| From: Wei Wang <weiwan@google.com> |
| Date: Mon, 8 Feb 2021 11:34:10 -0800 |
| Subject: [PATCH] net: add sysfs attribute to control napi threaded mode |
| |
| This patch adds a new sysfs attribute to the network device class. |
| Said attribute provides a per-device control to enable/disable the |
| threaded mode for all the napi instances of the given network device, |
| without the need for a device up/down. |
| User sets it to 1 or 0 to enable or disable threaded mode. |
| Note: when switching between threaded and the current softirq based mode |
| for a napi instance, it will not immediately take effect if the napi is |
| currently being polled. The mode switch will happen for the next time |
| napi_schedule() is called. |
| |
| Co-developed-by: Paolo Abeni <pabeni@redhat.com> |
| Signed-off-by: Paolo Abeni <pabeni@redhat.com> |
| Co-developed-by: Hannes Frederic Sowa <hannes@stressinduktion.org> |
| Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org> |
| Co-developed-by: Felix Fietkau <nbd@nbd.name> |
| Signed-off-by: Felix Fietkau <nbd@nbd.name> |
| Signed-off-by: Wei Wang <weiwan@google.com> |
| Reviewed-by: Alexander Duyck <alexanderduyck@fb.com> |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| --- |
| |
| --- a/Documentation/ABI/testing/sysfs-class-net |
| +++ b/Documentation/ABI/testing/sysfs-class-net |
| @@ -301,3 +301,18 @@ Contact: netdev@vger.kernel.org |
| Description: |
| 32-bit unsigned integer counting the number of times the link has |
| been down |
| + |
| +What: /sys/class/net/<iface>/threaded |
| +Date: Jan 2021 |
| +KernelVersion: 5.12 |
| +Contact: netdev@vger.kernel.org |
| +Description: |
| + Boolean value to control the threaded mode per device. User could |
| + set this value to enable/disable threaded mode for all napi |
| + belonging to this device, without the need to do device up/down. |
| + |
| + Possible values: |
| + == ================================== |
| + 0 threaded mode disabled for this dev |
| + 1 threaded mode enabled for this dev |
| + == ================================== |
| --- a/include/linux/netdevice.h |
| +++ b/include/linux/netdevice.h |
| @@ -507,6 +507,8 @@ static inline bool napi_complete(struct |
| */ |
| bool napi_hash_del(struct napi_struct *napi); |
| |
| +int dev_set_threaded(struct net_device *dev, bool threaded); |
| + |
| /** |
| * napi_disable - prevent NAPI from scheduling |
| * @n: NAPI context |
| --- a/net/core/dev.c |
| +++ b/net/core/dev.c |
| @@ -3917,8 +3917,9 @@ static inline void ____napi_schedule(str |
| |
| if (test_bit(NAPI_STATE_THREADED, &napi->state)) { |
| /* Paired with smp_mb__before_atomic() in |
| - * napi_enable(). Use READ_ONCE() to guarantee |
| - * a complete read on napi->thread. Only call |
| + * napi_enable()/dev_set_threaded(). |
| + * Use READ_ONCE() to guarantee a complete |
| + * read on napi->thread. Only call |
| * wake_up_process() when it's not NULL. |
| */ |
| thread = READ_ONCE(napi->thread); |
| @@ -6296,6 +6297,49 @@ static void init_gro_hash(struct napi_st |
| napi->gro_bitmask = 0; |
| } |
| |
| +int dev_set_threaded(struct net_device *dev, bool threaded) |
| +{ |
| + struct napi_struct *napi; |
| + int err = 0; |
| + |
| + if (dev->threaded == threaded) |
| + return 0; |
| + |
| + if (threaded) { |
| + list_for_each_entry(napi, &dev->napi_list, dev_list) { |
| + if (!napi->thread) { |
| + err = napi_kthread_create(napi); |
| + if (err) { |
| + threaded = false; |
| + break; |
| + } |
| + } |
| + } |
| + } |
| + |
| + dev->threaded = threaded; |
| + |
| + /* Make sure kthread is created before THREADED bit |
| + * is set. |
| + */ |
| + smp_mb__before_atomic(); |
| + |
| + /* Setting/unsetting threaded mode on a napi might not immediately |
| + * take effect, if the current napi instance is actively being |
| + * polled. In this case, the switch between threaded mode and |
| + * softirq mode will happen in the next round of napi_schedule(). |
| + * This should not cause hiccups/stalls to the live traffic. |
| + */ |
| + list_for_each_entry(napi, &dev->napi_list, dev_list) { |
| + if (threaded) |
| + set_bit(NAPI_STATE_THREADED, &napi->state); |
| + else |
| + clear_bit(NAPI_STATE_THREADED, &napi->state); |
| + } |
| + |
| + return err; |
| +} |
| + |
| void netif_napi_add(struct net_device *dev, struct napi_struct *napi, |
| int (*poll)(struct napi_struct *, int), int weight) |
| { |
| --- a/net/core/net-sysfs.c |
| +++ b/net/core/net-sysfs.c |
| @@ -557,6 +557,45 @@ static ssize_t phys_switch_id_show(struc |
| } |
| static DEVICE_ATTR_RO(phys_switch_id); |
| |
| +static ssize_t threaded_show(struct device *dev, |
| + struct device_attribute *attr, char *buf) |
| +{ |
| + struct net_device *netdev = to_net_dev(dev); |
| + ssize_t ret = -EINVAL; |
| + |
| + if (!rtnl_trylock()) |
| + return restart_syscall(); |
| + |
| + if (dev_isalive(netdev)) |
| + ret = sprintf(buf, fmt_dec, netdev->threaded); |
| + |
| + rtnl_unlock(); |
| + return ret; |
| +} |
| + |
| +static int modify_napi_threaded(struct net_device *dev, unsigned long val) |
| +{ |
| + int ret; |
| + |
| + if (list_empty(&dev->napi_list)) |
| + return -EOPNOTSUPP; |
| + |
| + if (val != 0 && val != 1) |
| + return -EOPNOTSUPP; |
| + |
| + ret = dev_set_threaded(dev, val); |
| + |
| + return ret; |
| +} |
| + |
| +static ssize_t threaded_store(struct device *dev, |
| + struct device_attribute *attr, |
| + const char *buf, size_t len) |
| +{ |
| + return netdev_store(dev, attr, buf, len, modify_napi_threaded); |
| +} |
| +static DEVICE_ATTR_RW(threaded); |
| + |
| static struct attribute *net_class_attrs[] __ro_after_init = { |
| &dev_attr_netdev_group.attr, |
| &dev_attr_type.attr, |
| @@ -587,6 +626,7 @@ static struct attribute *net_class_attrs |
| &dev_attr_proto_down.attr, |
| &dev_attr_carrier_up_count.attr, |
| &dev_attr_carrier_down_count.attr, |
| + &dev_attr_threaded.attr, |
| NULL, |
| }; |
| ATTRIBUTE_GROUPS(net_class); |