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net: sched: don't release block->lock when dumping chains

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Function tc_dump_chain() obtains and releases block->lock on each iteration
of its inner loop that dumps all chains on block. Outputting chain template
info is fast operation so locking/unlocking mutex multiple times is an
overhead when lock is highly contested. Modify tc_dump_chain() to only
obtain block->lock once and dump all chains without releasing it.

Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Suggested-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Vlad Buslov 2019-02-25 17:45:44 +02:00 committed by David S. Miller
parent 6676d5e416
commit ace4a267e8
1 changed files with 7 additions and 9 deletions
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16
net/sched/cls_api.c
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@ -2912,12 +2912,12 @@ static int tc_ctl_chain(struct sk_buff *skb, struct nlmsghdr *n,
/* called with RTNL */
static int tc_dump_chain(struct sk_buff *skb, struct netlink_callback *cb)
{
struct tcf_chain *chain, *chain_prev;
struct net *net = sock_net(skb->sk);
struct nlattr *tca[TCA_MAX + 1];
struct Qdisc *q = NULL;
struct tcf_block *block;
struct tcmsg *tcm = nlmsg_data(cb->nlh);
struct tcf_chain *chain;
long index_start;
long index;
u32 parent;
@ -2980,11 +2980,8 @@ static int tc_dump_chain(struct sk_buff *skb, struct netlink_callback *cb)
index_start = cb->args[0];
index = 0;
for (chain = __tcf_get_next_chain(block, NULL);
chain;
chain_prev = chain,
chain = __tcf_get_next_chain(block, chain),
tcf_chain_put(chain_prev)) {
mutex_lock(&block->lock);
list_for_each_entry(chain, &block->chain_list, list) {
if ((tca[TCA_CHAIN] &&
nla_get_u32(tca[TCA_CHAIN]) != chain->index))
continue;
@ -2992,17 +2989,18 @@ static int tc_dump_chain(struct sk_buff *skb, struct netlink_callback *cb)
index++;
continue;
}
if (tcf_chain_held_by_acts_only(chain))
continue;
err = tc_chain_fill_node(chain->tmplt_ops, chain->tmplt_priv,
chain->index, net, skb, block,
NETLINK_CB(cb->skb).portid,
cb->nlh->nlmsg_seq, NLM_F_MULTI,
RTM_NEWCHAIN);
if (err <= 0) {
tcf_chain_put(chain);
if (err <= 0)
break;
}
index++;
}
mutex_unlock(&block->lock);
if (tcm->tcm_ifindex == TCM_IFINDEX_MAGIC_BLOCK)
tcf_block_refcnt_put(block, true);