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authorHerbert Xu <herbert@gondor.apana.org.au>2007-06-10 17:33:08 -0700
committerDavid S. Miller <davem@sunset.davemloft.net>2007-07-10 22:06:20 -0700
commita7ab4b501f9b8a9dc4d5cee542db67b6ccd1088b (patch)
treef84fa3241fddf8ed8320ace50fed11170ce7860b
parent[NET_SCHED]: Cleanup readability of qdisc restart (diff)
downloadlinux-dev-a7ab4b501f9b8a9dc4d5cee542db67b6ccd1088b.tar.xz
linux-dev-a7ab4b501f9b8a9dc4d5cee542db67b6ccd1088b.zip
[TCPv4]: Improve BH latency in /proc/net/tcp
Currently the code for /proc/net/tcp disable BH while iterating over the entire established hash table. Even though we call cond_resched_softirq for each entry, we still won't process softirq's as regularly as we would otherwise do which results in poor performance when the system is loaded near capacity. This anomaly comes from the 2.4 code where this was all in a single function and the local_bh_disable might have made sense as a small optimisation. The cost of each local_bh_disable is so small when compared against the increased latency in keeping it disabled over a large but mostly empty TCP established hash table that we should just move it to the individual read_lock/read_unlock calls as we do in inet_diag. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/ipv4/tcp_ipv4.c19
1 files changed, 5 insertions, 14 deletions
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 354721d67f69..3f5f7423b95c 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2045,10 +2045,7 @@ static void *established_get_first(struct seq_file *seq)
struct hlist_node *node;
struct inet_timewait_sock *tw;
- /* We can reschedule _before_ having picked the target: */
- cond_resched_softirq();
-
- read_lock(&tcp_hashinfo.ehash[st->bucket].lock);
+ read_lock_bh(&tcp_hashinfo.ehash[st->bucket].lock);
sk_for_each(sk, node, &tcp_hashinfo.ehash[st->bucket].chain) {
if (sk->sk_family != st->family) {
continue;
@@ -2065,7 +2062,7 @@ static void *established_get_first(struct seq_file *seq)
rc = tw;
goto out;
}
- read_unlock(&tcp_hashinfo.ehash[st->bucket].lock);
+ read_unlock_bh(&tcp_hashinfo.ehash[st->bucket].lock);
st->state = TCP_SEQ_STATE_ESTABLISHED;
}
out:
@@ -2092,14 +2089,11 @@ get_tw:
cur = tw;
goto out;
}
- read_unlock(&tcp_hashinfo.ehash[st->bucket].lock);
+ read_unlock_bh(&tcp_hashinfo.ehash[st->bucket].lock);
st->state = TCP_SEQ_STATE_ESTABLISHED;
- /* We can reschedule between buckets: */
- cond_resched_softirq();
-
if (++st->bucket < tcp_hashinfo.ehash_size) {
- read_lock(&tcp_hashinfo.ehash[st->bucket].lock);
+ read_lock_bh(&tcp_hashinfo.ehash[st->bucket].lock);
sk = sk_head(&tcp_hashinfo.ehash[st->bucket].chain);
} else {
cur = NULL;
@@ -2144,7 +2138,6 @@ static void *tcp_get_idx(struct seq_file *seq, loff_t pos)
if (!rc) {
inet_listen_unlock(&tcp_hashinfo);
- local_bh_disable();
st->state = TCP_SEQ_STATE_ESTABLISHED;
rc = established_get_idx(seq, pos);
}
@@ -2177,7 +2170,6 @@ static void *tcp_seq_next(struct seq_file *seq, void *v, loff_t *pos)
rc = listening_get_next(seq, v);
if (!rc) {
inet_listen_unlock(&tcp_hashinfo);
- local_bh_disable();
st->state = TCP_SEQ_STATE_ESTABLISHED;
rc = established_get_first(seq);
}
@@ -2209,8 +2201,7 @@ static void tcp_seq_stop(struct seq_file *seq, void *v)
case TCP_SEQ_STATE_TIME_WAIT:
case TCP_SEQ_STATE_ESTABLISHED:
if (v)
- read_unlock(&tcp_hashinfo.ehash[st->bucket].lock);
- local_bh_enable();
+ read_unlock_bh(&tcp_hashinfo.ehash[st->bucket].lock);
break;
}
}