[IPV4] FIB_HASH : Avoid unecessary loop in fn_hash_dump_zone() (8d3f099a) · Commits · 戴 / test

I noticed "ip route list" was slower than "cat /proc/net/route" on a machine with a full Internet routing table (214392 entries : Special thanks to Robert ;) ) This is similar to problem reported in commit ("[IPV4] ROUTE: ip_rt_dump() is unecessary slow") Fix is to avoid scanning the begining of fz_hash table, but directly seek to the right offset. Before patch : time ip route >/tmp/ROUTE real 0m1.285s user 0m0.712s sys 0m0.436s After patch # time ip route >/tmp/ROUTE real 0m0.835s user 0m0.692s sys 0m0.124s Signed-off-by:

Eric Dumazet <dada1@cosmosbay.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/ipv4/fib_hash.c

+9 −11

Original line number	Diff line number	Diff line
		@@ -721,19 +721,18 @@ fn_hash_dump_zone(struct sk_buff skb, struct netlink_callback cb,
		{
		int h, s_h;

		if (fz->fz_hash == NULL)
		return skb->len;
		s_h = cb->args[3];
		for (h=0; h < fz->fz_divisor; h++) {
		if (h < s_h) continue;
		if (h > s_h)
		memset(&cb->args[4], 0,
		sizeof(cb->args) - 4*sizeof(cb->args[0]));
		if (fz->fz_hash == NULL \|\|
		hlist_empty(&fz->fz_hash[h]))
		for (h = s_h; h < fz->fz_divisor; h++) {
		if (hlist_empty(&fz->fz_hash[h]))
		continue;
		if (fn_hash_dump_bucket(skb, cb, tb, fz, &fz->fz_hash[h]) < 0) {
		cb->args[3] = h;
		return -1;
		}
		memset(&cb->args[4], 0,
		sizeof(cb->args) - 4*sizeof(cb->args[0]));
		}
		cb->args[3] = h;
		return skb->len;
		@@ -749,14 +748,13 @@ static int fn_hash_dump(struct fib_table tb, struct sk_buff skb, struct netlin
		read_lock(&fib_hash_lock);
		for (fz = table->fn_zone_list, m=0; fz; fz = fz->fz_next, m++) {
		if (m < s_m) continue;
		if (m > s_m)
		memset(&cb->args[3], 0,
		sizeof(cb->args) - 3*sizeof(cb->args[0]));
		if (fn_hash_dump_zone(skb, cb, tb, fz) < 0) {
		cb->args[2] = m;
		read_unlock(&fib_hash_lock);
		return -1;
		}
		memset(&cb->args[3], 0,
		sizeof(cb->args) - 3*sizeof(cb->args[0]));
		}
		read_unlock(&fib_hash_lock);
		cb->args[2] = m;

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