diff mbox series

[net-next,v3,2/5] net: add sysfs attribute to control napi threaded mode

Message ID 20201118191009.3406652-3-weiwan@google.com (mailing list archive)
State Changes Requested
Delegated to: Netdev Maintainers
Headers show
Series implement kthread based napi poll | expand

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netdev/stable success Stable not CCed

Commit Message

Wei Wang Nov. 18, 2020, 7:10 p.m. UTC 
From: Paolo Abeni <pabeni@redhat.com> 

this patch adds a new sysfs attribute to the network
device class. Said attribute is a bitmask that allows controlling
the threaded mode for all the napi instances of the given
network device.

The threaded mode can be switched only if related network device
is down.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: Wei Wang <weiwan@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
---
 net/core/net-sysfs.c | 103 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 103 insertions(+)

Comments

Randy Dunlap Nov. 18, 2020, 8:36 p.m. UTC | #1 
On 11/18/20 11:10 AM, Wei Wang wrote:
> From: Paolo Abeni <pabeni@redhat.com> 
> 
> this patch adds a new sysfs attribute to the network
> device class. Said attribute is a bitmask that allows controlling
> the threaded mode for all the napi instances of the given
> network device.
> 
> The threaded mode can be switched only if related network device
> is down.
> 
> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
> Signed-off-by: Wei Wang <weiwan@google.com>
> Reviewed-by: Eric Dumazet <edumazet@google.com>

Hi,

Could someone describe the bitmask (is it a bit per instance of the
network device?).
And how to use the sysfs interface, please?

> ---
>  net/core/net-sysfs.c | 103 +++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 103 insertions(+)
> 
> diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
> index 94fff0700bdd..df8dd25e5e4b 100644
> --- a/net/core/net-sysfs.c
> +++ b/net/core/net-sysfs.c


thanks.
Wei Wang Nov. 18, 2020, 9:20 p.m. UTC | #2 
On Wed, Nov 18, 2020 at 12:36 PM Randy Dunlap <rdunlap@infradead.org> wrote:
>
> On 11/18/20 11:10 AM, Wei Wang wrote:
> > From: Paolo Abeni <pabeni@redhat.com>
> >
> > this patch adds a new sysfs attribute to the network
> > device class. Said attribute is a bitmask that allows controlling
> > the threaded mode for all the napi instances of the given
> > network device.
> >
> > The threaded mode can be switched only if related network device
> > is down.
> >
> > Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> > Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
> > Signed-off-by: Wei Wang <weiwan@google.com>
> > Reviewed-by: Eric Dumazet <edumazet@google.com>
>
> Hi,
>
> Could someone describe the bitmask (is it a bit per instance of the
> network device?).
> And how to use the sysfs interface, please?
>

It is 1 bit per napi. Depending on the driver implementation, 1 napi
could correspond to 1 tx queue, or 1 rx queue, or 1 pair of tx/rx
queues.
To set bits in the bit mask, you could do:
echo 0-14 > /sys/class/net/<dev>/threaded
to set consecutive bits.
or:
echo 0,2,4,6,8 >  /sys/class/net/<dev>/threaded
to set individual bits.

To clear the bit mask, you could do:
echo > /sys/class/net/<dev>/threaded

> > ---
> >  net/core/net-sysfs.c | 103 +++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 103 insertions(+)
> >
> > diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
> > index 94fff0700bdd..df8dd25e5e4b 100644
> > --- a/net/core/net-sysfs.c
> > +++ b/net/core/net-sysfs.c
>
>
> thanks.
> --
> ~Randy
>
diff mbox series

Patch

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 94fff0700bdd..df8dd25e5e4b 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -538,6 +538,108 @@  static ssize_t phys_switch_id_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(phys_switch_id);
 
+static unsigned long *__alloc_thread_bitmap(struct net_device *netdev,
+					    int *bits)
+{
+	struct napi_struct *n;
+
+	*bits = 0;
+	list_for_each_entry(n, &netdev->napi_list, dev_list)
+		(*bits)++;
+
+	return kmalloc_array(BITS_TO_LONGS(*bits), sizeof(unsigned long),
+			     GFP_ATOMIC | __GFP_ZERO);
+}
+
+static ssize_t threaded_show(struct device *dev,
+			     struct device_attribute *attr, char *buf)
+{
+	struct net_device *netdev = to_net_dev(dev);
+	struct napi_struct *n;
+	unsigned long *bmap;
+	size_t count = 0;
+	int i, bits;
+
+	if (!rtnl_trylock())
+		return restart_syscall();
+
+	if (!dev_isalive(netdev))
+		goto unlock;
+
+	bmap = __alloc_thread_bitmap(netdev, &bits);
+	if (!bmap) {
+		count = -ENOMEM;
+		goto unlock;
+	}
+
+	i = 0;
+	list_for_each_entry(n, &netdev->napi_list, dev_list) {
+		if (test_bit(NAPI_STATE_THREADED, &n->state))
+			set_bit(i, bmap);
+		i++;
+	}
+
+	count = bitmap_print_to_pagebuf(true, buf, bmap, bits);
+	kfree(bmap);
+
+unlock:
+	rtnl_unlock();
+
+	return count;
+}
+
+static ssize_t threaded_store(struct device *dev,
+			      struct device_attribute *attr,
+			      const char *buf, size_t len)
+{
+	struct net_device *netdev = to_net_dev(dev);
+	struct napi_struct *n;
+	unsigned long *bmap;
+	int i, bits;
+	size_t ret;
+
+	if (!capable(CAP_NET_ADMIN))
+		return -EPERM;
+
+	if (!rtnl_trylock())
+		return restart_syscall();
+
+	if (!dev_isalive(netdev)) {
+		ret = len;
+		goto unlock;
+	}
+
+	if (netdev->flags & IFF_UP) {
+		ret = -EBUSY;
+		goto unlock;
+	}
+
+	bmap = __alloc_thread_bitmap(netdev, &bits);
+	if (!bmap) {
+		ret = -ENOMEM;
+		goto unlock;
+	}
+
+	ret = bitmap_parselist(buf, bmap, bits);
+	if (ret)
+		goto free_unlock;
+
+	i = 0;
+	list_for_each_entry(n, &netdev->napi_list, dev_list) {
+		napi_set_threaded(n, test_bit(i, bmap));
+		i++;
+	}
+	ret = len;
+
+free_unlock:
+	kfree(bmap);
+
+unlock:
+	rtnl_unlock();
+	return ret;
+}
+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 +672,7 @@  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);