From: Bobby Eshleman <[email protected]>
Every devmem dmabuf binding today hands the page_pool PAGE_SIZE niovs.
This caps a single RX descriptor at PAGE_SIZE, burning CPU on buffer
churn for large flows.
Add a bind-time netlink attribute, NETDEV_A_DMABUF_RX_BUF_SIZE, that
lets userspace request a larger niov size. The value must be a power of
two >= PAGE_SIZE.
Measurements
------------
Setup: kperf in devmem RX/TX cuda mode, 4 flows, 64 MB messages, 60s,
dctcp, num-rx-queues=4, dmabuf-rx/tx-size-mb=2048, 10 runs per niov
size, mlx5.
CPU Util:
niov net sirq % net idle % app sys % app idle %
----- ---------------- ---------------- ---------------- ----------------
4K 62.38 +/- 8.27 33.40 +/- 7.51 54.15 +/- 10.23 43.67 +/- 10.53
16K 58.91 +/- 5.35 35.23 +/- 5.88 41.05 +/- 8.87 56.42 +/- 9.24
32K 64.12 +/- 0.68 31.09 +/- 1.48 44.54 +/- 3.51 52.63 +/- 3.65
64K 54.69 +/- 5.54 39.67 +/- 5.81 35.47 +/- 3.11 61.97 +/- 3.27
RX app sys % drops ~19% from 4K to 64K.
Throughput:
niov RX dev Gbps RX flow avg Gbps
----- ---------------- -----------------
4K 300.63 +/- 53.21 75.16 +/- 13.30
16K 321.35 +/- 28.20 80.34 +/- 7.05
32K 347.63 +/- 2.20 86.91 +/- 0.55
64K 332.11 +/- 14.26 83.03 +/- 3.56
Throughput seems to increase, but the stdev is pretty wide so could just
be noise.
kperf support (not yet merged):
https://github.com/facebookexperimental/kperf/commit/8837577f920876bce6986ec18869ac04439ebcd2
Signed-off-by: Bobby Eshleman <[email protected]>
---
Documentation/netlink/specs/netdev.yaml | 8 +++++
include/uapi/linux/netdev.h | 1 +
net/core/devmem.c | 52 +++++++++++++++++++--------------
net/core/devmem.h | 13 ++++++---
net/core/netdev-genl-gen.c | 5 ++--
net/core/netdev-genl.c | 18 ++++++++++--
tools/include/uapi/linux/netdev.h | 1 +
7 files changed, 68 insertions(+), 30 deletions(-)
diff --git a/Documentation/netlink/specs/netdev.yaml
b/Documentation/netlink/specs/netdev.yaml
index a1f4c5a561e9..063119907983 100644
--- a/Documentation/netlink/specs/netdev.yaml
+++ b/Documentation/netlink/specs/netdev.yaml
@@ -591,6 +591,13 @@ attribute-sets:
type: u32
checks:
min: 1
+ -
+ name: rx-buf-size
+ doc: |
+ Size in bytes of each RX buffer the NIC writes into from the bound
+ dmabuf. Must be a power of two and >= PAGE_SIZE; defaults to
+ PAGE_SIZE.
+ type: u32
operations:
list:
@@ -805,6 +812,7 @@ operations:
- ifindex
- fd
- queues
+ - rx-buf-size
reply:
attributes:
- id
diff --git a/include/uapi/linux/netdev.h b/include/uapi/linux/netdev.h
index 7df1056a35fd..180a4ffffd60 100644
--- a/include/uapi/linux/netdev.h
+++ b/include/uapi/linux/netdev.h
@@ -217,6 +217,7 @@ enum {
NETDEV_A_DMABUF_QUEUES,
NETDEV_A_DMABUF_FD,
NETDEV_A_DMABUF_ID,
+ NETDEV_A_DMABUF_RX_BUF_SIZE,
__NETDEV_A_DMABUF_MAX,
NETDEV_A_DMABUF_MAX = (__NETDEV_A_DMABUF_MAX - 1)
diff --git a/net/core/devmem.c b/net/core/devmem.c
index 957d6b96216b..5a1c0d7984a8 100644
--- a/net/core/devmem.c
+++ b/net/core/devmem.c
@@ -46,7 +46,7 @@ static dma_addr_t net_devmem_get_dma_addr(const struct
net_iov *niov)
owner = net_devmem_iov_to_chunk_owner(niov);
return owner->base_dma_addr +
- ((dma_addr_t)net_iov_idx(niov) << PAGE_SHIFT);
+ ((dma_addr_t)net_iov_idx(niov) << owner->binding->niov_shift);
}
static void net_devmem_dmabuf_binding_release(struct percpu_ref *ref)
@@ -93,13 +93,14 @@ net_devmem_alloc_dmabuf(struct net_devmem_dmabuf_binding
*binding)
ssize_t offset;
ssize_t index;
- dma_addr = gen_pool_alloc_owner(binding->chunk_pool, PAGE_SIZE,
+ dma_addr = gen_pool_alloc_owner(binding->chunk_pool,
+ 1UL << binding->niov_shift,
(void **)&owner);
if (!dma_addr)
return NULL;
offset = dma_addr - owner->base_dma_addr;
- index = offset / PAGE_SIZE;
+ index = offset >> binding->niov_shift;
niov = &owner->area.niovs[index];
niov->desc.pp_magic = 0;
@@ -113,12 +114,13 @@ void net_devmem_free_dmabuf(struct net_iov *niov)
{
struct net_devmem_dmabuf_binding *binding =
net_devmem_iov_binding(niov);
unsigned long dma_addr = net_devmem_get_dma_addr(niov);
+ size_t niov_size = 1UL << binding->niov_shift;
if (WARN_ON(!gen_pool_has_addr(binding->chunk_pool, dma_addr,
- PAGE_SIZE)))
+ niov_size)))
return;
- gen_pool_free(binding->chunk_pool, dma_addr, PAGE_SIZE);
+ gen_pool_free(binding->chunk_pool, dma_addr, niov_size);
}
void net_devmem_unbind_dmabuf(struct net_devmem_dmabuf_binding *binding)
@@ -163,6 +165,9 @@ int net_devmem_bind_dmabuf_to_queue(struct net_device *dev,
u32 rxq_idx,
u32 xa_idx;
int err;
+ if (binding->niov_shift != PAGE_SHIFT)
+ mp_params.rx_page_size = 1U << binding->niov_shift;
+
err = netif_mp_open_rxq(dev, rxq_idx, &mp_params, extack);
if (err)
return err;
@@ -184,14 +189,16 @@ struct net_devmem_dmabuf_binding *
net_devmem_bind_dmabuf(struct net_device *dev, void *vdev,
struct device *dma_dev,
enum dma_data_direction direction,
- unsigned int dmabuf_fd, struct netdev_nl_sock *priv,
+ unsigned int dmabuf_fd, unsigned int niov_shift,
+ struct netdev_nl_sock *priv,
struct netlink_ext_ack *extack)
{
struct net_devmem_dmabuf_binding *binding;
+ size_t niov_size = 1UL << niov_shift;
static u32 id_alloc_next;
+ unsigned int sg_idx, i;
struct scatterlist *sg;
struct dma_buf *dmabuf;
- unsigned int sg_idx, i;
unsigned long virtual;
int err;
@@ -213,6 +220,7 @@ net_devmem_bind_dmabuf(struct net_device *dev, void *vdev,
binding->dev = dev;
binding->vdev = vdev;
+ binding->niov_shift = niov_shift;
xa_init_flags(&binding->bound_rxqs, XA_FLAGS_ALLOC);
err = percpu_ref_init(&binding->ref,
@@ -248,18 +256,14 @@ net_devmem_bind_dmabuf(struct net_device *dev, void *vdev,
goto err_unmap;
}
binding->tx_vec = kvmalloc_objs(struct net_iov *,
- dmabuf->size / PAGE_SIZE);
+ dmabuf->size >> niov_shift);
if (!binding->tx_vec) {
err = -ENOMEM;
goto err_unmap;
}
}
- /* For simplicity we expect to make PAGE_SIZE allocations, but the
- * binding can be much more flexible than that. We may be able to
- * allocate MTU sized chunks here. Leave that for future work...
- */
- binding->chunk_pool = gen_pool_create(PAGE_SHIFT,
+ binding->chunk_pool = gen_pool_create(niov_shift,
dev_to_node(&dev->dev));
if (!binding->chunk_pool) {
err = -ENOMEM;
@@ -273,9 +277,11 @@ net_devmem_bind_dmabuf(struct net_device *dev, void *vdev,
size_t len = sg_dma_len(sg);
struct net_iov *niov;
- if (!IS_ALIGNED(len, PAGE_SIZE)) {
+ if (!IS_ALIGNED(dma_addr, niov_size) ||
+ !IS_ALIGNED(len, niov_size)) {
err = -EINVAL;
- NL_SET_ERR_MSG(extack, "dma-buf SG length must be
PAGE_SIZE aligned");
+ NL_SET_ERR_MSG(extack,
+ "dmabuf sg entry not aligned to niov
size");
goto err_free_chunks;
}
@@ -288,7 +294,7 @@ net_devmem_bind_dmabuf(struct net_device *dev, void *vdev,
owner->area.base_virtual = virtual;
owner->base_dma_addr = dma_addr;
- owner->area.num_niovs = len / PAGE_SIZE;
+ owner->area.num_niovs = len >> niov_shift;
owner->binding = binding;
err = gen_pool_add_owner(binding->chunk_pool, dma_addr,
@@ -313,7 +319,7 @@ net_devmem_bind_dmabuf(struct net_device *dev, void *vdev,
page_pool_set_dma_addr_netmem(net_iov_to_netmem(niov),
net_devmem_get_dma_addr(niov));
if (direction == DMA_TO_DEVICE)
- binding->tx_vec[owner->area.base_virtual /
PAGE_SIZE + i] = niov;
+ binding->tx_vec[(owner->area.base_virtual >>
niov_shift) + i] = niov;
}
virtual += len;
@@ -430,13 +436,15 @@ struct net_iov *
net_devmem_get_niov_at(struct net_devmem_dmabuf_binding *binding,
size_t virt_addr, size_t *off, size_t *size)
{
+ size_t niov_size = 1UL << binding->niov_shift;
+
if (virt_addr >= binding->dmabuf->size)
return NULL;
- *off = virt_addr % PAGE_SIZE;
- *size = PAGE_SIZE - *off;
+ *off = virt_addr & (niov_size - 1);
+ *size = niov_size - *off;
- return binding->tx_vec[virt_addr / PAGE_SIZE];
+ return binding->tx_vec[virt_addr >> binding->niov_shift];
}
/*** "Dmabuf devmem memory provider" ***/
@@ -454,8 +462,8 @@ int mp_dmabuf_devmem_init(struct page_pool *pool)
pool->dma_sync = false;
pool->dma_sync_for_cpu = false;
- if (pool->p.order != 0)
- return -E2BIG;
+ if (pool->p.order != binding->niov_shift - PAGE_SHIFT)
+ return -EINVAL;
net_devmem_dmabuf_binding_get(binding);
return 0;
diff --git a/net/core/devmem.h b/net/core/devmem.h
index 3852a56036cb..4a293a7d1149 100644
--- a/net/core/devmem.h
+++ b/net/core/devmem.h
@@ -71,6 +71,8 @@ struct net_devmem_dmabuf_binding {
*/
struct net_iov **tx_vec;
+ unsigned int niov_shift;
+
struct work_struct unbind_w;
};
@@ -93,7 +95,8 @@ struct net_devmem_dmabuf_binding *
net_devmem_bind_dmabuf(struct net_device *dev, void *vdev,
struct device *dma_dev,
enum dma_data_direction direction,
- unsigned int dmabuf_fd, struct netdev_nl_sock *priv,
+ unsigned int dmabuf_fd, unsigned int niov_shift,
+ struct netdev_nl_sock *priv,
struct netlink_ext_ack *extack);
struct net_devmem_dmabuf_binding *net_devmem_lookup_dmabuf(u32 id);
void net_devmem_unbind_dmabuf(struct net_devmem_dmabuf_binding *binding);
@@ -122,10 +125,11 @@ static inline u32 net_devmem_iov_binding_id(const struct
net_iov *niov)
static inline unsigned long net_iov_virtual_addr(const struct net_iov *niov)
{
- struct net_iov_area *owner = net_iov_owner(niov);
+ struct dmabuf_genpool_chunk_owner *co =
+ net_devmem_iov_to_chunk_owner(niov);
- return owner->base_virtual +
- ((unsigned long)net_iov_idx(niov) << PAGE_SHIFT);
+ return net_iov_owner(niov)->base_virtual +
+ ((unsigned long)net_iov_idx(niov) << co->binding->niov_shift);
}
static inline bool
@@ -175,6 +179,7 @@ net_devmem_bind_dmabuf(struct net_device *dev, void *vdev,
struct device *dma_dev,
enum dma_data_direction direction,
unsigned int dmabuf_fd,
+ unsigned int niov_shift,
struct netdev_nl_sock *priv,
struct netlink_ext_ack *extack)
{
diff --git a/net/core/netdev-genl-gen.c b/net/core/netdev-genl-gen.c
index c7e138bfe345..55e03b9cd227 100644
--- a/net/core/netdev-genl-gen.c
+++ b/net/core/netdev-genl-gen.c
@@ -106,10 +106,11 @@ static const struct nla_policy
netdev_qstats_get_nl_policy[NETDEV_A_QSTATS_SCOPE
};
/* NETDEV_CMD_BIND_RX - do */
-static const struct nla_policy netdev_bind_rx_nl_policy[NETDEV_A_DMABUF_FD +
1] = {
+static const struct nla_policy
netdev_bind_rx_nl_policy[NETDEV_A_DMABUF_RX_BUF_SIZE + 1] = {
[NETDEV_A_DMABUF_IFINDEX] = NLA_POLICY_MIN(NLA_U32, 1),
[NETDEV_A_DMABUF_FD] = { .type = NLA_U32, },
[NETDEV_A_DMABUF_QUEUES] = NLA_POLICY_NESTED(netdev_queue_id_nl_policy),
+ [NETDEV_A_DMABUF_RX_BUF_SIZE] = { .type = NLA_U32, },
};
/* NETDEV_CMD_NAPI_SET - do */
@@ -219,7 +220,7 @@ static const struct genl_split_ops netdev_nl_ops[] = {
.cmd = NETDEV_CMD_BIND_RX,
.doit = netdev_nl_bind_rx_doit,
.policy = netdev_bind_rx_nl_policy,
- .maxattr = NETDEV_A_DMABUF_FD,
+ .maxattr = NETDEV_A_DMABUF_RX_BUF_SIZE,
.flags = GENL_ADMIN_PERM | GENL_CMD_CAP_DO,
},
{
diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
index b4d48f3672a5..9902a97698f5 100644
--- a/net/core/netdev-genl.c
+++ b/net/core/netdev-genl.c
@@ -1012,6 +1012,7 @@ int netdev_nl_bind_rx_doit(struct sk_buff *skb, struct
genl_info *info)
{
struct net_devmem_dmabuf_binding *binding;
u32 ifindex, dmabuf_fd, rxq_idx;
+ unsigned int niov_shift = PAGE_SHIFT;
struct netdev_nl_sock *priv;
struct net_device *netdev;
unsigned long *rxq_bitmap;
@@ -1028,6 +1029,18 @@ int netdev_nl_bind_rx_doit(struct sk_buff *skb, struct
genl_info *info)
ifindex = nla_get_u32(info->attrs[NETDEV_A_DEV_IFINDEX]);
dmabuf_fd = nla_get_u32(info->attrs[NETDEV_A_DMABUF_FD]);
+ if (info->attrs[NETDEV_A_DMABUF_RX_BUF_SIZE]) {
+ u32 rx_buf_size =
nla_get_u32(info->attrs[NETDEV_A_DMABUF_RX_BUF_SIZE]);
+
+ if (!rx_buf_size || !is_power_of_2(rx_buf_size) ||
+ rx_buf_size < PAGE_SIZE) {
+ NL_SET_ERR_MSG(info->extack,
+ "rx_buf_size must be a power of 2 >=
PAGE_SIZE");
+ return -EINVAL;
+ }
+ niov_shift = ilog2(rx_buf_size);
+ }
+
priv = genl_sk_priv_get(&netdev_nl_family, NETLINK_CB(skb).sk);
if (IS_ERR(priv))
return PTR_ERR(priv);
@@ -1078,7 +1091,8 @@ int netdev_nl_bind_rx_doit(struct sk_buff *skb, struct
genl_info *info)
}
binding = net_devmem_bind_dmabuf(netdev, NULL, dma_dev, DMA_FROM_DEVICE,
- dmabuf_fd, priv, info->extack);
+ dmabuf_fd, niov_shift, priv,
+ info->extack);
if (IS_ERR(binding)) {
err = PTR_ERR(binding);
goto err_rxq_bitmap;
@@ -1221,7 +1235,7 @@ int netdev_nl_bind_tx_doit(struct sk_buff *skb, struct
genl_info *info)
binding = net_devmem_bind_dmabuf(bind_dev,
bind_dev != netdev ? netdev : NULL,
dma_dev, DMA_TO_DEVICE, dmabuf_fd,
- priv, info->extack);
+ PAGE_SHIFT, priv, info->extack);
if (IS_ERR(binding)) {
err = PTR_ERR(binding);
goto err_unlock_bind_dev;
diff --git a/tools/include/uapi/linux/netdev.h
b/tools/include/uapi/linux/netdev.h
index 7df1056a35fd..180a4ffffd60 100644
--- a/tools/include/uapi/linux/netdev.h
+++ b/tools/include/uapi/linux/netdev.h
@@ -217,6 +217,7 @@ enum {
NETDEV_A_DMABUF_QUEUES,
NETDEV_A_DMABUF_FD,
NETDEV_A_DMABUF_ID,
+ NETDEV_A_DMABUF_RX_BUF_SIZE,
__NETDEV_A_DMABUF_MAX,
NETDEV_A_DMABUF_MAX = (__NETDEV_A_DMABUF_MAX - 1)
--
2.53.0-Meta
