[RFC net-next v4 1/9] net: napi: Make napi_defer_hard_irqs per-NAPI

Joe Damato
2024-10-01T23:53:35Z

Add defer_hard_irqs to napi_struct in preparation for per-NAPI
settings.

The existing sysfs parameter is respected; writes to sysfs will write to
all NAPI structs for the device and the net_device defer_hard_irq field.
Reads from sysfs show the net_device field.

The ability to set defer_hard_irqs on specific NAPI instances will be
added in a later commit, via netdev-genl.

Signed-off-by: Joe Damato <jdamato@fastly.com>
---
.../networking/net_cachelines/net_device.rst | 2 +-
include/linux/netdevice.h | 3 +-
net/core/dev.c | 10 +++---
net/core/dev.h | 36 +++++++++++++++++++
net/core/net-sysfs.c | 2 +-
5 files changed, 45 insertions(+), 8 deletions(-)

diff --git a/Documentation/networking/net_cachelines/net_device.rst b/Documentation/networking/net_cachelines/net_device.rst
index 22b07c814f4a..eeeb7c925ec5 100644
--- a/Documentation/networking/net_cachelines/net_device.rst
+++ b/Documentation/networking/net_cachelines/net_device.rst
@@ -99,7 +99,6 @@ unsigned_int num_rx_queues
unsigned_int real_num_rx_queues - read_mostly get_rps_cpu
struct_bpf_prog* xdp_prog - read_mostly netif_elide_gro()
unsigned_long gro_flush_timeout - read_mostly napi_complete_done
-u32 napi_defer_hard_irqs - read_mostly napi_complete_done
unsigned_int gro_max_size - read_mostly skb_gro_receive
unsigned_int gro_ipv4_max_size - read_mostly skb_gro_receive
rx_handler_func_t* rx_handler read_mostly - __netif_receive_skb_core
@@ -183,3 +182,4 @@ struct_devlink_port* devlink_port
struct_dpll_pin* dpll_pin
struct hlist_head page_pools
struct dim_irq_moder* irq_moder
+u32 napi_defer_hard_irqs
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index e87b5e488325..55764efc5c93 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -377,6 +377,7 @@ struct napi_struct {
struct list_head dev_list;
struct hlist_node napi_hash_node;
int irq;
+ u32 defer_hard_irqs;
};

enum {
@@ -2075,7 +2076,6 @@ struct net_device {
unsigned int real_num_rx_queues;
struct netdev_rx_queue *_rx;
unsigned long gro_flush_timeout;
- u32 napi_defer_hard_irqs;
unsigned int gro_max_size;
unsigned int gro_ipv4_max_size;
rx_handler_func_t __rcu *rx_handler;
@@ -2398,6 +2398,7 @@ struct net_device {

/** @irq_moder: dim parameters used if IS_ENABLED(CONFIG_DIMLIB). */
struct dim_irq_moder *irq_moder;
+ u32 napi_defer_hard_irqs;

u8 priv[] ____cacheline_aligned
__counted_by(priv_len);
diff --git a/net/core/dev.c b/net/core/dev.c
index cd479f5f22f6..748739958d2a 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6227,7 +6227,7 @@ bool napi_complete_done(struct napi_struct *n, int work_done)
if (work_done) {
if (n->gro_bitmask)
timeout = READ_ONCE(n->dev->gro_flush_timeout);
- n->defer_hard_irqs_count = READ_ONCE(n->dev->napi_defer_hard_irqs);
+ n->defer_hard_irqs_count = napi_get_defer_hard_irqs(n);
}
if (n->defer_hard_irqs_count > 0) {
n->defer_hard_irqs_count--;
@@ -6365,7 +6365,7 @@ static void busy_poll_stop(struct napi_struct *napi, void *have_poll_lock,
bpf_net_ctx = bpf_net_ctx_set(&__bpf_net_ctx);

if (flags & NAPI_F_PREFER_BUSY_POLL) {
- napi->defer_hard_irqs_count = READ_ONCE(napi->dev->napi_defer_hard_irqs);
+ napi->defer_hard_irqs_count = napi_get_defer_hard_irqs(napi);
timeout = READ_ONCE(napi->dev->gro_flush_timeout);
if (napi->defer_hard_irqs_count && timeout) {
hrtimer_start(&napi->timer, ns_to_ktime(timeout), HRTIMER_MODE_REL_PINNED);
@@ -6647,6 +6647,7 @@ 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));
init_gro_hash(napi);
napi->skb = NULL;
INIT_LIST_HEAD(&napi->rx_list);
@@ -11053,7 +11054,7 @@ void netdev_sw_irq_coalesce_default_on(struct net_device *dev)

if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
dev->gro_flush_timeout = 20000;
- dev->napi_defer_hard_irqs = 1;
+ netdev_set_defer_hard_irqs(dev, 1);
}
}
EXPORT_SYMBOL_GPL(netdev_sw_irq_coalesce_default_on);
@@ -11991,7 +11992,6 @@ static void __init net_dev_struct_check(void)
CACHELINE_ASSERT_GROUP_MEMBER(struct net_device, net_device_read_rx, real_num_rx_queues);
CACHELINE_ASSERT_GROUP_MEMBER(struct net_device, net_device_read_rx, _rx);
CACHELINE_ASSERT_GROUP_MEMBER(struct net_device, net_device_read_rx, gro_flush_timeout);
- CACHELINE_ASSERT_GROUP_MEMBER(struct net_device, net_device_read_rx, napi_defer_hard_irqs);
CACHELINE_ASSERT_GROUP_MEMBER(struct net_device, net_device_read_rx, gro_max_size);
CACHELINE_ASSERT_GROUP_MEMBER(struct net_device, net_device_read_rx, gro_ipv4_max_size);
CACHELINE_ASSERT_GROUP_MEMBER(struct net_device, net_device_read_rx, rx_handler);
@@ -12003,7 +12003,7 @@ static void __init net_dev_struct_check(void)
#ifdef CONFIG_NET_XGRESS
CACHELINE_ASSERT_GROUP_MEMBER(struct net_device, net_device_read_rx, tcx_ingress);
#endif
- CACHELINE_ASSERT_GROUP_SIZE(struct net_device, net_device_read_rx, 104);
+ CACHELINE_ASSERT_GROUP_SIZE(struct net_device, net_device_read_rx, 100);
}

/*
diff --git a/net/core/dev.h b/net/core/dev.h
index 5654325c5b71..b3792219879b 100644
--- a/net/core/dev.h
+++ b/net/core/dev.h
@@ -138,6 +138,42 @@ static inline void netif_set_gro_ipv4_max_size(struct net_device *dev,
WRITE_ONCE(dev->gro_ipv4_max_size, size);
}

+/**
+ * napi_get_defer_hard_irqs - get the NAPI's defer_hard_irqs
+ * @n: napi struct to get the defer_hard_irqs field from
+ *
+ * Return: the per-NAPI value of the defar_hard_irqs field.
+ */
+static inline u32 napi_get_defer_hard_irqs(const struct napi_struct *n)
+{
+ return READ_ONCE(n->defer_hard_irqs);
+}
+
+/**
+ * napi_set_defer_hard_irqs - set the defer_hard_irqs for a napi
+ * @n: napi_struct to set the defer_hard_irqs field
+ * @defer: the value the field should be set to
+ */
+static inline void napi_set_defer_hard_irqs(struct napi_struct *n, u32 defer)
+{
+ WRITE_ONCE(n->defer_hard_irqs, defer);
+}
+
+/**
+ * netdev_set_defer_hard_irqs - set defer_hard_irqs for all NAPIs of a netdev
+ * @netdev: the net_device for which all NAPIs will have defer_hard_irqs set
+ * @defer: the defer_hard_irqs value to set
+ */
+static inline void netdev_set_defer_hard_irqs(struct net_device *netdev,
+ u32 defer)
+{
+ struct napi_struct *napi;
+
+ 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);
+}
+
int rps_cpumask_housekeeping(struct cpumask *mask);

#if defined(CONFIG_DEBUG_NET) && defined(CONFIG_BPF_SYSCALL)
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 05cf5347f25e..25125f356a15 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -429,7 +429,7 @@ static int change_napi_defer_hard_irqs(struct net_device *dev, unsigned long val
if (val > S32_MAX)
return -ERANGE;

- WRITE_ONCE(dev->napi_defer_hard_irqs, val);
+ netdev_set_defer_hard_irqs(dev, (u32)val);
return 0;
}

--
2.25.1