vvs->fwd_cnt - vvs->last_fwd_cnt);
+
spin_unlock_bh(&vvs->rx_lock);
- /* Send a credit pkt to peer */
- virtio_transport_send_credit_update(vsk, VIRTIO_VSOCK_TYPE_STREAM,
- NULL);
+ /* We send a credit update only when the space available seen
+ * by the transmitter is less than VIRTIO_VSOCK_MAX_PKT_BUF_SIZE
+ */
+ if (free_space < VIRTIO_VSOCK_MAX_PKT_BUF_SIZE) {
+ virtio_transport_send_credit_update(vsk,
+ VIRTIO_VSOCK_TYPE_STREAM,
+ NULL);
+ }
return total;
--
2.20.1
Since now we are able to split packets, we can avoid limiting
their sizes to VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE.
Instead, we can use VIRTIO_VSOCK_MAX_PKT_BUF_SIZE as the max
packet size.
Signed-off-by: Stefano Garzarella <[email protected]>
---
net/vmw_vsock/virtio_transport_common.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index d192cb91cf25..b6ec6f81018b 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -182,8 +182,8 @@ 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_DEFAULT_RX_BUF_SIZE)
- pkt_len = VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE;
+ 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);
--
2.20.1
If the packets to sent to the guest are bigger than the buffer
available, we can split them, using multiple buffers and fixing
the length in the packet header.
This is safe since virtio-vsock supports only stream sockets.
Signed-off-by: Stefano Garzarella <[email protected]>
---
drivers/vhost/vsock.c | 51 +++++++++++++++++++------
net/vmw_vsock/virtio_transport_common.c | 15 ++++++--
2 files changed, 52 insertions(+), 14 deletions(-)
diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index 7964e2daee09..fb731d09f5f1 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -94,7 +94,7 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
struct iov_iter iov_iter;
unsigned out, in;
size_t nbytes;
- size_t len;
+ size_t iov_len, payload_len;
int head;
spin_lock_bh(&vsock->send_pkt_list_lock);
@@ -139,8 +139,24 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
break;
}
- len = iov_length(&vq->iov[out], in);
- iov_iter_init(&iov_iter, READ, &vq->iov[out], in, len);
+ iov_len = iov_length(&vq->iov[out], in);
+ if (iov_len < sizeof(pkt->hdr)) {
+ virtio_transport_free_pkt(pkt);
+ vq_err(vq, "Buffer len [%zu] too small\n", iov_len);
+ break;
+ }
+
+ iov_iter_init(&iov_iter, READ, &vq->iov[out], in, iov_len);
+ payload_len = pkt->len - pkt->off;
+
+ /* If the packet is greater than the space available in the
+ * buffer, we split it using multiple buffers.
+ */
+ if (payload_len > iov_len - sizeof(pkt->hdr))
+ payload_len = iov_len - sizeof(pkt->hdr);
+
+ /* Set the correct length in the header */
+ pkt->hdr.len = cpu_to_le32(payload_len);
nbytes = copy_to_iter(&pkt->hdr, sizeof(pkt->hdr), &iov_iter);
if (nbytes != sizeof(pkt->hdr)) {
@@ -149,16 +165,34 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
break;
}
- nbytes = copy_to_iter(pkt->buf, pkt->len, &iov_iter);
- if (nbytes != pkt->len) {
+ nbytes = copy_to_iter(pkt->buf + pkt->off, payload_len,
+ &iov_iter);
+ if (nbytes != payload_len) {
virtio_transport_free_pkt(pkt);
vq_err(vq, "Faulted on copying pkt buf\n");
break;
}
- vhost_add_used(vq, head, sizeof(pkt->hdr) + pkt->len);
+ vhost_add_used(vq, head, sizeof(pkt->hdr) + payload_len);
added = true;
+ /* Deliver to monitoring devices all correctly transmitted
+ * packets.
+ */
+ virtio_transport_deliver_tap_pkt(pkt);
+
+ pkt->off += payload_len;
+
+ /* If we didn't send all the payload we can requeue the packet
+ * to send it with the next available buffer.
+ */
+ if (pkt->off < pkt->len) {
+ spin_lock_bh(&vsock->send_pkt_list_lock);
+ list_add(&pkt->list, &vsock->send_pkt_list);
+ spin_unlock_bh(&vsock->send_pkt_list_lock);
+ continue;
+ }
+
if (pkt->reply) {
int val;
@@ -169,11 +203,6 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
restart_tx = true;
}
- /* Deliver to monitoring devices all correctly transmitted
- * packets.
- */
- virtio_transport_deliver_tap_pkt(pkt);
-
virtio_transport_free_pkt(pkt);
}
if (added)
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index f7b0c4911308..d192cb91cf25 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -98,8 +98,17 @@ static struct sk_buff *virtio_transport_build_skb(void *opaque)
struct virtio_vsock_pkt *pkt = opaque;
struct af_vsockmon_hdr *hdr;
struct sk_buff *skb;
+ size_t payload_len;
+ void *payload_buf;
- skb = alloc_skb(sizeof(*hdr) + sizeof(pkt->hdr) + pkt->len,
+ /* A packet could be split to fit the RX buffer, so we can retrieve
+ * the payload length from the header and the buffer pointer taking
+ * care of the offset in the original packet.
+ */
+ payload_len = le32_to_cpu(pkt->hdr.len);
+ payload_buf = pkt->buf + pkt->off;
+
+ skb = alloc_skb(sizeof(*hdr) + sizeof(pkt->hdr) + payload_len,
GFP_ATOMIC);
if (!skb)
return NULL;
@@ -139,8 +148,8 @@ static struct sk_buff *virtio_transport_build_skb(void *opaque)
skb_put_data(skb, &pkt->hdr, sizeof(pkt->hdr));
- if (pkt->len) {
- skb_put_data(skb, pkt->buf, pkt->len);
+ if (payload_len) {
+ skb_put_data(skb, payload_buf, payload_len);
}
return skb;
--
2.20.1
From: Stefano Garzarella <[email protected]>
Date: Fri, 31 May 2019 15:39:51 +0200
> @@ -434,7 +434,9 @@ void virtio_transport_set_buffer_size(struct vsock_sock *vsk, u64 val)
> if (val > vvs->buf_size_max)
> vvs->buf_size_max = val;
> vvs->buf_size = val;
> + spin_lock_bh(&vvs->rx_lock);
> vvs->buf_alloc = val;
> + spin_unlock_bh(&vvs->rx_lock);
This locking doesn't do anything other than to strongly order the
buf_size store to occur before the buf_alloc one.
If you need a memory barrier, use one.
On Sun, Jun 02, 2019 at 06:03:34PM -0700, David Miller wrote:
> From: Stefano Garzarella <[email protected]>
> Date: Fri, 31 May 2019 15:39:51 +0200
>
> > @@ -434,7 +434,9 @@ void virtio_transport_set_buffer_size(struct vsock_sock *vsk, u64 val)
> > if (val > vvs->buf_size_max)
> > vvs->buf_size_max = val;
> > vvs->buf_size = val;
> > + spin_lock_bh(&vvs->rx_lock);
> > vvs->buf_alloc = val;
> > + spin_unlock_bh(&vvs->rx_lock);
>
> This locking doesn't do anything other than to strongly order the
> buf_size store to occur before the buf_alloc one.
Sure, I'll remove the lock. I was confused because I moved its reading
under the rx_lock (together with other variables), but here I'm updating
only buf_alloc, so this lock is useless.
Thanks,
Stefano
On Fri, May 31, 2019 at 03:39:50PM +0200, Stefano Garzarella wrote:
> Since virtio-vsock was introduced, the buffers filled by the host
> and pushed to the guest using the vring, are directly queued in
> a per-socket list. These buffers are preallocated by the guest
> with a fixed size (4 KB).
>
> The maximum amount of memory used by each socket should be
> controlled by the credit mechanism.
> The default credit available per-socket is 256 KB, but if we use
> only 1 byte per packet, the guest can queue up to 262144 of 4 KB
> buffers, using up to 1 GB of memory per-socket. In addition, the
> guest will continue to fill the vring with new 4 KB free buffers
> to avoid starvation of other sockets.
>
> This patch mitigates this issue copying the payload of small
> packets (< 128 bytes) into the buffer of last packet queued, in
> order to avoid wasting memory.
>
> Signed-off-by: Stefano Garzarella <[email protected]>
> ---
> drivers/vhost/vsock.c | 2 +
> include/linux/virtio_vsock.h | 1 +
> net/vmw_vsock/virtio_transport.c | 1 +
> net/vmw_vsock/virtio_transport_common.c | 60 +++++++++++++++++++++----
> 4 files changed, 55 insertions(+), 9 deletions(-)
Reviewed-by: Stefan Hajnoczi <[email protected]>