[RFC net-next v4 5/9] net: napi: Add napi_config

Joe Damato
2024-10-01T23:53:55Z

Add a persistent NAPI config area for NAPI configuration to the core.
Drivers opt-in to setting the persistent config for a NAPI by passing an
index when calling netif_napi_add_config.

napi_config is allocated in alloc_netdev_mqs, freed in free_netdev
(after the NAPIs are deleted).

Drivers which call netif_napi_add_config will have persistent per-NAPI
settings: NAPI IDs, gro_flush_timeout, and defer_hard_irq settings.

Per-NAPI settings are saved in napi_disable and restored in napi_enable.

Co-developed-by: Martin Karsten <mkarsten@uwaterloo.ca>
Signed-off-by: Martin Karsten <mkarsten@uwaterloo.ca>
Signed-off-by: Joe Damato <jdamato@fastly.com>
---
.../networking/net_cachelines/net_device.rst | 1 +
include/linux/netdevice.h | 32 ++++++++
net/core/dev.c | 79 +++++++++++++++++--
net/core/dev.h | 14 ++++
4 files changed, 119 insertions(+), 7 deletions(-)

diff --git a/Documentation/networking/net_cachelines/net_device.rst b/Documentation/networking/net_cachelines/net_device.rst
index 3d02ae79c850..11d659051f5e 100644
--- a/Documentation/networking/net_cachelines/net_device.rst
+++ b/Documentation/networking/net_cachelines/net_device.rst
@@ -183,3 +183,4 @@ struct hlist_head page_pools
struct dim_irq_moder* irq_moder
unsigned_long gro_flush_timeout
u32 napi_defer_hard_irqs
+struct napi_config* napi_config
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 33897edd16c8..51cff55e7ab8 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -342,6 +342,15 @@ struct gro_list {
*/
#define GRO_HASH_BUCKETS 8

+/*
+ * Structure for per-NAPI config
+ */
+struct napi_config {
+ u64 gro_flush_timeout;
+ u32 defer_hard_irqs;
+ unsigned int napi_id;
+};
+
/*
* Structure for NAPI scheduling similar to tasklet but with weighting
*/
@@ -379,6 +388,8 @@ struct napi_struct {
int irq;
unsigned long gro_flush_timeout;
u32 defer_hard_irqs;
+ int index;
+ struct napi_config *config;
};

enum {
@@ -2011,6 +2022,9 @@ enum netdev_reg_state {
* @dpll_pin: Pointer to the SyncE source pin of a DPLL subsystem,
* where the clock is recovered.
*
+ * @napi_config: An array of napi_config structures containing per-NAPI
+ * settings.
+ *
* FIXME: cleanup struct net_device such that network protocol info
* moves out.
*/
@@ -2400,6 +2414,7 @@ struct net_device {
struct dim_irq_moder *irq_moder;
unsigned long gro_flush_timeout;
u32 napi_defer_hard_irqs;
+ struct napi_config *napi_config;

u8 priv[] ____cacheline_aligned
__counted_by(priv_len);
@@ -2650,6 +2665,23 @@ netif_napi_add_tx_weight(struct net_device *dev,
netif_napi_add_weight(dev, napi, poll, weight);
}

+/**
+ * netif_napi_add_config - initialize a NAPI context with persistent config
+ * @dev: network device
+ * @napi: NAPI context
+ * @poll: polling function
+ * @weight: the poll weight of this NAPI
+ * @index: the NAPI index
+ */
+static inline void
+netif_napi_add_config(struct net_device *dev, struct napi_struct *napi,
+ int (*poll)(struct napi_struct *, int), int index)
+{
+ napi->index = index;
+ napi->config = &dev->napi_config[index];
+ netif_napi_add_weight(dev, napi, poll, NAPI_POLL_WEIGHT);
+}
+
/**
* netif_napi_add_tx() - initialize a NAPI context to be used for Tx only
* @dev: network device
diff --git a/net/core/dev.c b/net/core/dev.c
index 056ed44f766f..9acb6db19200 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6499,6 +6499,22 @@ EXPORT_SYMBOL(napi_busy_loop);

#endif /* CONFIG_NET_RX_BUSY_POLL */

+static void __napi_hash_add_with_id(struct napi_struct *napi,
+ unsigned int napi_id)
+{
+ napi->napi_id = napi_id;
+ hlist_add_head_rcu(&napi->napi_hash_node,
+ &napi_hash[napi->napi_id % HASH_SIZE(napi_hash)]);
+}
+
+static void napi_hash_add_with_id(struct napi_struct *napi,
+ unsigned int napi_id)
+{
+ spin_lock(&napi_hash_lock);
+ __napi_hash_add_with_id(napi, napi_id);
+ spin_unlock(&napi_hash_lock);
+}
+
static void napi_hash_add(struct napi_struct *napi)
{
if (test_bit(NAPI_STATE_NO_BUSY_POLL, &napi->state))
@@ -6511,10 +6527,8 @@ static void napi_hash_add(struct napi_struct *napi)
if (unlikely(++napi_gen_id < MIN_NAPI_ID))
napi_gen_id = MIN_NAPI_ID;
} while (napi_by_id(napi_gen_id));
- napi->napi_id = napi_gen_id;

- hlist_add_head_rcu(&napi->napi_hash_node,
- &napi_hash[napi->napi_id % HASH_SIZE(napi_hash)]);
+ __napi_hash_add_with_id(napi, napi_gen_id);

spin_unlock(&napi_hash_lock);
}
@@ -6637,6 +6651,28 @@ void netif_queue_set_napi(struct net_device *dev, unsigned int queue_index,
}
EXPORT_SYMBOL(netif_queue_set_napi);

+static void napi_restore_config(struct napi_struct *n)
+{
+ n->defer_hard_irqs = n->config->defer_hard_irqs;
+ n->gro_flush_timeout = n->config->gro_flush_timeout;
+ /* a NAPI ID might be stored in the config, if so use it. if not, use
+ * napi_hash_add to generate one for us. It will be saved to the config
+ * in napi_disable.
+ */
+ if (n->config->napi_id)
+ napi_hash_add_with_id(n, n->config->napi_id);
+ else
+ napi_hash_add(n);
+}
+
+static void napi_save_config(struct napi_struct *n)
+{
+ n->config->defer_hard_irqs = n->defer_hard_irqs;
+ n->config->gro_flush_timeout = n->gro_flush_timeout;
+ n->config->napi_id = n->napi_id;
+ napi_hash_del(n);
+}
+
void netif_napi_add_weight(struct net_device *dev, struct napi_struct *napi,
int (*poll)(struct napi_struct *, int), int weight)
{
@@ -6647,8 +6683,6 @@ void netif_napi_add_weight(struct net_device *dev, struct napi_struct *napi,
INIT_HLIST_NODE(&napi->napi_hash_node);
hrtimer_init(&napi->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_PINNED);
napi->timer.function = napi_watchdog;
- napi_set_defer_hard_irqs(napi, READ_ONCE(dev->napi_defer_hard_irqs));
- napi_set_gro_flush_timeout(napi, READ_ONCE(dev->gro_flush_timeout));
init_gro_hash(napi);
napi->skb = NULL;
INIT_LIST_HEAD(&napi->rx_list);
@@ -6666,7 +6700,13 @@ void netif_napi_add_weight(struct net_device *dev, struct napi_struct *napi,
set_bit(NAPI_STATE_SCHED, &napi->state);
set_bit(NAPI_STATE_NPSVC, &napi->state);
list_add_rcu(&napi->dev_list, &dev->napi_list);
- napi_hash_add(napi);
+
+ /* default settings from sysfs are applied to all NAPIs. any per-NAPI
+ * configuration will be loaded in napi_enable
+ */
+ napi_set_defer_hard_irqs(napi, READ_ONCE(dev->napi_defer_hard_irqs));
+ napi_set_gro_flush_timeout(napi, READ_ONCE(dev->gro_flush_timeout));
+
napi_get_frags_check(napi);
/* Create kthread for this napi if dev->threaded is set.
* Clear dev->threaded if kthread creation failed so that
@@ -6698,6 +6738,11 @@ void napi_disable(struct napi_struct *n)

hrtimer_cancel(&n->timer);

+ if (n->config)
+ napi_save_config(n);
+ else
+ napi_hash_del(n);
+
clear_bit(NAPI_STATE_DISABLE, &n->state);
}
EXPORT_SYMBOL(napi_disable);
@@ -6713,6 +6758,11 @@ void napi_enable(struct napi_struct *n)
{
unsigned long new, val = READ_ONCE(n->state);

+ if (n->config)
+ napi_restore_config(n);
+ else
+ napi_hash_add(n);
+
do {
BUG_ON(!test_bit(NAPI_STATE_SCHED, &val));

@@ -6742,7 +6792,11 @@ void __netif_napi_del(struct napi_struct *napi)
if (!test_and_clear_bit(NAPI_STATE_LISTED, &napi->state))
return;

- napi_hash_del(napi);
+ if (napi->config) {
+ napi->index = -1;
+ napi->config = NULL;
+ }
+
list_del_rcu(&napi->dev_list);
napi_free_frags(napi);

@@ -11079,6 +11133,8 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
unsigned int txqs, unsigned int rxqs)
{
struct net_device *dev;
+ size_t napi_config_sz;
+ unsigned int maxqs;

BUG_ON(strlen(name) >= sizeof(dev->name));

@@ -11092,6 +11148,8 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
return NULL;
}

+ maxqs = max(txqs, rxqs);
+
dev = kvzalloc(struct_size(dev, priv, sizeof_priv),
GFP_KERNEL_ACCOUNT | __GFP_RETRY_MAYFAIL);
if (!dev)
@@ -11166,6 +11224,11 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
if (!dev->ethtool)
goto free_all;

+ napi_config_sz = array_size(maxqs, sizeof(*dev->napi_config));
+ dev->napi_config = kvzalloc(napi_config_sz, GFP_KERNEL_ACCOUNT);
+ if (!dev->napi_config)
+ goto free_all;
+
strscpy(dev->name, name);
dev->name_assign_type = name_assign_type;
dev->group = INIT_NETDEV_GROUP;
@@ -11227,6 +11290,8 @@ void free_netdev(struct net_device *dev)
list_for_each_entry_safe(p, n, &dev->napi_list, dev_list)
netif_napi_del(p);

+ kvfree(dev->napi_config);
+
ref_tracker_dir_exit(&dev->refcnt_tracker);
#ifdef CONFIG_PCPU_DEV_REFCNT
free_percpu(dev->pcpu_refcnt);
diff --git a/net/core/dev.h b/net/core/dev.h
index 26e598aa56c3..7365fa0ffdc7 100644
--- a/net/core/dev.h
+++ b/net/core/dev.h
@@ -167,11 +167,18 @@ static inline void napi_set_defer_hard_irqs(struct napi_struct *n, u32 defer)
static inline void netdev_set_defer_hard_irqs(struct net_device *netdev,
u32 defer)
{
+ unsigned int count = max(netdev->num_rx_queues,
+ netdev->num_tx_queues);
struct napi_struct *napi;
+ int i;

WRITE_ONCE(netdev->napi_defer_hard_irqs, defer);
list_for_each_entry(napi, &netdev->napi_list, dev_list)
napi_set_defer_hard_irqs(napi, defer);
+
+ if (netdev->napi_config)
+ for (i = 0; i < count; i++)
+ netdev->napi_config[i].defer_hard_irqs = defer;
}

/**
@@ -207,11 +214,18 @@ static inline void napi_set_gro_flush_timeout(struct napi_struct *n,
static inline void netdev_set_gro_flush_timeout(struct net_device *netdev,
unsigned long timeout)
{
+ unsigned int count = max(netdev->num_rx_queues,
+ netdev->num_tx_queues);
struct napi_struct *napi;
+ int i;

WRITE_ONCE(netdev->gro_flush_timeout, timeout);
list_for_each_entry(napi, &netdev->napi_list, dev_list)
napi_set_gro_flush_timeout(napi, timeout);
+
+ if (netdev->napi_config)
+ for (i = 0; i < count; i++)
+ netdev->napi_config[i].gro_flush_timeout = timeout;
}

int rps_cpumask_housekeeping(struct cpumask *mask);
--
2.25.1