[PATCH net-next] net: copy routing table more efficiently in rt_dst_clone

[PATCH net-next] net: copy routing table more efficiently in rt_dst_clone

[Oliver Crumrine]

Instead of copying field-by-field, copy the entire struct at once. This
should lead to a performance improvment in rt_dst_clone.

Signed-off-by: Oliver Crumrine <ozlinuxc@gmail.com>
---
 net/ipv4/route.c | 16 +---------------
 1 file changed, 1 insertion(+), 15 deletions(-)

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 16615d107cf0..ebb17c3a0dec 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1664,22 +1664,8 @@ struct rtable *rt_dst_clone(struct net_device *dev, struct rtable *rt)
 			   rt->dst.flags);
 
 	if (new_rt) {
+		*new_rt = *rt;
 		new_rt->rt_genid = rt_genid_ipv4(dev_net(dev));
-		new_rt->rt_flags = rt->rt_flags;
-		new_rt->rt_type = rt->rt_type;
-		new_rt->rt_is_input = rt->rt_is_input;
-		new_rt->rt_iif = rt->rt_iif;
-		new_rt->rt_pmtu = rt->rt_pmtu;
-		new_rt->rt_mtu_locked = rt->rt_mtu_locked;
-		new_rt->rt_gw_family = rt->rt_gw_family;
-		if (rt->rt_gw_family == AF_INET)
-			new_rt->rt_gw4 = rt->rt_gw4;
-		else if (rt->rt_gw_family == AF_INET6)
-			new_rt->rt_gw6 = rt->rt_gw6;
-
-		new_rt->dst.input = rt->dst.input;
-		new_rt->dst.output = rt->dst.output;
-		new_rt->dst.error = rt->dst.error;
 		new_rt->dst.lastuse = jiffies;
 		new_rt->dst.lwtstate = lwtstate_get(rt->dst.lwtstate);
 	}
-- 
2.43.0

Re: [PATCH net-next] net: copy routing table more efficiently in rt_dst_clone

[David Ahern]

On 2/18/24 6:35 AM, Oliver Crumrine wrote:
> diff --git a/net/ipv4/route.c b/net/ipv4/route.c
> index 16615d107cf0..ebb17c3a0dec 100644
> --- a/net/ipv4/route.c
> +++ b/net/ipv4/route.c
> @@ -1664,22 +1664,8 @@ struct rtable *rt_dst_clone(struct net_device *dev, struct rtable *rt)
>  			   rt->dst.flags);
>  
>  	if (new_rt) {
> +		*new_rt = *rt;

rtable is a container of dst_entry, so this is copying those fields as well.

pw-bot: reject

Re: [PATCH net-next] net: copy routing table more efficiently in rt_dst_clone

[Oliver Crumrine]

On Tue, Feb 20, 2024 at 07:44:24PM -0700, David Ahern wrote:
Hi David,

You are correct that rtable is a container of dst_entry, and the
previous code copied not only the fields of rtable but also the fields
of dst_entry. However, the *new_rt = *rt line not only copies the fields
of rtable, but also the fields of dst_entry. 

I have demonstrated this by generating a random number and putting it in
the "expired" field of the dst_entry that is part of rt, and the printing
the random number that was generated. After the copy, I printed the
expired field of the dst_entry that is part of new_rt and the numbers
matched. This proves that not only the fields that were part of rtable
were copied but also the fields of dst_entry.

Thanks,
Oliver
> On 2/18/24 6:35 AM, Oliver Crumrine wrote:
> > diff --git a/net/ipv4/route.c b/net/ipv4/route.c
> > index 16615d107cf0..ebb17c3a0dec 100644
> > --- a/net/ipv4/route.c
> > +++ b/net/ipv4/route.c
> > @@ -1664,22 +1664,8 @@ struct rtable *rt_dst_clone(struct net_device *dev, struct rtable *rt)
> >  			   rt->dst.flags);
> >  
> >  	if (new_rt) {
> > +		*new_rt = *rt;
> 
> rtable is a container of dst_entry, so this is copying those fields as well.
> 
> pw-bot: reject
>