Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20230112012532.311021-1-jmaxwell37@gmail.com> <20230112214140.b490f5e77e46d9cdab53d2b2@uniroma2.it>
In-Reply-To: <20230112214140.b490f5e77e46d9cdab53d2b2@uniroma2.it>
From:   Jonathan Maxwell <jmaxwell37@gmail.com>
Date:   Fri, 13 Jan 2023 08:48:24 +1100
Message-ID: <CAGHK07DvW1NmfWE+6tFEpY3tkNpFYXitebJh1o8HYk_1=MdoaQ@mail.gmail.com>
Subject: Re: [net-next v2] ipv6: remove max_size check inline with ipv4
To:     Andrea Mayer <andrea.mayer@uniroma2.it>
Cc:     davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
        pabeni@redhat.com, yoshfuji@linux-ipv6.org, dsahern@kernel.org,
        martin.lau@kernel.org, joel@joelfernandes.org, paulmck@kernel.org,
        eyal.birger@gmail.com, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Hi Andrea,

On Fri, Jan 13, 2023 at 7:41 AM Andrea Mayer <andrea.mayer@uniroma2.it> wrote:
>
> Hi Jon,
>
> On Thu, 12 Jan 2023 12:25:32 +1100
> Jon Maxwell <jmaxwell37@gmail.com> wrote:
>
> > v2: Correct syntax error in net/ipv6/route.c
> >
> > In ip6_dst_gc() replace:
> >
> > if (entries > gc_thresh)
> >
> > With:
> >
> > if (entries > ops->gc_thresh)
> >
> > Sending Ipv6 packets in a loop via a raw socket triggers an issue where a
> > route is cloned by ip6_rt_cache_alloc() for each packet sent. This quickly
> > consumes the Ipv6 max_size threshold which defaults to 4096 resulting in
> > these warnings:
> >
> > [1]   99.187805] dst_alloc: 7728 callbacks suppressed
> > [2] Route cache is full: consider increasing sysctl net.ipv6.route.max_size.
> > .
> > .
> > [300] Route cache is full: consider increasing sysctl net.ipv6.route.max_size.
> >
> > When this happens the packet is dropped and sendto() gets a network is
> > unreachable error:
> >
> > # ./a.out -s
> >
> > remaining pkt 200557 errno 101
> > remaining pkt 196462 errno 101
> > .
> > .
> > remaining pkt 126821 errno 101
> >
> > Implement David Aherns suggestion to remove max_size check seeing that Ipv6
> > has a GC to manage memory usage. Ipv4 already does not check max_size.
> >
> > Here are some memory comparisons for Ipv4 vs Ipv6 with the patch:
> >
> > Test by running 5 instances of a program that sends UDP packets to a raw
> > socket 5000000 times. Compare Ipv4 and Ipv6 performance with a similar
> > program.
> >
> > Ipv4:
> >
>
> is it supposed to be Ipv6, right?
>

No, That is for Ipv4, DavidA asked me to include a comparison between Ipv4
and Ipv6.  So that is taken for a test running 5 processes that sends 5000000
packets on  an ipv4 raw socket. If you scroll down, Ipv6 memory statistics
are under "Ipv6 with patch:".

Regards

Jon

> Ciao,
> Andrea
>
> > Before test:
> >
> > # grep -e Slab -e Free /proc/meminfo
> > MemFree:        29427108 kB
> > Slab:             237612 kB
> >
> > # grep dst_cache /proc/slabinfo
> > ip6_dst_cache       1912   2528    256   32    2 : tunables    0    0    0
> > xfrm_dst_cache         0      0    320   25    2 : tunables    0    0    0
> > ip_dst_cache        2881   3990    192   42    2 : tunables    0    0    0
> >
> > During test:
> >
> > # grep -e Slab -e Free /proc/meminfo
> > MemFree:        29417608 kB
> > Slab:             247712 kB
> >
> > # grep dst_cache /proc/slabinfo
> > ip6_dst_cache       1912   2528    256   32    2 : tunables    0    0    0
> > xfrm_dst_cache         0      0    320   25    2 : tunables    0    0    0
> > ip_dst_cache       44394  44394    192   42    2 : tunables    0    0    0
> >
> > After test:
> >
> > # grep -e Slab -e Free /proc/meminfo
> > MemFree:        29422308 kB
> > Slab:             238104 kB
> >
> > # grep dst_cache /proc/slabinfo
> > ip6_dst_cache       1912   2528    256   32    2 : tunables    0    0    0
> > xfrm_dst_cache         0      0    320   25    2 : tunables    0    0    0
> > ip_dst_cache        3048   4116    192   42    2 : tunables    0    0    0
> >
> > Ipv6 with patch:
> >
> > Errno 101 errors are not observed anymore with the patch.
> >
> > Before test:
> >
> > # grep -e Slab -e Free /proc/meminfo
> > MemFree:        29422308 kB
> > Slab:             238104 kB
> >
> > # grep dst_cache /proc/slabinfo
> > ip6_dst_cache       1912   2528    256   32    2 : tunables    0    0    0
> > xfrm_dst_cache         0      0    320   25    2 : tunables    0    0    0
> > ip_dst_cache        3048   4116    192   42    2 : tunables    0    0    0
> >
> > During Test:
> >
> > # grep -e Slab -e Free /proc/meminfo
> > MemFree:        29431516 kB
> > Slab:             240940 kB
> >
> > # grep dst_cache /proc/slabinfo
> > ip6_dst_cache      11980  12064    256   32    2 : tunables    0    0    0
> > xfrm_dst_cache         0      0    320   25    2 : tunables    0    0    0
> > ip_dst_cache        3048   4116    192   42    2 : tunables    0    0    0
> >
> > After Test:
> >
> > # grep -e Slab -e Free /proc/meminfo
> > MemFree:        29441816 kB
> > Slab:             238132 kB
> >
> > # grep dst_cache /proc/slabinfo
> > ip6_dst_cache       1902   2432    256   32    2 : tunables    0    0    0
> > xfrm_dst_cache         0      0    320   25    2 : tunables    0    0    0
> > ip_dst_cache        3048   4116    192   42    2 : tunables    0    0    0
> >
> > Tested-by: Andrea Mayer <andrea.mayer@uniroma2.it>
> > Signed-off-by: Jon Maxwell <jmaxwell37@gmail.com>
> > ---
> >  include/net/dst_ops.h |  2 +-
> >  net/core/dst.c        |  8 ++------
> >  net/ipv6/route.c      | 13 +++++--------
> >  3 files changed, 8 insertions(+), 15 deletions(-)
> >
> > diff --git a/include/net/dst_ops.h b/include/net/dst_ops.h
> > index 88ff7bb2bb9b..632086b2f644 100644
> > --- a/include/net/dst_ops.h
> > +++ b/include/net/dst_ops.h
> > @@ -16,7 +16,7 @@ struct dst_ops {
> >       unsigned short          family;
> >       unsigned int            gc_thresh;
> >
> > -     int                     (*gc)(struct dst_ops *ops);
> > +     void                    (*gc)(struct dst_ops *ops);
> >       struct dst_entry *      (*check)(struct dst_entry *, __u32 cookie);
> >       unsigned int            (*default_advmss)(const struct dst_entry *);
> >       unsigned int            (*mtu)(const struct dst_entry *);
> > diff --git a/net/core/dst.c b/net/core/dst.c
> > index 6d2dd03dafa8..31c08a3386d3 100644
> > --- a/net/core/dst.c
> > +++ b/net/core/dst.c
> > @@ -82,12 +82,8 @@ void *dst_alloc(struct dst_ops *ops, struct net_device *dev,
> >
> >       if (ops->gc &&
> >           !(flags & DST_NOCOUNT) &&
> > -         dst_entries_get_fast(ops) > ops->gc_thresh) {
> > -             if (ops->gc(ops)) {
> > -                     pr_notice_ratelimited("Route cache is full: consider increasing sysctl net.ipv6.route.max_size.\n");
> > -                     return NULL;
> > -             }
> > -     }
> > +         dst_entries_get_fast(ops) > ops->gc_thresh)
> > +             ops->gc(ops);
> >
> >       dst = kmem_cache_alloc(ops->kmem_cachep, GFP_ATOMIC);
> >       if (!dst)
> > diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> > index e74e0361fd92..b643dda68d31 100644
> > --- a/net/ipv6/route.c
> > +++ b/net/ipv6/route.c
> > @@ -91,7 +91,7 @@ static struct dst_entry *ip6_negative_advice(struct dst_entry *);
> >  static void          ip6_dst_destroy(struct dst_entry *);
> >  static void          ip6_dst_ifdown(struct dst_entry *,
> >                                      struct net_device *dev, int how);
> > -static int            ip6_dst_gc(struct dst_ops *ops);
> > +static void           ip6_dst_gc(struct dst_ops *ops);
> >
> >  static int           ip6_pkt_discard(struct sk_buff *skb);
> >  static int           ip6_pkt_discard_out(struct net *net, struct sock *sk, struct sk_buff *skb);
> > @@ -3284,11 +3284,10 @@ struct dst_entry *icmp6_dst_alloc(struct net_device *dev,
> >       return dst;
> >  }
> >
> > -static int ip6_dst_gc(struct dst_ops *ops)
> > +static void ip6_dst_gc(struct dst_ops *ops)
> >  {
> >       struct net *net = container_of(ops, struct net, ipv6.ip6_dst_ops);
> >       int rt_min_interval = net->ipv6.sysctl.ip6_rt_gc_min_interval;
> > -     int rt_max_size = net->ipv6.sysctl.ip6_rt_max_size;
> >       int rt_elasticity = net->ipv6.sysctl.ip6_rt_gc_elasticity;
> >       int rt_gc_timeout = net->ipv6.sysctl.ip6_rt_gc_timeout;
> >       unsigned long rt_last_gc = net->ipv6.ip6_rt_last_gc;
> > @@ -3296,11 +3295,10 @@ static int ip6_dst_gc(struct dst_ops *ops)
> >       int entries;
> >
> >       entries = dst_entries_get_fast(ops);
> > -     if (entries > rt_max_size)
> > +     if (entries > ops->gc_thresh)
> >               entries = dst_entries_get_slow(ops);
> >
> > -     if (time_after(rt_last_gc + rt_min_interval, jiffies) &&
> > -         entries <= rt_max_size)
> > +     if (time_after(rt_last_gc + rt_min_interval, jiffies))
> >               goto out;
> >
> >       fib6_run_gc(atomic_inc_return(&net->ipv6.ip6_rt_gc_expire), net, true);
> > @@ -3310,7 +3308,6 @@ static int ip6_dst_gc(struct dst_ops *ops)
> >  out:
> >       val = atomic_read(&net->ipv6.ip6_rt_gc_expire);
> >       atomic_set(&net->ipv6.ip6_rt_gc_expire, val - (val >> rt_elasticity));
> > -     return entries > rt_max_size;
> >  }
> >
> >  static int ip6_nh_lookup_table(struct net *net, struct fib6_config *cfg,
> > @@ -6512,7 +6509,7 @@ static int __net_init ip6_route_net_init(struct net *net)
> >  #endif
> >
> >       net->ipv6.sysctl.flush_delay = 0;
> > -     net->ipv6.sysctl.ip6_rt_max_size = 4096;
> > +     net->ipv6.sysctl.ip6_rt_max_size = INT_MAX;
> >       net->ipv6.sysctl.ip6_rt_gc_min_interval = HZ / 2;
> >       net->ipv6.sysctl.ip6_rt_gc_timeout = 60*HZ;
> >       net->ipv6.sysctl.ip6_rt_gc_interval = 30*HZ;
> > --
> > 2.31.1