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authorEric Dumazet <dada1@cosmosbay.com>2009-01-26 21:35:35 -0800
committerDavid S. Miller <davem@davemloft.net>2009-01-26 21:35:35 -0800
commit98322f22eca889478045cf896b572250d03dc45f (patch)
tree22a06e97ece02db900f7d4f496639582b828a4ee /net
parent8527bec548e01a29c6d1928d20d6d3be71861482 (diff)
downloadlinux-98322f22eca889478045cf896b572250d03dc45f.tar.bz2
udp: optimize bind(0) if many ports are in use
commit 9088c5609584684149f3fb5b065aa7f18dcb03ff (udp: Improve port randomization) introduced a regression for UDP bind() syscall to null port (getting a random port) in case lot of ports are already in use. This is because we do about 28000 scans of very long chains (220 sockets per chain), with many spin_lock_bh()/spin_unlock_bh() calls. Fix this using a bitmap (64 bytes for current value of UDP_HTABLE_SIZE) so that we scan chains at most once. Instead of 250 ms per bind() call, we get after patch a time of 2.9 ms Based on a report from Vitaly Mayatskikh Reported-by: Vitaly Mayatskikh <v.mayatskih@gmail.com> Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Tested-by: Vitaly Mayatskikh <v.mayatskih@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/udp.c55
1 files changed, 39 insertions, 16 deletions
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index cf5ab0581eba..b7faffe5c029 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -120,8 +120,11 @@ EXPORT_SYMBOL(sysctl_udp_wmem_min);
atomic_t udp_memory_allocated;
EXPORT_SYMBOL(udp_memory_allocated);
+#define PORTS_PER_CHAIN (65536 / UDP_HTABLE_SIZE)
+
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))
@@ -132,12 +135,17 @@ static int udp_lib_lport_inuse(struct net *net, __u16 num,
sk_nulls_for_each(sk2, node, &hslot->head)
if (net_eq(sock_net(sk2), net) &&
sk2 != sk &&
- sk2->sk_hash == num &&
+ (bitmap || sk2->sk_hash == num) &&
(!sk2->sk_reuse || !sk->sk_reuse) &&
(!sk2->sk_bound_dev_if || !sk->sk_bound_dev_if
|| sk2->sk_bound_dev_if == sk->sk_bound_dev_if) &&
- (*saddr_comp)(sk, sk2))
- return 1;
+ (*saddr_comp)(sk, sk2)) {
+ if (bitmap)
+ __set_bit(sk2->sk_hash / UDP_HTABLE_SIZE,
+ bitmap);
+ else
+ return 1;
+ }
return 0;
}
@@ -160,32 +168,47 @@ int udp_lib_get_port(struct sock *sk, unsigned short snum,
if (!snum) {
int low, high, remaining;
unsigned rand;
- unsigned short first;
+ unsigned short first, last;
+ DECLARE_BITMAP(bitmap, PORTS_PER_CHAIN);
inet_get_local_port_range(&low, &high);
remaining = (high - low) + 1;
rand = net_random();
- snum = first = rand % remaining + low;
- rand |= 1;
- for (;;) {
- hslot = &udptable->hash[udp_hashfn(net, snum)];
+ first = (((u64)rand * remaining) >> 32) + low;
+ /*
+ * 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)];
+ bitmap_zero(bitmap, PORTS_PER_CHAIN);
spin_lock_bh(&hslot->lock);
- if (!udp_lib_lport_inuse(net, snum, hslot, sk, saddr_comp))
- break;
- spin_unlock_bh(&hslot->lock);
+ udp_lib_lport_inuse(net, snum, hslot, bitmap, sk,
+ saddr_comp);
+
+ snum = first;
+ /*
+ * Iterate on all possible values of snum for this hash.
+ * Using steps of an odd multiple of UDP_HTABLE_SIZE
+ * give us randomization and full range coverage.
+ */
do {
- snum = snum + rand;
- } while (snum < low || snum > high);
- if (snum == first)
- goto fail;
+ if (low <= snum && snum <= high &&
+ !test_bit(snum / UDP_HTABLE_SIZE, bitmap))
+ goto found;
+ snum += rand;
+ } while (snum != first);
+ spin_unlock_bh(&hslot->lock);
}
+ goto fail;
} else {
hslot = &udptable->hash[udp_hashfn(net, snum)];
spin_lock_bh(&hslot->lock);
- if (udp_lib_lport_inuse(net, snum, hslot, sk, saddr_comp))
+ if (udp_lib_lport_inuse(net, snum, hslot, NULL, sk, saddr_comp))
goto fail_unlock;
}
+found:
inet_sk(sk)->num = snum;
sk->sk_hash = snum;
if (sk_unhashed(sk)) {