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author | Eric Dumazet <dada1@cosmosbay.com> | 2008-01-20 22:12:16 +0200 |
---|---|---|
committer | Adrian Bunk <bunk@kernel.org> | 2008-01-20 22:12:16 +0200 |
commit | d2c758a5fa26777d955fc2bade9c338d1aed5117 (patch) | |
tree | ffc45d1ac93ff8caa4235c140fbcc2b08fe2d41e | |
parent | 9160766b83a51267e3cd2987ed3c2690e3d059f9 (diff) | |
download | lwn-d2c758a5fa26777d955fc2bade9c338d1aed5117.tar.gz lwn-d2c758a5fa26777d955fc2bade9c338d1aed5117.zip |
[IPV4] ROUTE: ip_rt_dump() is unecessary slow
[ Upstream commit: d8c9283089287341c85a0a69de32c2287a990e71 ]
I noticed "ip route list cache x.y.z.t" can be *very* slow.
While strace-ing -T it I also noticed that first part of route cache
is fetched quite fast :
recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000},
+msg_iov(1)=[{"p\0\0\0\30\0\2\0\254i\202
GXm\0\0\2 \0\376\0\0\2\0\2\0"..., 16384}], msg_controllen=0, msg_flags=0}, 0) =
+3772 <0.000047>
recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000},
+msg_iov(1)=[{"\234\0\0\0\30\0\2\0\254i\
202GXm\0\0\2 \0\376\0\0\1\0\2"..., 16384}], msg_controllen=0, msg_flags=0}, 0)
+= 3736 <0.000042>
recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000},
+msg_iov(1)=[{"\204\0\0\0\30\0\2\0\254i\
202GXm\0\0\2 \0\376\0\0\1\0\2"..., 16384}], msg_controllen=0, msg_flags=0}, 0)
+= 3740 <0.000055>
recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000},
+msg_iov(1)=[{"\234\0\0\0\30\0\2\0\254i\
202GXm\0\0\2 \0\376\0\0\1\0\2"..., 16384}], msg_controllen=0, msg_flags=0}, 0)
+= 3712 <0.000043>
recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000},
+msg_iov(1)=[{"\204\0\0\0\30\0\2\0\254i\
202GXm\0\0\2 \0\376\0\0\1\0\2"..., 16384}], msg_controllen=0, msg_flags=0}, 0)
+= 3732 <0.000053>
recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000},
+msg_iov(1)=[{"p\0\0\0\30\0\2\0\254i\202
GXm\0\0\2 \0\376\0\0\2\0\2\0"..., 16384}], msg_controllen=0, msg_flags=0}, 0) =
+3708 <0.000052>
recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000},
+msg_iov(1)=[{"p\0\0\0\30\0\2\0\254i\202
GXm\0\0\2 \0\376\0\0\2\0\2\0"..., 16384}], msg_controllen=0, msg_flags=0}, 0) =
+3680 <0.000041>
while the part at the end of the table is more expensive:
recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000},
+msg_iov(1)=[{"\204\0\0\0\30\0\2\0\254i\202GXm\0\0\2 \0\376\0\0\1\0\2"...,
+16384}], msg_controllen=0, msg_flags=0}, 0) = 3656 <0.003857>
recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000},
+msg_iov(1)=[{"\204\0\0\0\30\0\2\0\254i\202GXm\0\0\2 \0\376\0\0\1\0\2"...,
+16384}], msg_controllen=0, msg_flags=0}, 0) = 3772 <0.003891>
recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000},
+msg_iov(1)=[{"p\0\0\0\30\0\2\0\254i\202GXm\0\0\2 \0\376\0\0\2\0\2\0"...,
+16384}], msg_controllen=0, msg_flags=0}, 0) = 3712 <0.003765>
recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000},
+msg_iov(1)=[{"p\0\0\0\30\0\2\0\254i\202GXm\0\0\2 \0\376\0\0\2\0\2\0"...,
+16384}], msg_controllen=0, msg_flags=0}, 0) = 3700 <0.003879>
recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000},
+msg_iov(1)=[{"p\0\0\0\30\0\2\0\254i\202GXm\0\0\2 \0\376\0\0\2\0\2\0"...,
+16384}], msg_controllen=0, msg_flags=0}, 0) = 3676 <0.003797>
recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000},
+msg_iov(1)=[{"p\0\0\0\30\0\2\0\254i\202GXm\0\0\2 \0\376\0\0\2\0\2\0"...,
+16384}], msg_controllen=0, msg_flags=0}, 0) = 3724 <0.003856>
recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000},
+msg_iov(1)=[{"\234\0\0\0\30\0\2\0\254i\202GXm\0\0\2 \0\376\0\0\1\0\2"...,
+16384}], msg_controllen=0, msg_flags=0}, 0) = 3736 <0.003848>
The following patch corrects this performance/latency problem,
removing quadratic behavior.
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Adrian Bunk <bunk@kernel.org>
-rw-r--r-- | net/ipv4/route.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/net/ipv4/route.c b/net/ipv4/route.c index c83066cc342a..ba7e8ebd7453 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -2821,11 +2821,10 @@ int ip_rt_dump(struct sk_buff *skb, struct netlink_callback *cb) int idx, s_idx; s_h = cb->args[0]; + if (s_h < 0) + s_h = 0; s_idx = idx = cb->args[1]; - for (h = 0; h <= rt_hash_mask; h++) { - if (h < s_h) continue; - if (h > s_h) - s_idx = 0; + for (h = s_h; h <= rt_hash_mask; h++) { rcu_read_lock_bh(); for (rt = rcu_dereference(rt_hash_table[h].chain), idx = 0; rt; rt = rcu_dereference(rt->u.rt_next), idx++) { @@ -2842,6 +2841,7 @@ int ip_rt_dump(struct sk_buff *skb, struct netlink_callback *cb) dst_release(xchg(&skb->dst, NULL)); } rcu_read_unlock_bh(); + s_idx = 0; } done: |