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Date: Mon, 12 Apr 2010 06:34:20 -0700
From: Tom Herbert <therbert@...gle.com>
To: Changli Gao <xiaosuo@...il.com>
Cc: "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH] rps: add flow director support
On Sun, Apr 11, 2010 at 2:42 PM, Changli Gao <xiaosuo@...il.com> wrote:
> add rps flow director support
>
> with rps flow director, users can do weighted packet dispatching among CPUs.
> For example, CPU0:CPU1 is 1:3 for eth0's rx-0:
>
"Flow director" is a misnomer here in that it has no per flow
awareness, that is what RFS provides. Please use a different name.
> localhost linux # echo 4 > /sys/class/net/eth0/queues/rx-0/rps_flows
> localhost linux # echo 0 > /sys/class/net/eth0/queues/rx-0/rps_flow_0
> localhost linux # echo 1 > /sys/class/net/eth0/queues/rx-0/rps_flow_1
> localhost linux # echo 1 > /sys/class/net/eth0/queues/rx-0/rps_flow_2
> localhost linux # echo 1 > /sys/class/net/eth0/queues/rx-0/rps_flow_3
>
It might be better to put this in its own directory and also do it per
CPU instead of hash entry. This should result in a lot fewer entries
and I'm not sure how you would deal with holes in the hash table for
unspecified entries. Also, it would be nice not to have to specify a
number of entries. Maybe something like:
localhost linux # echo 1 > /sys/class/net/eth0/queues/rx-0/rps_cpu_map/0
localhost linux # echo 3 > /sys/class/net/eth0/queues/rx-0/rps_cpu_map/1
To specify CPU 0 with weight 1, CPU 1 with weight 3.
> Signed-off-by: Changli Gao <xiaosuo@...il.com>
> ----
> net/core/net-sysfs.c | 176 +++++++++++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 172 insertions(+), 4 deletions(-)
> diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
> index 1e7fdd6..d904610 100644
> --- a/net/core/net-sysfs.c
> +++ b/net/core/net-sysfs.c
> @@ -511,6 +511,109 @@ static struct sysfs_ops rx_queue_sysfs_ops = {
> .store = rx_queue_attr_store,
> };
>
> +static DEFINE_MUTEX(rps_map_lock);
> +
> +static ssize_t show_rps_flow(struct netdev_rx_queue *queue,
> + struct rx_queue_attribute *attribute, char *buf)
> +{
> + unsigned long flowid;
> + struct rps_map *map;
> + u16 cpu;
> +
> + strict_strtoul(attribute->attr.name + strlen("rps_flow_"), 10, &flowid);
> + rcu_read_lock();
> + map = rcu_dereference(queue->rps_map);
> + if (map && flowid < map->len)
> + cpu = map->cpus[flowid];
> + else
> + cpu = 0;
> + rcu_read_unlock();
> + return sprintf(buf, "%hu\n", cpu);
> +}
> +
> +static ssize_t store_rps_flow(struct netdev_rx_queue *queue,
> + struct rx_queue_attribute *attribute,
> + const char *buf, size_t len)
> +{
> + unsigned long flowid, cpu;
> + struct rps_map *map;
> +
> + if (!capable(CAP_NET_ADMIN))
> + return -EPERM;
> +
> + if (strict_strtoul(buf, 0, &cpu))
> + return -EINVAL;
> + strict_strtoul(attribute->attr.name + strlen("rps_flow_"), 10, &flowid);
> +
> + mutex_lock(&rps_map_lock);
> + map = queue->rps_map;
> + if (map && flowid < map->len)
> + map->cpus[flowid] = cpu;
> + mutex_unlock(&rps_map_lock);
> +
> + return len;
> +}
> +
> +static struct rx_queue_attribute **rps_flow_attribute;
> +static int rps_flow_attribute_size;
> +
> +/* must be called with rps_map_lock locked */
> +static int update_rps_flow_files(struct kobject *kobj,
> + struct rps_map *old_map, struct rps_map *map)
> +{
> + int i;
> + int old_map_len = old_map ? old_map->len : 0;
> + int map_len = map ? map->len : 0;
> +
> + if (old_map_len >= map_len) {
> + for (i = map_len; i < old_map_len; i++)
> + sysfs_remove_file(kobj, &rps_flow_attribute[i]->attr);
> + return 0;
> + }
> +
> + if (map_len > rps_flow_attribute_size) {
> + struct rx_queue_attribute **attrs;
> + char name[sizeof("rps_flow_4294967295")];
> + char *pname;
> +
> + attrs = krealloc(rps_flow_attribute, map_len * sizeof(void *),
> + GFP_KERNEL);
> + if (attrs == NULL)
> + return -ENOMEM;
> + rps_flow_attribute = attrs;
> + for (i = rps_flow_attribute_size; i < map_len; i++) {
> + rps_flow_attribute[i] = kmalloc(sizeof(**attrs),
> + GFP_KERNEL);
> + if (rps_flow_attribute[i] == NULL)
> + break;
> + sprintf(name, "rps_flow_%d", i);
> + pname = kstrdup(name, GFP_KERNEL);
> + if (pname == NULL) {
> + kfree(rps_flow_attribute[i]);
> + break;
> + }
> + rps_flow_attribute[i]->attr.name = pname;
> + rps_flow_attribute[i]->attr.mode = S_IRUGO | S_IWUSR;
> + rps_flow_attribute[i]->show = show_rps_flow;
> + rps_flow_attribute[i]->store = store_rps_flow;
> + }
> + rps_flow_attribute_size = i;
> + if (i != map_len)
> + return -ENOMEM;
> + }
> +
> + for (i = old_map_len; i < map_len; i++) {
> + if (sysfs_create_file(kobj, &rps_flow_attribute[i]->attr)) {
> + while (--i >= old_map_len)
> + sysfs_remove_file(kobj,
> + &rps_flow_attribute[i]->attr);
> + return -ENOMEM;
> + }
> + }
> +
> + return 0;
> +}
> +
> static ssize_t show_rps_map(struct netdev_rx_queue *queue,
> struct rx_queue_attribute *attribute, char *buf)
> {
> @@ -555,7 +658,6 @@ ssize_t store_rps_map(struct netdev_rx_queue *queue,
> struct rps_map *old_map, *map;
> cpumask_var_t mask;
> int err, cpu, i;
> - static DEFINE_SPINLOCK(rps_map_lock);
>
> if (!capable(CAP_NET_ADMIN))
> return -EPERM;
> @@ -588,10 +690,15 @@ ssize_t store_rps_map(struct netdev_rx_queue *queue,
> map = NULL;
> }
>
> - spin_lock(&rps_map_lock);
> + mutex_lock(&rps_map_lock);
> old_map = queue->rps_map;
> - rcu_assign_pointer(queue->rps_map, map);
> - spin_unlock(&rps_map_lock);
> + err = update_rps_flow_files(&queue->kobj, old_map, map);
> + if (!err)
> + rcu_assign_pointer(queue->rps_map, map);
> + mutex_unlock(&rps_map_lock);
> +
> + if (err)
> + return err;
>
> if (old_map)
> call_rcu(&old_map->rcu, rps_map_release);
> @@ -603,8 +710,69 @@ ssize_t store_rps_map(struct netdev_rx_queue *queue,
> static struct rx_queue_attribute rps_cpus_attribute =
> __ATTR(rps_cpus, S_IRUGO | S_IWUSR, show_rps_map, store_rps_map);
>
> +static ssize_t show_rps_flows(struct netdev_rx_queue *queue,
> + struct rx_queue_attribute *attribute, char *buf)
> +{
> + struct rps_map *map;
> + unsigned int len;
> +
> + rcu_read_lock();
> + map = rcu_dereference(queue->rps_map);
> + len = map ? map->len : 0;
> + rcu_read_unlock();
> + return sprintf(buf, "%u\n", len);
> +}
> +
> +static ssize_t store_rps_flows(struct netdev_rx_queue *queue,
> + struct rx_queue_attribute *attribute,
> + const char *buf, size_t len)
> +{
> + struct rps_map *old_map, *map;
> + unsigned long flows;
> + int err;
> +
> + if (!capable(CAP_NET_ADMIN))
> + return -EPERM;
> +
> + if (strict_strtoul(buf, 0, &flows))
> + return -EINVAL;
> + if (flows != 0) {
> + map = kzalloc(max_t(unsigned, RPS_MAP_SIZE(flows),
> + L1_CACHE_BYTES), GFP_KERNEL);
> + if (map == NULL)
> + return -ENOMEM;
> + map->len = flows;
> + } else {
> + map = NULL;
> + }
> +
> + mutex_lock(&rps_map_lock);
> + old_map = queue->rps_map;
> + err = update_rps_flow_files(&queue->kobj, old_map, map);
> + if (!err) {
> + if (old_map && map)
> + memcpy(map->cpus, old_map->cpus,
> + sizeof(map->cpus[0]) *
> + min_t(unsigned int, flows, old_map->len));
> + rcu_assign_pointer(queue->rps_map, map);
> + }
> + mutex_unlock(&rps_map_lock);
> +
> + if (err)
> + return err;
> +
> + if (old_map)
> + call_rcu(&old_map->rcu, rps_map_release);
> +
> + return len;
> +}
> +
> +static struct rx_queue_attribute rps_flows_attribute =
> + __ATTR(rps_flows, S_IRUGO | S_IWUSR, show_rps_flows, store_rps_flows);
> +
> static struct attribute *rx_queue_default_attrs[] = {
> &rps_cpus_attribute.attr,
> + &rps_flows_attribute.attr,
> NULL
> };
>
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