Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit af12fa6e authored by Eliezer Tamir's avatar Eliezer Tamir Committed by David S. Miller
Browse files

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: default avatarEliezer Tamir <eliezer.tamir@linux.intel.com>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Tested-by: default avatarWillem de Bruijn <willemb@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 6f00a022

include/linux/netdevice.h

+29 −0
Original line number Diff line number Diff line
@@ -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

net/core/dev.c

+59 −0
Original line number Diff line number Diff line
@@ -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)

{