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Message-ID: <20130603080117.18273.68908.stgit@ladj378.jer.intel.com>
Date: Mon, 03 Jun 2013 11:01:17 +0300
From: Eliezer Tamir <eliezer.tamir@...ux.intel.com>
To: David Miller <davem@...emloft.net>
Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
Jesse Brandeburg <jesse.brandeburg@...el.com>,
Don Skidmore <donald.c.skidmore@...el.com>,
e1000-devel@...ts.sourceforge.net,
Willem de Bruijn <willemb@...gle.com>,
Eric Dumazet <erdnetdev@...il.com>,
Ben Hutchings <bhutchings@...arflare.com>,
Andi Kleen <andi@...stfloor.org>, HPA <hpa@...or.com>,
Eilon Greenstien <eilong@...adcom.com>,
Or Gerlitz <or.gerlitz@...il.com>,
Alex Rosenbaum <alexr@...lanox.com>,
Eliezer Tamir <eliezer@...ir.org.il>
Subject: [PATCH v8 net-next 1/7] 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@...ux.intel.com>
---
include/linux/netdevice.h | 29 ++++++++++++++++++++++
net/core/dev.c | 59 +++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 88 insertions(+), 0 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 8f967e3..39bbd46 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -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 {
@@ -446,6 +449,32 @@ 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
*
diff --git a/net/core/dev.c b/net/core/dev.c
index d4d874a..f8388a0 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -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)
{
--
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