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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>
This commit is contained in:
Wei Wang 2021-02-08 11:34:10 -08:00 committed by David S. Miller
parent 29863d41bb
commit 5fdd2f0e5c
4 changed files with 103 additions and 2 deletions
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15
Documentation/ABI/testing/sysfs-class-net
View File

@ -337,3 +337,18 @@ 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
== ==================================

2
include/linux/netdevice.h
View File

@ -497,6 +497,8 @@ static inline bool napi_complete(struct napi_struct *n)
return napi_complete_done(n, 0);
}
int dev_set_threaded(struct net_device *dev, bool threaded);
/**
* napi_disable - prevent NAPI from scheduling
* @n: NAPI context

48
net/core/dev.c
View File

@ -4291,8 +4291,9 @@ static inline void ____napi_schedule(struct softnet_data *sd,
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);
@ -6738,6 +6739,49 @@ static void init_gro_hash(struct napi_struct *napi)
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)
{

40
net/core/net-sysfs.c
View File

@ -538,6 +538,45 @@ static ssize_t phys_switch_id_show(struct device *dev,
}
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,
@ -570,6 +609,7 @@ static struct attribute *net_class_attrs[] __ro_after_init = {
&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);