'vhost_id' is an array of 'PATH_MAX' bytes in the middle of
'netdev_dpdk' structure. That is 4K bytes.
'vhost_id' never used on a hot path and there is no need to keep
it inside the structure memory. Dynamic allocation will allow to
decrease 'struct netdev_dpdk' signigficantly, saving 4KB per ETH
port (ETH ports doesn't use 'vhost_id') and almost same value per
vhost ports (real 'vhost_id's, in common case, are much shorter).
We could save the pointer space by making the union with 'devargs'
which is mutually exclusive with 'vhost_id'.
As we're just removing the single 'PADDED_MEMBER', the total
cacheline layout is not affected.
Stats for 'struct netdev_dpdk':
Before: /* size: 4992, cachelines: 78 */
After : /* size: 896, cachelines: 14 */
Signed-off-by: Ilya Maximets <[email protected]>
---
lib/netdev-dpdk.c | 39 ++++++++++++++++++++++-----------------
1 file changed, 22 insertions(+), 17 deletions(-)
diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c
index 93d8e37bb..e5f9a9374 100644
--- a/lib/netdev-dpdk.c
+++ b/lib/netdev-dpdk.c
@@ -400,7 +400,12 @@ struct netdev_dpdk {
enum dpdk_dev_type type;
enum netdev_flags flags;
int link_reset_cnt;
- char *devargs; /* Device arguments for dpdk ports */
+ union {
+ /* Device arguments for dpdk ports */
+ char *devargs;
+ /* Identifier used to distinguish vhost devices from each other. */
+ char *vhost_id;
+ };
struct dpdk_tx_queue *tx_q;
struct rte_eth_link link;
);
@@ -417,11 +422,6 @@ struct netdev_dpdk {
/* 3 pad bytes here. */
);
- PADDED_MEMBERS(CACHE_LINE_SIZE,
- /* Identifier used to distinguish vhost devices from each other. */
- char vhost_id[PATH_MAX];
- );
-
PADDED_MEMBERS(CACHE_LINE_SIZE,
struct netdev up;
/* In dpdk_list. */
@@ -1276,8 +1276,7 @@ netdev_dpdk_vhost_construct(struct netdev *netdev)
/* Take the name of the vhost-user port and append it to the location where
* the socket is to be created, then register the socket.
*/
- snprintf(dev->vhost_id, sizeof dev->vhost_id, "%s/%s",
- dpdk_get_vhost_sock_dir(), name);
+ dev->vhost_id = xasprintf("%s/%s", dpdk_get_vhost_sock_dir(), name);
dev->vhost_driver_flags &= ~RTE_VHOST_USER_CLIENT;
err = rte_vhost_driver_register(dev->vhost_id, dev->vhost_driver_flags);
@@ -1323,6 +1322,11 @@ netdev_dpdk_vhost_construct(struct netdev *netdev)
}
out:
+ if (err) {
+ free(dev->vhost_id);
+ dev->vhost_id = NULL;
+ }
+
ovs_mutex_unlock(&dpdk_mutex);
VLOG_WARN_ONCE("dpdkvhostuser ports are considered deprecated; "
"please migrate to dpdkvhostuserclient ports.");
@@ -1451,13 +1455,14 @@ netdev_dpdk_vhost_destruct(struct netdev *netdev)
"socket '%s' must be restarted.", dev->vhost_id);
}
- vhost_id = xstrdup(dev->vhost_id);
+ vhost_id = dev->vhost_id;
+ dev->vhost_id = NULL;
common_destruct(dev);
ovs_mutex_unlock(&dpdk_mutex);
- if (!vhost_id[0]) {
+ if (!vhost_id) {
goto out;
}
@@ -1906,8 +1911,9 @@ netdev_dpdk_vhost_client_set_config(struct netdev *netdev,
ovs_mutex_lock(&dev->mutex);
if (!(dev->vhost_driver_flags & RTE_VHOST_USER_CLIENT)) {
path = smap_get(args, "vhost-server-path");
- if (path && strcmp(path, dev->vhost_id)) {
- strcpy(dev->vhost_id, path);
+ if (!nullable_string_is_equal(path, dev->vhost_id)) {
+ free(dev->vhost_id);
+ dev->vhost_id = nullable_xstrdup(path);
/* check zero copy configuration */
if (smap_get_bool(args, "dq-zero-copy", false)) {
dev->vhost_driver_flags |= RTE_VHOST_USER_DEQUEUE_ZERO_COPY;
@@ -3484,8 +3490,8 @@ new_device(int vid)
/* Add device to the vhost port with the same name as that passed down. */
LIST_FOR_EACH(dev, list_node, &dpdk_list) {
ovs_mutex_lock(&dev->mutex);
- if (strncmp(ifname, dev->vhost_id, IF_NAME_SZ) == 0) {
- uint32_t qp_num = rte_vhost_get_vring_num(vid)/VIRTIO_QNUM;
+ if (nullable_string_is_equal(ifname, dev->vhost_id)) {
+ uint32_t qp_num = rte_vhost_get_vring_num(vid) / VIRTIO_QNUM;
/* Get NUMA information */
newnode = rte_vhost_get_numa_node(vid);
@@ -3613,7 +3619,7 @@ vring_state_changed(int vid, uint16_t queue_id, int
enable)
ovs_mutex_lock(&dpdk_mutex);
LIST_FOR_EACH (dev, list_node, &dpdk_list) {
ovs_mutex_lock(&dev->mutex);
- if (strncmp(ifname, dev->vhost_id, IF_NAME_SZ) == 0) {
+ if (nullable_string_is_equal(ifname, dev->vhost_id)) {
if (enable) {
dev->tx_q[qid].map = qid;
} else {
@@ -4144,8 +4150,7 @@ netdev_dpdk_vhost_client_reconfigure(struct netdev
*netdev)
* 1. Device hasn't been registered yet.
* 2. A path has been specified.
*/
- if (!(dev->vhost_driver_flags & RTE_VHOST_USER_CLIENT)
- && strlen(dev->vhost_id)) {
+ if (!(dev->vhost_driver_flags & RTE_VHOST_USER_CLIENT) && dev->vhost_id) {
/* Register client-mode device. */
vhost_flags |= RTE_VHOST_USER_CLIENT;
--
2.17.1
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