| Message ID | 20180109144028.30133-5-idosch@mellanox.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
| Series | ipv6: Add support for non-equal-cost multipath | expand |
On 1/9/18 7:40 AM, Ido Schimmel wrote: > The use of hash-threshold instead of modulo-N makes it trivial to add > support for non-equal-cost multipath. > > Instead of dividing the multipath hash function's output space equally > between the nexthops, each nexthop is assigned a region size which is > proportional to its weight. > > Signed-off-by: Ido Schimmel <idosch@mellanox.com> > --- > include/net/ip6_fib.h | 1 + > net/ipv6/route.c | 11 +++++++---- > 2 files changed, 8 insertions(+), 4 deletions(-) > > diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h > index 97cd05d87780..34ec321d6a03 100644 > --- a/include/net/ip6_fib.h > +++ b/include/net/ip6_fib.h > @@ -171,6 +171,7 @@ struct rt6_info { > u32 rt6i_metric; > u32 rt6i_pmtu; > /* more non-fragment space at head required */ > + int rt6i_nh_weight; > unsigned short rt6i_nfheader_len; > u8 rt6i_protocol; > u8 exception_bucket_flushed:1, Since dst is cacheline aligned there is a hole after rt6i_nh_flags. In patch 1 you put rt6i_nh_upper_bound in that hole. Putting the weight there too keeps those variables together as well as using the open space.
Hi David, On Tue, Jan 09, 2018 at 08:48:37PM -0700, David Ahern wrote: > On 1/9/18 7:40 AM, Ido Schimmel wrote: > > The use of hash-threshold instead of modulo-N makes it trivial to add > > support for non-equal-cost multipath. > > > > Instead of dividing the multipath hash function's output space equally > > between the nexthops, each nexthop is assigned a region size which is > > proportional to its weight. > > > > Signed-off-by: Ido Schimmel <idosch@mellanox.com> > > --- > > include/net/ip6_fib.h | 1 + > > net/ipv6/route.c | 11 +++++++---- > > 2 files changed, 8 insertions(+), 4 deletions(-) > > > > diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h > > index 97cd05d87780..34ec321d6a03 100644 > > --- a/include/net/ip6_fib.h > > +++ b/include/net/ip6_fib.h > > @@ -171,6 +171,7 @@ struct rt6_info { > > u32 rt6i_metric; > > u32 rt6i_pmtu; > > /* more non-fragment space at head required */ > > + int rt6i_nh_weight; > > unsigned short rt6i_nfheader_len; > > u8 rt6i_protocol; > > u8 exception_bucket_flushed:1, > > Since dst is cacheline aligned there is a hole after rt6i_nh_flags. In > patch 1 you put rt6i_nh_upper_bound in that hole. Putting the weight > there too keeps those variables together as well as using the open space. Before patch 1 there's a hole of 4 bytes after rt6i_nh_flags which I use for rt6i_nh_upper_bound. If I put rt6i_nh_weight there as well, then I create a 60 bytes hole because the dst needs to be cached aligned. Since rt6i_nh_weight isn't used in fast-path, I just put it at the end.
On 1/10/18 4:47 AM, Ido Schimmel wrote: > Hi David, > > On Tue, Jan 09, 2018 at 08:48:37PM -0700, David Ahern wrote: >> On 1/9/18 7:40 AM, Ido Schimmel wrote: >>> The use of hash-threshold instead of modulo-N makes it trivial to add >>> support for non-equal-cost multipath. >>> >>> Instead of dividing the multipath hash function's output space equally >>> between the nexthops, each nexthop is assigned a region size which is >>> proportional to its weight. >>> >>> Signed-off-by: Ido Schimmel <idosch@mellanox.com> >>> --- >>> include/net/ip6_fib.h | 1 + >>> net/ipv6/route.c | 11 +++++++---- >>> 2 files changed, 8 insertions(+), 4 deletions(-) >>> >>> diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h >>> index 97cd05d87780..34ec321d6a03 100644 >>> --- a/include/net/ip6_fib.h >>> +++ b/include/net/ip6_fib.h >>> @@ -171,6 +171,7 @@ struct rt6_info { >>> u32 rt6i_metric; >>> u32 rt6i_pmtu; >>> /* more non-fragment space at head required */ >>> + int rt6i_nh_weight; >>> unsigned short rt6i_nfheader_len; >>> u8 rt6i_protocol; >>> u8 exception_bucket_flushed:1, >> >> Since dst is cacheline aligned there is a hole after rt6i_nh_flags. In >> patch 1 you put rt6i_nh_upper_bound in that hole. Putting the weight >> there too keeps those variables together as well as using the open space. > > Before patch 1 there's a hole of 4 bytes after rt6i_nh_flags which I use > for rt6i_nh_upper_bound. If I put rt6i_nh_weight there as well, then I > create a 60 bytes hole because the dst needs to be cached aligned. > > Since rt6i_nh_weight isn't used in fast-path, I just put it at the end. > Apparently, I was on a 4.14 branch when I ran pahole to dump the layout of rt6_info. The patch looks good to me. Acked-by: David Ahern <dsahern@gmail.com>
diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h index 97cd05d87780..34ec321d6a03 100644 --- a/include/net/ip6_fib.h +++ b/include/net/ip6_fib.h @@ -171,6 +171,7 @@ struct rt6_info { u32 rt6i_metric; u32 rt6i_pmtu; /* more non-fragment space at head required */ + int rt6i_nh_weight; unsigned short rt6i_nfheader_len; u8 rt6i_protocol; u8 exception_bucket_flushed:1, diff --git a/net/ipv6/route.c b/net/ipv6/route.c index 7837b8c754a3..1076ae0ea9d5 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -2594,6 +2594,7 @@ static struct rt6_info *ip6_route_info_create(struct fib6_config *cfg, #endif rt->rt6i_metric = cfg->fc_metric; + rt->rt6i_nh_weight = 1; /* We cannot add true routes via loopback here, they would result in kernel looping; promote them to reject routes @@ -3507,11 +3508,11 @@ static int rt6_multipath_total_weight(const struct rt6_info *rt) int total = 0; if (!rt6_is_dead(rt)) - total++; + total += rt->rt6i_nh_weight; list_for_each_entry(iter, &rt->rt6i_siblings, rt6i_siblings) { if (!rt6_is_dead(iter)) - total++; + total += iter->rt6i_nh_weight; } return total; @@ -3522,7 +3523,7 @@ static void rt6_upper_bound_set(struct rt6_info *rt, int *weight, int total) int upper_bound = -1; if (!rt6_is_dead(rt)) { - (*weight)++; + *weight += rt->rt6i_nh_weight; upper_bound = DIV_ROUND_CLOSEST_ULL((u64) (*weight) << 31, total) - 1; } @@ -4024,6 +4025,8 @@ static int ip6_route_multipath_add(struct fib6_config *cfg, goto cleanup; } + rt->rt6i_nh_weight = rtnh->rtnh_hops + 1; + err = ip6_route_info_append(&rt6_nh_list, rt, &r_cfg); if (err) { dst_release_immediate(&rt->dst); @@ -4246,7 +4249,7 @@ static int rt6_add_nexthop(struct sk_buff *skb, struct rt6_info *rt) if (!rtnh) goto nla_put_failure; - rtnh->rtnh_hops = 0; + rtnh->rtnh_hops = rt->rt6i_nh_weight - 1; rtnh->rtnh_ifindex = rt->dst.dev ? rt->dst.dev->ifindex : 0; if (rt6_nexthop_info(skb, rt, &flags, true) < 0)
The use of hash-threshold instead of modulo-N makes it trivial to add support for non-equal-cost multipath. Instead of dividing the multipath hash function's output space equally between the nexthops, each nexthop is assigned a region size which is proportional to its weight. Signed-off-by: Ido Schimmel <idosch@mellanox.com> --- include/net/ip6_fib.h | 1 + net/ipv6/route.c | 11 +++++++---- 2 files changed, 8 insertions(+), 4 deletions(-)