Stefano Garzarella
2019-May-31 13:39 UTC
[PATCH v3 0/5] vsock/virtio: optimizations to increase the throughput
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
Stefano Garzarella
2019-May-31 13:39 UTC
[PATCH v3 1/5] vsock/virtio: limit the memory used per-socket
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 <sgarzare at redhat.com> --- 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
Stefano Garzarella
2019-May-31 13:39 UTC
[PATCH v3 2/5] vsock/virtio: fix locking for fwd_cnt and buf_alloc
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 <sgarzare at redhat.com> --- 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
Stefano Garzarella
2019-May-31 13:39 UTC
[PATCH v3 3/5] vsock/virtio: reduce credit update messages
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 <sgarzare at redhat.com> --- 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
Stefano Garzarella
2019-May-31 13:39 UTC
[PATCH v3 4/5] vhost/vsock: split packets to send using multiple buffers
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 <sgarzare at redhat.com> --- 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
Stefano Garzarella
2019-May-31 13:39 UTC
[PATCH v3 5/5] vsock/virtio: change the maximum packet size allowed
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 <sgarzare at redhat.com> --- 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
David Miller
2019-Jun-03 01:03 UTC
[PATCH v3 2/5] vsock/virtio: fix locking for fwd_cnt and buf_alloc
From: Stefano Garzarella <sgarzare at redhat.com> 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.
Stefan Hajnoczi
2019-Jun-10 13:44 UTC
[PATCH v3 1/5] vsock/virtio: limit the memory used per-socket
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 <sgarzare at redhat.com> > --- > 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 <stefanha at redhat.com> -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 488 bytes Desc: not available URL: <http://lists.linuxfoundation.org/pipermail/virtualization/attachments/20190610/0a3bee84/attachment.sig>