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udp: dynamically size hash tables at boot time
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UDP_HTABLE_SIZE was initialy defined to 128, which is a bit small for
several setups.

4000 active UDP sockets -> 32 sockets per chain in average. An
incoming frame has to lookup all sockets to find best match, so long
chains hurt latency.

Instead of a fixed size hash table that cant be perfect for every
needs, let UDP stack choose its table size at boot time like tcp/ip
route, using alloc_large_system_hash() helper

Add an optional boot parameter, uhash_entries=x so that an admin can
force a size between 256 and 65536 if needed, like thash_entries and
rhash_entries.

dmesg logs two new lines :
[    0.647039] UDP hash table entries: 512 (order: 0, 4096 bytes)
[    0.647099] UDP Lite hash table entries: 512 (order: 0, 4096 bytes)

Maximal size on 64bit arches would be 65536 slots, ie 1 MBytes for non
debugging spinlocks.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Eric Dumazet authored and David S. Miller committed Oct 8, 2009
1 parent 8a6dfd4 commit f86dcc5
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Showing 6 changed files with 87 additions and 36 deletions.
3 changes: 3 additions & 0 deletions Documentation/kernel-parameters.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -2589,6 +2589,9 @@ and is between 256 and 4096 characters. It is defined in the file
uart6850= [HW,OSS]
Format: <io>,<irq>

uhash_entries= [KNL,NET]
Set number of hash buckets for UDP/UDP-Lite connections

uhci-hcd.ignore_oc=
[USB] Ignore overcurrent events (default N).
Some badly-designed motherboards generate lots of
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6 changes: 3 additions & 3 deletions include/linux/udp.h
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Original file line number Diff line number Diff line change
Expand Up @@ -45,11 +45,11 @@ static inline struct udphdr *udp_hdr(const struct sk_buff *skb)
return (struct udphdr *)skb_transport_header(skb);
}

#define UDP_HTABLE_SIZE 128
#define UDP_HTABLE_SIZE_MIN (CONFIG_BASE_SMALL ? 128 : 256)

static inline int udp_hashfn(struct net *net, const unsigned num)
static inline int udp_hashfn(struct net *net, unsigned num, unsigned mask)
{
return (num + net_hash_mix(net)) & (UDP_HTABLE_SIZE - 1);
return (num + net_hash_mix(net)) & mask;
}

struct udp_sock {
Expand Down
13 changes: 10 additions & 3 deletions include/net/udp.h
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Original file line number Diff line number Diff line change
Expand Up @@ -54,12 +54,19 @@ struct udp_hslot {
struct hlist_nulls_head head;
spinlock_t lock;
} __attribute__((aligned(2 * sizeof(long))));

struct udp_table {
struct udp_hslot hash[UDP_HTABLE_SIZE];
struct udp_hslot *hash;
unsigned int mask;
unsigned int log;
};
extern struct udp_table udp_table;
extern void udp_table_init(struct udp_table *);

extern void udp_table_init(struct udp_table *, const char *);
static inline struct udp_hslot *udp_hashslot(struct udp_table *table,
struct net *net, unsigned num)
{
return &table->hash[udp_hashfn(net, num, table->mask)];
}

/* Note: this must match 'valbool' in sock_setsockopt */
#define UDP_CSUM_NOXMIT 1
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91 changes: 66 additions & 25 deletions net/ipv4/udp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -106,7 +106,7 @@
#include <net/xfrm.h>
#include "udp_impl.h"

struct udp_table udp_table;
struct udp_table udp_table __read_mostly;
EXPORT_SYMBOL(udp_table);

int sysctl_udp_mem[3] __read_mostly;
Expand All @@ -121,14 +121,16 @@ EXPORT_SYMBOL(sysctl_udp_wmem_min);
atomic_t udp_memory_allocated;
EXPORT_SYMBOL(udp_memory_allocated);

#define PORTS_PER_CHAIN (65536 / UDP_HTABLE_SIZE)
#define MAX_UDP_PORTS 65536
#define PORTS_PER_CHAIN (MAX_UDP_PORTS / UDP_HTABLE_SIZE_MIN)

static int udp_lib_lport_inuse(struct net *net, __u16 num,
const struct udp_hslot *hslot,
unsigned long *bitmap,
struct sock *sk,
int (*saddr_comp)(const struct sock *sk1,
const struct sock *sk2))
const struct sock *sk2),
unsigned int log)
{
struct sock *sk2;
struct hlist_nulls_node *node;
Expand All @@ -142,8 +144,7 @@ static int udp_lib_lport_inuse(struct net *net, __u16 num,
|| sk2->sk_bound_dev_if == sk->sk_bound_dev_if) &&
(*saddr_comp)(sk, sk2)) {
if (bitmap)
__set_bit(sk2->sk_hash / UDP_HTABLE_SIZE,
bitmap);
__set_bit(sk2->sk_hash >> log, bitmap);
else
return 1;
}
Expand Down Expand Up @@ -180,13 +181,15 @@ int udp_lib_get_port(struct sock *sk, unsigned short snum,
/*
* force rand to be an odd multiple of UDP_HTABLE_SIZE
*/
rand = (rand | 1) * UDP_HTABLE_SIZE;
for (last = first + UDP_HTABLE_SIZE; first != last; first++) {
hslot = &udptable->hash[udp_hashfn(net, first)];
rand = (rand | 1) * (udptable->mask + 1);
for (last = first + udptable->mask + 1;
first != last;
first++) {
hslot = udp_hashslot(udptable, net, first);
bitmap_zero(bitmap, PORTS_PER_CHAIN);
spin_lock_bh(&hslot->lock);
udp_lib_lport_inuse(net, snum, hslot, bitmap, sk,
saddr_comp);
saddr_comp, udptable->log);

snum = first;
/*
Expand All @@ -196,17 +199,18 @@ int udp_lib_get_port(struct sock *sk, unsigned short snum,
*/
do {
if (low <= snum && snum <= high &&
!test_bit(snum / UDP_HTABLE_SIZE, bitmap))
!test_bit(snum >> udptable->log, bitmap))
goto found;
snum += rand;
} while (snum != first);
spin_unlock_bh(&hslot->lock);
}
goto fail;
} else {
hslot = &udptable->hash[udp_hashfn(net, snum)];
hslot = udp_hashslot(udptable, net, snum);
spin_lock_bh(&hslot->lock);
if (udp_lib_lport_inuse(net, snum, hslot, NULL, sk, saddr_comp))
if (udp_lib_lport_inuse(net, snum, hslot, NULL, sk,
saddr_comp, 0))
goto fail_unlock;
}
found:
Expand Down Expand Up @@ -283,7 +287,7 @@ static struct sock *__udp4_lib_lookup(struct net *net, __be32 saddr,
struct sock *sk, *result;
struct hlist_nulls_node *node;
unsigned short hnum = ntohs(dport);
unsigned int hash = udp_hashfn(net, hnum);
unsigned int hash = udp_hashfn(net, hnum, udptable->mask);
struct udp_hslot *hslot = &udptable->hash[hash];
int score, badness;

Expand Down Expand Up @@ -1013,8 +1017,8 @@ void udp_lib_unhash(struct sock *sk)
{
if (sk_hashed(sk)) {
struct udp_table *udptable = sk->sk_prot->h.udp_table;
unsigned int hash = udp_hashfn(sock_net(sk), sk->sk_hash);
struct udp_hslot *hslot = &udptable->hash[hash];
struct udp_hslot *hslot = udp_hashslot(udptable, sock_net(sk),
sk->sk_hash);

spin_lock_bh(&hslot->lock);
if (sk_nulls_del_node_init_rcu(sk)) {
Expand Down Expand Up @@ -1169,7 +1173,7 @@ static int __udp4_lib_mcast_deliver(struct net *net, struct sk_buff *skb,
struct udp_table *udptable)
{
struct sock *sk;
struct udp_hslot *hslot = &udptable->hash[udp_hashfn(net, ntohs(uh->dest))];
struct udp_hslot *hslot = udp_hashslot(udptable, net, ntohs(uh->dest));
int dif;

spin_lock(&hslot->lock);
Expand Down Expand Up @@ -1609,9 +1613,14 @@ static struct sock *udp_get_first(struct seq_file *seq, int start)
struct udp_iter_state *state = seq->private;
struct net *net = seq_file_net(seq);

for (state->bucket = start; state->bucket < UDP_HTABLE_SIZE; ++state->bucket) {
for (state->bucket = start; state->bucket <= state->udp_table->mask;
++state->bucket) {
struct hlist_nulls_node *node;
struct udp_hslot *hslot = &state->udp_table->hash[state->bucket];

if (hlist_nulls_empty(&hslot->head))
continue;

spin_lock_bh(&hslot->lock);
sk_nulls_for_each(sk, node, &hslot->head) {
if (!net_eq(sock_net(sk), net))
Expand All @@ -1636,7 +1645,7 @@ static struct sock *udp_get_next(struct seq_file *seq, struct sock *sk)
} while (sk && (!net_eq(sock_net(sk), net) || sk->sk_family != state->family));

if (!sk) {
if (state->bucket < UDP_HTABLE_SIZE)
if (state->bucket <= state->udp_table->mask)
spin_unlock_bh(&state->udp_table->hash[state->bucket].lock);
return udp_get_first(seq, state->bucket + 1);
}
Expand All @@ -1656,7 +1665,7 @@ static struct sock *udp_get_idx(struct seq_file *seq, loff_t pos)
static void *udp_seq_start(struct seq_file *seq, loff_t *pos)
{
struct udp_iter_state *state = seq->private;
state->bucket = UDP_HTABLE_SIZE;
state->bucket = MAX_UDP_PORTS;

return *pos ? udp_get_idx(seq, *pos-1) : SEQ_START_TOKEN;
}
Expand All @@ -1678,7 +1687,7 @@ static void udp_seq_stop(struct seq_file *seq, void *v)
{
struct udp_iter_state *state = seq->private;

if (state->bucket < UDP_HTABLE_SIZE)
if (state->bucket <= state->udp_table->mask)
spin_unlock_bh(&state->udp_table->hash[state->bucket].lock);
}

Expand Down Expand Up @@ -1738,7 +1747,7 @@ static void udp4_format_sock(struct sock *sp, struct seq_file *f,
__u16 destp = ntohs(inet->dport);
__u16 srcp = ntohs(inet->sport);

seq_printf(f, "%4d: %08X:%04X %08X:%04X"
seq_printf(f, "%5d: %08X:%04X %08X:%04X"
" %02X %08X:%08X %02X:%08lX %08X %5d %8d %lu %d %p %d%n",
bucket, src, srcp, dest, destp, sp->sk_state,
sk_wmem_alloc_get(sp),
Expand Down Expand Up @@ -1804,11 +1813,43 @@ void udp4_proc_exit(void)
}
#endif /* CONFIG_PROC_FS */

void __init udp_table_init(struct udp_table *table)
static __initdata unsigned long uhash_entries;
static int __init set_uhash_entries(char *str)
{
int i;
if (!str)
return 0;
uhash_entries = simple_strtoul(str, &str, 0);
if (uhash_entries && uhash_entries < UDP_HTABLE_SIZE_MIN)
uhash_entries = UDP_HTABLE_SIZE_MIN;
return 1;
}
__setup("uhash_entries=", set_uhash_entries);

for (i = 0; i < UDP_HTABLE_SIZE; i++) {
void __init udp_table_init(struct udp_table *table, const char *name)
{
unsigned int i;

if (!CONFIG_BASE_SMALL)
table->hash = alloc_large_system_hash(name,
sizeof(struct udp_hslot),
uhash_entries,
21, /* one slot per 2 MB */
0,
&table->log,
&table->mask,
64 * 1024);
/*
* Make sure hash table has the minimum size
*/
if (CONFIG_BASE_SMALL || table->mask < UDP_HTABLE_SIZE_MIN - 1) {
table->hash = kmalloc(UDP_HTABLE_SIZE_MIN *
sizeof(struct udp_hslot), GFP_KERNEL);
if (!table->hash)
panic(name);
table->log = ilog2(UDP_HTABLE_SIZE_MIN);
table->mask = UDP_HTABLE_SIZE_MIN - 1;
}
for (i = 0; i <= table->mask; i++) {
INIT_HLIST_NULLS_HEAD(&table->hash[i].head, i);
spin_lock_init(&table->hash[i].lock);
}
Expand All @@ -1818,7 +1859,7 @@ void __init udp_init(void)
{
unsigned long nr_pages, limit;

udp_table_init(&udp_table);
udp_table_init(&udp_table, "UDP");
/* Set the pressure threshold up by the same strategy of TCP. It is a
* fraction of global memory that is up to 1/2 at 256 MB, decreasing
* toward zero with the amount of memory, with a floor of 128 pages.
Expand Down
4 changes: 2 additions & 2 deletions net/ipv4/udplite.c
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Original file line number Diff line number Diff line change
Expand Up @@ -12,7 +12,7 @@
*/
#include "udp_impl.h"

struct udp_table udplite_table;
struct udp_table udplite_table __read_mostly;
EXPORT_SYMBOL(udplite_table);

static int udplite_rcv(struct sk_buff *skb)
Expand Down Expand Up @@ -110,7 +110,7 @@ static inline int udplite4_proc_init(void)

void __init udplite4_register(void)
{
udp_table_init(&udplite_table);
udp_table_init(&udplite_table, "UDP-Lite");
if (proto_register(&udplite_prot, 1))
goto out_register_err;

Expand Down
6 changes: 3 additions & 3 deletions net/ipv6/udp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -132,7 +132,7 @@ static struct sock *__udp6_lib_lookup(struct net *net,
struct sock *sk, *result;
struct hlist_nulls_node *node;
unsigned short hnum = ntohs(dport);
unsigned int hash = udp_hashfn(net, hnum);
unsigned int hash = udp_hashfn(net, hnum, udptable->mask);
struct udp_hslot *hslot = &udptable->hash[hash];
int score, badness;

Expand Down Expand Up @@ -452,7 +452,7 @@ static int __udp6_lib_mcast_deliver(struct net *net, struct sk_buff *skb,
{
struct sock *sk, *sk2;
const struct udphdr *uh = udp_hdr(skb);
struct udp_hslot *hslot = &udptable->hash[udp_hashfn(net, ntohs(uh->dest))];
struct udp_hslot *hslot = udp_hashslot(udptable, net, ntohs(uh->dest));
int dif;

spin_lock(&hslot->lock);
Expand Down Expand Up @@ -1197,7 +1197,7 @@ static void udp6_sock_seq_show(struct seq_file *seq, struct sock *sp, int bucket
destp = ntohs(inet->dport);
srcp = ntohs(inet->sport);
seq_printf(seq,
"%4d: %08X%08X%08X%08X:%04X %08X%08X%08X%08X:%04X "
"%5d: %08X%08X%08X%08X:%04X %08X%08X%08X%08X:%04X "
"%02X %08X:%08X %02X:%08lX %08X %5d %8d %lu %d %p %d\n",
bucket,
src->s6_addr32[0], src->s6_addr32[1],
Expand Down

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