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Message-Id: <20210204213117.1736289-4-weiwan@google.com>
Date: Thu, 4 Feb 2021 13:31:17 -0800
From: Wei Wang <weiwan@...gle.com>
To: David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
Jakub Kicinski <kuba@...nel.org>
Cc: Paolo Abeni <pabeni@...hat.com>,
Hannes Frederic Sowa <hannes@...essinduktion.org>,
Eric Dumazet <edumazet@...gle.com>,
Felix Fietkau <nbd@....name>,
Alexander Duyck <alexanderduyck@...com>
Subject: [PATCH net-next v10 3/3] 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@...hat.com>
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
Co-developed-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
Signed-off-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
Co-developed-by: Felix Fietkau <nbd@....name>
Signed-off-by: Felix Fietkau <nbd@....name>
Signed-off-by: Wei Wang <weiwan@...gle.com>
---
Documentation/ABI/testing/sysfs-class-net | 15 +++++
include/linux/netdevice.h | 2 +
net/core/dev.c | 67 ++++++++++++++++++++++-
net/core/net-sysfs.c | 45 +++++++++++++++
4 files changed, 127 insertions(+), 2 deletions(-)
diff --git a/Documentation/ABI/testing/sysfs-class-net b/Documentation/ABI/testing/sysfs-class-net
index 1f2002df5ba2..1419103d11f9 100644
--- a/Documentation/ABI/testing/sysfs-class-net
+++ b/Documentation/ABI/testing/sysfs-class-net
@@ -337,3 +337,18 @@ Contact: netdev@...r.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@...r.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
+ == ==================================
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 99fb4ec9573e..1340327f7abf 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -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
diff --git a/net/core/dev.c b/net/core/dev.c
index a8c5eca17074..9cc9b245419e 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4290,8 +4290,9 @@ 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()/napi_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);
@@ -6743,6 +6744,68 @@ static void init_gro_hash(struct napi_struct *napi)
napi->gro_bitmask = 0;
}
+/* 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.
+ */
+static int napi_set_threaded(struct napi_struct *n, bool threaded)
+{
+ int err = 0;
+
+ if (threaded == !!test_bit(NAPI_STATE_THREADED, &n->state))
+ return 0;
+
+ if (!threaded) {
+ clear_bit(NAPI_STATE_THREADED, &n->state);
+ return 0;
+ }
+
+ if (!n->thread) {
+ err = napi_kthread_create(n);
+ if (err)
+ return err;
+ }
+
+ /* Make sure kthread is created before THREADED bit
+ * is set.
+ */
+ smp_mb__before_atomic();
+ set_bit(NAPI_STATE_THREADED, &n->state);
+
+ return 0;
+}
+
+static void dev_disable_threaded_all(struct net_device *dev)
+{
+ struct napi_struct *napi;
+
+ list_for_each_entry(napi, &dev->napi_list, dev_list)
+ napi_set_threaded(napi, false);
+ dev->threaded = 0;
+}
+
+int dev_set_threaded(struct net_device *dev, bool threaded)
+{
+ struct napi_struct *napi;
+ int ret;
+
+ dev->threaded = threaded;
+ list_for_each_entry(napi, &dev->napi_list, dev_list) {
+ ret = napi_set_threaded(napi, threaded);
+ if (ret) {
+ /* Error occurred on one of the napi,
+ * reset threaded mode on all napi.
+ */
+ dev_disable_threaded_all(dev);
+ break;
+ }
+ }
+
+ return ret;
+}
+
void netif_napi_add(struct net_device *dev, struct napi_struct *napi,
int (*poll)(struct napi_struct *, int), int weight)
{
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index daf502c13d6d..969743567257 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -538,6 +538,50 @@ 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);
+ int ret;
+
+ if (!rtnl_trylock())
+ return restart_syscall();
+
+ if (!dev_isalive(netdev)) {
+ ret = -EINVAL;
+ goto unlock;
+ }
+
+ ret = sprintf(buf, fmt_dec, netdev->threaded);
+
+unlock:
+ 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 +614,7 @@ 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);
--
2.30.0.365.g02bc693789-goog
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