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net: add napi_id and hash 

Adds a napi_id and a hashing mechanism to lookup a napi by id.
This will be used by subsequent patches to implement low latency
Ethernet device polling.
Based on a code sample by Eric Dumazet.

Signed-off-by: Eliezer Tamir <eliezer.tamir@linux.intel.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Tested-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eliezer Tamir 2013-06-10 11:39:41 +03:00 committed by David S. Miller
parent 6f00a02296
commit af12fa6e46
2 changed files with 88 additions and 0 deletions
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29
include/linux/netdevice.h
View File

@ -324,12 +324,15 @@ struct napi_struct {
struct sk_buff *gro_list;
struct sk_buff *skb;
struct list_head dev_list;
struct hlist_node napi_hash_node;
unsigned int napi_id;
};
enum {
NAPI_STATE_SCHED, /* Poll is scheduled */
NAPI_STATE_DISABLE, /* Disable pending */
NAPI_STATE_NPSVC, /* Netpoll - don't dequeue from poll_list */
NAPI_STATE_HASHED, /* In NAPI hash */
};
enum gro_result {
@ -445,6 +448,32 @@ static inline bool napi_reschedule(struct napi_struct *napi)
extern void __napi_complete(struct napi_struct *n);
extern void napi_complete(struct napi_struct *n);
/**
* napi_by_id - lookup a NAPI by napi_id
* @napi_id: hashed napi_id
*
* lookup @napi_id in napi_hash table
* must be called under rcu_read_lock()
*/
extern struct napi_struct *napi_by_id(unsigned int napi_id);
/**
* napi_hash_add - add a NAPI to global hashtable
* @napi: napi context
*
* generate a new napi_id and store a @napi under it in napi_hash
*/
extern void napi_hash_add(struct napi_struct *napi);
/**
* napi_hash_del - remove a NAPI from global table
* @napi: napi context
*
* Warning: caller must observe rcu grace period
* before freeing memory containing @napi
*/
extern void napi_hash_del(struct napi_struct *napi);
/**
* napi_disable - prevent NAPI from scheduling
* @n: napi context

59
net/core/dev.c
View File

@ -129,6 +129,7 @@
#include <linux/inetdevice.h>
#include <linux/cpu_rmap.h>
#include <linux/static_key.h>
#include <linux/hashtable.h>
#include "net-sysfs.h"
@ -166,6 +167,12 @@ static struct list_head offload_base __read_mostly;
DEFINE_RWLOCK(dev_base_lock);
EXPORT_SYMBOL(dev_base_lock);
/* protects napi_hash addition/deletion and napi_gen_id */
static DEFINE_SPINLOCK(napi_hash_lock);
static unsigned int napi_gen_id;
static DEFINE_HASHTABLE(napi_hash, 8);
seqcount_t devnet_rename_seq;
static inline void dev_base_seq_inc(struct net *net)
@ -4136,6 +4143,58 @@ void napi_complete(struct napi_struct *n)
}
EXPORT_SYMBOL(napi_complete);
/* must be called under rcu_read_lock(), as we dont take a reference */
struct napi_struct *napi_by_id(unsigned int napi_id)
{
unsigned int hash = napi_id % HASH_SIZE(napi_hash);
struct napi_struct *napi;
hlist_for_each_entry_rcu(napi, &napi_hash[hash], napi_hash_node)
if (napi->napi_id == napi_id)
return napi;
return NULL;
}
EXPORT_SYMBOL_GPL(napi_by_id);
void napi_hash_add(struct napi_struct *napi)
{
if (!test_and_set_bit(NAPI_STATE_HASHED, &napi->state)) {
spin_lock(&napi_hash_lock);
/* 0 is not a valid id, we also skip an id that is taken
* we expect both events to be extremely rare
*/
napi->napi_id = 0;
while (!napi->napi_id) {
napi->napi_id = ++napi_gen_id;
if (napi_by_id(napi->napi_id))
napi->napi_id = 0;
}
hlist_add_head_rcu(&napi->napi_hash_node,
&napi_hash[napi->napi_id % HASH_SIZE(napi_hash)]);
spin_unlock(&napi_hash_lock);
}
}
EXPORT_SYMBOL_GPL(napi_hash_add);
/* Warning : caller is responsible to make sure rcu grace period
* is respected before freeing memory containing @napi
*/
void napi_hash_del(struct napi_struct *napi)
{
spin_lock(&napi_hash_lock);
if (test_and_clear_bit(NAPI_STATE_HASHED, &napi->state))
hlist_del_rcu(&napi->napi_hash_node);
spin_unlock(&napi_hash_lock);
}
EXPORT_SYMBOL_GPL(napi_hash_del);
void netif_napi_add(struct net_device *dev, struct napi_struct *napi,
int (*poll)(struct napi_struct *, int), int weight)
{