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Date: Tue, 01 Dec 2015 14:13:34 -0800
From: Florian Fainelli <f.fainelli@...il.com>
To: kan.liang@...el.com, netdev@...r.kernel.org,
intel-wired-lan@...ts.osuosl.org, davem@...emloft.net
CC: jesse.brandeburg@...el.com, andi@...stfloor.org,
jeffrey.t.kirsher@...el.com, shannon.nelson@...el.com,
carolyn.wyborny@...el.com, donald.c.skidmore@...el.com,
matthew.vick@...el.com, john.ronciak@...el.com,
mitch.a.williams@...el.com, john.r.fastabend@...el.com,
ogerlitz@...lanox.com, edumazet@...gle.com, jiri@...lanox.com,
sfeldma@...il.com, gospo@...ulusnetworks.com,
sasha.levin@...cle.com, dsahern@...il.com, tj@...nel.org,
cascardo@...hat.com, corbet@....net
Subject: Re: [RFC 1/4] net: support per queue tx_usecs in sysfs
On 01/12/15 00:01, kan.liang@...el.com wrote:
> From: Kan Liang <kan.liang@...el.com>
>
> Network devices usually have many queues. Each queue has its own
> tx_usecs options. Currently, we can only set all the queues with same
> value by ethtool. This patch expose the tx_usecs in sysfs. So the user
> can set/get per queue coalesce parameter tx_usecs by sysfs.
The new interface you propose makes things inconsistent, since we have
two separate configuration paths (sysfs and ethtool), and it would seem
better to have per-queue awareness in ethtool, since there is a whole
bunch of other parameters that could be configured on a per-queue basis.
Have you tried to extend existing ethtool interfaces to cover the need
for multiple queues?
>
> Signed-off-by: Kan Liang <kan.liang@...el.com>
> ---
> Documentation/networking/scaling.txt | 12 ++++++++++++
> include/linux/netdevice.h | 8 ++++++++
> net/core/net-sysfs.c | 38 ++++++++++++++++++++++++++++++++++++
> 3 files changed, 58 insertions(+)
>
> diff --git a/Documentation/networking/scaling.txt b/Documentation/networking/scaling.txt
> index 59f4db2..636192d 100644
> --- a/Documentation/networking/scaling.txt
> +++ b/Documentation/networking/scaling.txt
> @@ -431,6 +431,18 @@ a max-rate attribute is supported, by setting a Mbps value to
>
> A value of zero means disabled, and this is the default.
>
> +Per Queue interrupt moderation:
> +=============================
> +
> +The interrupt moderation mechanism, which implemented by HW, employs
> +a series of timers to limit the number of interrupts it generates.
> +TX queue absolute delay timer can be set to a microseconds value with
> +
> +/sys/class/net/<dev>/queues/tx-<n>/tx_usecs
> +
> +For the device which doesn't support per queue interrupt moderation,
> +it shows "N/A".
> +
> Further Information
> ===================
> RPS and RFS were introduced in kernel 2.6.35. XPS was incorporated into
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 7d2d1d7..9db5c57 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -1059,6 +1059,10 @@ typedef u16 (*select_queue_fallback_t)(struct net_device *dev,
> * This function is used to get egress tunnel information for given skb.
> * This is useful for retrieving outer tunnel header parameters while
> * sampling packet.
> + * void (*ndo_set_per_queue_tx_usecs)(struct net_device *dev,
> + * int index, u32 val);
> + * void (*ndo_get_per_queue_tx_usecs)(struct net_device *dev, int index);
> + * This function is used to set/get per queue coalesce parameter tx_usecs.
> *
> */
> struct net_device_ops {
> @@ -1236,6 +1240,10 @@ struct net_device_ops {
> bool proto_down);
> int (*ndo_fill_metadata_dst)(struct net_device *dev,
> struct sk_buff *skb);
> + void (*ndo_set_per_queue_tx_usecs)(struct net_device *dev,
> + int index, u32 val);
> + u32 (*ndo_get_per_queue_tx_usecs)(struct net_device *dev,
> + int index);
> };
>
> /**
> diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
> index f88a62a..48016b8 100644
> --- a/net/core/net-sysfs.c
> +++ b/net/core/net-sysfs.c
> @@ -1239,12 +1239,50 @@ static struct netdev_queue_attribute xps_cpus_attribute =
> __ATTR(xps_cpus, S_IRUGO | S_IWUSR, show_xps_map, store_xps_map);
> #endif /* CONFIG_XPS */
>
> +static ssize_t tx_usecs_show(struct netdev_queue *queue,
> + struct netdev_queue_attribute *attr,
> + char *buf)
> +{
> + struct net_device *dev = queue->dev;
> + int index = queue - dev->_tx;
> + u32 val;
> +
> + if (dev->netdev_ops->ndo_get_per_queue_tx_usecs) {
> + val = dev->netdev_ops->ndo_get_per_queue_tx_usecs(dev, index);
> + return sprintf(buf, "%u\n", val);
> + }
> +
> + return sprintf(buf, "N/A\n");
> +}
> +
> +static ssize_t tx_usecs_store(struct netdev_queue *queue,
> + struct netdev_queue_attribute *attr,
> + const char *buf, size_t len)
> +{
> + struct net_device *dev = queue->dev;
> + int index = queue - dev->_tx;
> + u32 val, ret;
> +
> + ret = kstrtouint(buf, 0, &val);
> + if (ret < 0)
> + return -EINVAL;
> +
> + if (dev->netdev_ops->ndo_set_per_queue_tx_usecs)
> + dev->netdev_ops->ndo_set_per_queue_tx_usecs(dev, index, val);
> +
> + return len;
> +}
> +
> +static struct netdev_queue_attribute tx_usecs_attribute =
> + __ATTR(tx_usecs, S_IRUGO | S_IWUSR, tx_usecs_show, tx_usecs_store);
> +
> static struct attribute *netdev_queue_default_attrs[] = {
> &queue_trans_timeout.attr,
> #ifdef CONFIG_XPS
> &xps_cpus_attribute.attr,
> &queue_tx_maxrate.attr,
> #endif
> + &tx_usecs_attribute.attr,
> NULL
> };
>
>
--
Florian
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