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virtio: fix the out of order descriptors in tx

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Type: fix

Some vhost-backends give used descriptors back in
out-of-order. This patch fixes the native virtio to
handle out-of-order descriptors.

Change-Id: I74ba03a2111dc601be4396c0fa800c33db5554b4
Signed-off-by: Mohsin Kazmi <sykazmi@cisco.com>
(cherry picked from commit 7f6d145accc6e63b150ab4efc282f19cbe996b57)
This commit is contained in:
Mohsin Kazmi
2020-03-16 16:57:22 +00:00
parent 9ef52ab858
commit edef5b00ed
4 changed files with 103 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

104
src/vnet/devices/virtio/device.c
View File

@ -30,7 +30,8 @@
_(NO_FREE_SLOTS, "no free tx slots") \
_(TRUNC_PACKET, "packet > buffer size -- truncated in tx ring") \
_(PENDING_MSGS, "pending msgs in tx ring") \
_(NO_TX_QUEUES, "no tx queues")
_(NO_TX_QUEUES, "no tx queues") \
_(OUT_OF_ORDER, "out-of-order buffers in used ring")
typedef enum
{
@ -91,13 +92,31 @@ format_virtio_tx_trace (u8 * s, va_list * args)
}
static_always_inline void
virtio_free_used_device_desc (vlib_main_t * vm, virtio_vring_t * vring)
virtio_memset_ring_u32 (u32 * ring, u32 start, u32 ring_size, u32 n_buffers)
{
ASSERT (n_buffers <= ring_size);
if (PREDICT_TRUE (start + n_buffers <= ring_size))
{
clib_memset_u32 (ring + start, ~0, n_buffers);
}
else
{
clib_memset_u32 (ring + start, ~0, ring_size - start);
clib_memset_u32 (ring, ~0, n_buffers - (ring_size - start));
}
}
static_always_inline void
virtio_free_used_device_desc (vlib_main_t * vm, virtio_vring_t * vring,
uword node_index)
{
u16 used = vring->desc_in_use;
u16 sz = vring->size;
u16 mask = sz - 1;
u16 last = vring->last_used_idx;
u16 n_left = vring->used->idx - last;
u16 out_of_order_count = 0;
if (n_left == 0)
return;
@ -108,7 +127,7 @@ virtio_free_used_device_desc (vlib_main_t * vm, virtio_vring_t * vring)
u16 slot, n_buffers;
slot = n_buffers = e->id;
while (e->id == n_buffers)
while (e->id == (n_buffers & mask))
{
n_left--;
last++;
@ -119,18 +138,29 @@ virtio_free_used_device_desc (vlib_main_t * vm, virtio_vring_t * vring)
}
vlib_buffer_free_from_ring (vm, vring->buffers, slot,
sz, (n_buffers - slot));
virtio_memset_ring_u32 (vring->buffers, slot, sz, (n_buffers - slot));
used -= (n_buffers - slot);
if (n_left > 0)
{
slot = e->id;
vlib_buffer_free (vm, &vring->buffers[slot], 1);
vlib_buffer_free (vm, &vring->buffers[e->id], 1);
vring->buffers[e->id] = ~0;
used--;
last++;
n_left--;
out_of_order_count++;
vring->flags |= VRING_TX_OUT_OF_ORDER;
}
}
/*
* Some vhost-backends give buffers back in out-of-order fashion in used ring.
* It impacts the overall virtio-performance.
*/
if (out_of_order_count)
vlib_error_count (vm, node_index, VIRTIO_TX_ERROR_OUT_OF_ORDER,
out_of_order_count);
vring->desc_in_use = used;
vring->last_used_idx = last;
}
@ -263,6 +293,43 @@ add_buffer_to_slot (vlib_main_t * vm, virtio_if_t * vif,
return n_added;
}
static_always_inline u32
virtio_find_free_desc (virtio_vring_t * vring, u16 size, u16 mask,
u16 req, u16 next, u32 * first_free_desc_index,
u16 * free_desc_count)
{
u16 start = 0;
/* next is used as hint: from where to start looking */
for (u16 i = 0; i < size; i++, next++)
{
if (vring->buffers[next & mask] == ~0)
{
if (*first_free_desc_index == ~0)
{
*first_free_desc_index = (next & mask);
start = i;
(*free_desc_count)++;
req--;
if (req == 0)
break;
}
else
{
if (start + *free_desc_count == i)
{
(*free_desc_count)++;
req--;
if (req == 0)
break;
}
else
break;
}
}
}
return *first_free_desc_index;
}
static_always_inline uword
virtio_interface_tx_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
vlib_frame_t * frame, virtio_if_t * vif,
@ -275,6 +342,7 @@ virtio_interface_tx_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
u16 used, next, avail;
u16 sz = vring->size;
u16 mask = sz - 1;
u16 retry_count = 2;
u32 *buffers = vlib_frame_vector_args (frame);
clib_spinlock_lock_if_init (&vring->lockp);
@ -283,14 +351,30 @@ virtio_interface_tx_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
(vring->last_kick_avail_idx != vring->avail->idx))
virtio_kick (vm, vring, vif);
retry:
/* free consumed buffers */
virtio_free_used_device_desc (vm, vring);
virtio_free_used_device_desc (vm, vring, node->node_index);
used = vring->desc_in_use;
next = vring->desc_next;
avail = vring->avail->idx;
while (n_left && used < sz)
u16 free_desc_count = 0;
if (PREDICT_FALSE (vring->flags & VRING_TX_OUT_OF_ORDER))
{
u32 first_free_desc_index = ~0;
virtio_find_free_desc (vring, sz, mask, n_left, next,
&first_free_desc_index, &free_desc_count);
if (free_desc_count)
next = first_free_desc_index;
}
else
free_desc_count = sz - used;
while (n_left && free_desc_count)
{
u16 n_added = 0;
n_added =
@ -303,6 +387,7 @@ virtio_interface_tx_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
used += n_added;
buffers++;
n_left--;
free_desc_count--;
}
if (n_left != frame->n_vectors)
@ -317,6 +402,9 @@ virtio_interface_tx_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
if (n_left)
{
if (retry_count--)
goto retry;
vlib_error_count (vm, node->node_index, VIRTIO_TX_ERROR_NO_FREE_SLOTS,
n_left);
vlib_buffer_free (vm, buffers, n_left);

1
src/vnet/devices/virtio/pci.c
View File

@ -719,6 +719,7 @@ virtio_pci_vring_init (vlib_main_t * vm, virtio_if_t * vif, u16 queue_num)
{
virtio_log_debug (vim, vif, "tx-queue: number %u, size %u", queue_num,
queue_size);
clib_memset_u32 (vring->buffers, ~0, queue_size);
}
else
{

5
src/vnet/devices/virtio/virtio.c
View File

@ -117,6 +117,11 @@ virtio_vring_init (vlib_main_t * vm, virtio_if_t * vif, u16 idx, u16 sz)
ASSERT (vring->buffers == 0);
vec_validate_aligned (vring->buffers, sz, CLIB_CACHE_LINE_BYTES);
if (idx & 1)
{
clib_memset_u32 (vring->buffers, ~0, sz);
}
vring->size = sz;
vring->call_fd = eventfd (0, EFD_NONBLOCK | EFD_CLOEXEC);
vring->kick_fd = eventfd (0, EFD_CLOEXEC);

1
src/vnet/devices/virtio/virtio.h
View File

@ -112,6 +112,7 @@ typedef struct
u8 buffer_pool_index;
u16 size;
u16 queue_id;
#define VRING_TX_OUT_OF_ORDER 1
u16 flags;
u32 call_file_index;
u32 *buffers;