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| author | David S. Miller <davem@davemloft.net> | 2011-03-04 21:24:47 -0800 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2011-03-04 21:24:47 -0800 |
| commit | 44713b67db10c774f14280c129b0d5fd13c70cf2 (patch) | |
| tree | 2a5fac5524dbac7b30be6409751983b597a71766 | |
| parent | 65e8354ec13a45414045084166cb340c0d7ffe8a (diff) | |
| download | linux-44713b67db10c774f14280c129b0d5fd13c70cf2.tar.bz2 | |
ipv4: Optimize flow initialization in output route lookup.
We burn a lot of useless cycles, cpu store buffer traffic, and
memory operations memset()'ing the on-stack flow used to perform
output route lookups in __ip_route_output_key().
Only the first half of the flow object members even matter for
output route lookups in this context, specifically:
FIB rules matching cares about:
dst, src, tos, iif, oif, mark
FIB trie lookup cares about:
dst
FIB semantic match cares about:
tos, scope, oif
Therefore only initialize these specific members and elide the
memset entirely.
On Niagara2 this kills about ~300 cycles from the output route
lookup path.
Likely, we can take things further, since all callers of output
route lookups essentially throw away the on-stack flow they use.
So they don't care if we use it as a scratch-pad to compute the
final flow key.
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
| -rw-r--r-- | net/ipv4/route.c | 18 |
1 files changed, 10 insertions, 8 deletions
diff --git a/net/ipv4/route.c b/net/ipv4/route.c index 432eee645648..6c8740362ef9 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -2431,14 +2431,7 @@ static struct rtable *ip_route_output_slow(struct net *net, const struct flowi *oldflp) { u32 tos = RT_FL_TOS(oldflp); - struct flowi fl = { .fl4_dst = oldflp->fl4_dst, - .fl4_src = oldflp->fl4_src, - .fl4_tos = tos & IPTOS_RT_MASK, - .fl4_scope = ((tos & RTO_ONLINK) ? - RT_SCOPE_LINK : RT_SCOPE_UNIVERSE), - .mark = oldflp->mark, - .iif = net->loopback_dev->ifindex, - .oif = oldflp->oif }; + struct flowi fl; struct fib_result res; unsigned int flags = 0; struct net_device *dev_out = NULL; @@ -2449,6 +2442,15 @@ static struct rtable *ip_route_output_slow(struct net *net, res.r = NULL; #endif + fl.oif = oldflp->oif; + fl.iif = net->loopback_dev->ifindex; + fl.mark = oldflp->mark; + fl.fl4_dst = oldflp->fl4_dst; + fl.fl4_src = oldflp->fl4_src; + fl.fl4_tos = tos & IPTOS_RT_MASK; + fl.fl4_scope = ((tos & RTO_ONLINK) ? + RT_SCOPE_LINK : RT_SCOPE_UNIVERSE); + rcu_read_lock(); if (oldflp->fl4_src) { rth = ERR_PTR(-EINVAL); |