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Commit 8d3f099a authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
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[IPV4] FIB_HASH : Avoid unecessary loop in fn_hash_dump_zone() 



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
d8c92830 ("[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: default avatarEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 49d85c50

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;