178 lines
5.2 KiB
Diff
178 lines
5.2 KiB
Diff
From: Wei Wang <weiwan@google.com>
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Date: Mon, 8 Feb 2021 11:34:10 -0800
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Subject: [PATCH] net: add sysfs attribute to control napi threaded mode
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This patch adds a new sysfs attribute to the network device class.
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Said attribute provides a per-device control to enable/disable the
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threaded mode for all the napi instances of the given network device,
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without the need for a device up/down.
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User sets it to 1 or 0 to enable or disable threaded mode.
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Note: when switching between threaded and the current softirq based mode
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for a napi instance, it will not immediately take effect if the napi is
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currently being polled. The mode switch will happen for the next time
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napi_schedule() is called.
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Co-developed-by: Paolo Abeni <pabeni@redhat.com>
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Signed-off-by: Paolo Abeni <pabeni@redhat.com>
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Co-developed-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
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Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
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Co-developed-by: Felix Fietkau <nbd@nbd.name>
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Signed-off-by: Felix Fietkau <nbd@nbd.name>
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Signed-off-by: Wei Wang <weiwan@google.com>
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Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
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Signed-off-by: David S. Miller <davem@davemloft.net>
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---
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--- a/Documentation/ABI/testing/sysfs-class-net
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+++ b/Documentation/ABI/testing/sysfs-class-net
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@@ -337,3 +337,18 @@ Contact: netdev@vger.kernel.org
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Description:
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32-bit unsigned integer counting the number of times the link has
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been down
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+
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+What: /sys/class/net/<iface>/threaded
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+Date: Jan 2021
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+KernelVersion: 5.12
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+Contact: netdev@vger.kernel.org
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+Description:
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+ Boolean value to control the threaded mode per device. User could
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+ set this value to enable/disable threaded mode for all napi
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+ belonging to this device, without the need to do device up/down.
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+
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+ Possible values:
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+ == ==================================
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+ 0 threaded mode disabled for this dev
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+ 1 threaded mode enabled for this dev
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+ == ==================================
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--- a/include/linux/netdevice.h
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+++ b/include/linux/netdevice.h
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@@ -491,6 +491,8 @@ static inline bool napi_complete(struct
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return napi_complete_done(n, 0);
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}
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+int dev_set_threaded(struct net_device *dev, bool threaded);
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+
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/**
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* napi_disable - prevent NAPI from scheduling
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* @n: NAPI context
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--- a/net/core/dev.c
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+++ b/net/core/dev.c
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@@ -4298,8 +4298,9 @@ static inline void ____napi_schedule(str
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if (test_bit(NAPI_STATE_THREADED, &napi->state)) {
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/* Paired with smp_mb__before_atomic() in
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- * napi_enable(). Use READ_ONCE() to guarantee
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- * a complete read on napi->thread. Only call
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+ * napi_enable()/dev_set_threaded().
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+ * Use READ_ONCE() to guarantee a complete
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+ * read on napi->thread. Only call
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* wake_up_process() when it's not NULL.
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*/
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thread = READ_ONCE(napi->thread);
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@@ -6773,6 +6774,49 @@ static void init_gro_hash(struct napi_st
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napi->gro_bitmask = 0;
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}
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+int dev_set_threaded(struct net_device *dev, bool threaded)
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+{
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+ struct napi_struct *napi;
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+ int err = 0;
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+
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+ if (dev->threaded == threaded)
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+ return 0;
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+
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+ if (threaded) {
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+ list_for_each_entry(napi, &dev->napi_list, dev_list) {
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+ if (!napi->thread) {
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+ err = napi_kthread_create(napi);
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+ if (err) {
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+ threaded = false;
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+ break;
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+ }
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+ }
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+ }
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+ }
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+
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+ dev->threaded = threaded;
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+
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+ /* Make sure kthread is created before THREADED bit
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+ * is set.
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+ */
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+ smp_mb__before_atomic();
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+
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+ /* Setting/unsetting threaded mode on a napi might not immediately
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+ * take effect, if the current napi instance is actively being
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+ * polled. In this case, the switch between threaded mode and
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+ * softirq mode will happen in the next round of napi_schedule().
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+ * This should not cause hiccups/stalls to the live traffic.
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+ */
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+ list_for_each_entry(napi, &dev->napi_list, dev_list) {
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+ if (threaded)
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+ set_bit(NAPI_STATE_THREADED, &napi->state);
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+ else
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+ clear_bit(NAPI_STATE_THREADED, &napi->state);
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+ }
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+
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+ return err;
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+}
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+
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void netif_napi_add(struct net_device *dev, struct napi_struct *napi,
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int (*poll)(struct napi_struct *, int), int weight)
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{
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--- a/net/core/net-sysfs.c
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+++ b/net/core/net-sysfs.c
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@@ -587,6 +587,45 @@ static ssize_t phys_switch_id_show(struc
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}
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static DEVICE_ATTR_RO(phys_switch_id);
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+static ssize_t threaded_show(struct device *dev,
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+ struct device_attribute *attr, char *buf)
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+{
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+ struct net_device *netdev = to_net_dev(dev);
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+ ssize_t ret = -EINVAL;
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+
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+ if (!rtnl_trylock())
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+ return restart_syscall();
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+
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+ if (dev_isalive(netdev))
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+ ret = sprintf(buf, fmt_dec, netdev->threaded);
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+
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+ rtnl_unlock();
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+ return ret;
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+}
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+
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+static int modify_napi_threaded(struct net_device *dev, unsigned long val)
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+{
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+ int ret;
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+
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+ if (list_empty(&dev->napi_list))
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+ return -EOPNOTSUPP;
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+
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+ if (val != 0 && val != 1)
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+ return -EOPNOTSUPP;
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+
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+ ret = dev_set_threaded(dev, val);
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+
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+ return ret;
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+}
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+
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+static ssize_t threaded_store(struct device *dev,
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+ struct device_attribute *attr,
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+ const char *buf, size_t len)
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+{
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+ return netdev_store(dev, attr, buf, len, modify_napi_threaded);
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+}
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+static DEVICE_ATTR_RW(threaded);
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+
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static struct attribute *net_class_attrs[] __ro_after_init = {
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&dev_attr_netdev_group.attr,
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&dev_attr_type.attr,
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@@ -619,6 +658,7 @@ static struct attribute *net_class_attrs
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&dev_attr_proto_down.attr,
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&dev_attr_carrier_up_count.attr,
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&dev_attr_carrier_down_count.attr,
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+ &dev_attr_threaded.attr,
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NULL,
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};
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ATTRIBUTE_GROUPS(net_class);
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