Re: [PATCH net-next] ipvs: make ip_vs_svc_table and ip_vs_svc_fwm_table per netns

	Hello,

On Fri, 7 Jul 2023, Dust Li wrote:

> From: Jiejian Wu <[email protected]>
> 
> Current ipvs uses one global mutex "__ip_vs_mutex" to keep the global
> "ip_vs_svc_table" and "ip_vs_svc_fwm_table" safe. But when there are
> tens of thousands of services from different netns in the table, it
> takes a long time to look up the table, for example, using "ipvsadm
> -ln" from different netns simultaneously.
> 
> We make "ip_vs_svc_table" and "ip_vs_svc_fwm_table" per netns, and we
> add "service_mutex" per netns to keep these two tables safe instead of
> the global "__ip_vs_mutex" in current version. To this end, looking up
> services from different netns simultaneously will not get stuck,
> shortening the time consumption in large-scale deployment. Evaluation
> methods and results are provided below.
> 
> init.sh: #!/bin/bash
> for((i=1;i<=4;i++));do
>         ip netns add ns$i
>         ip netns exec ns$i ip link set dev lo up
>         ip netns exec ns$i sh add-services.sh
> done
> 
> add-services.sh: #!/bin/bash
> for((i=0;i<30000;i++)); do
>         ipvsadm -A  -t 10.10.10.10:$((80+$i)) -s rr
> done
> 
> runtest.sh: #!/bin/bash
> for((i=1;i<4;i++));do
>         ip netns exec ns$i ipvsadm -ln > /dev/null &
> done
> ip netns exec ns4 ipvsadm -ln > /dev/null
> 
> Run "sh init.sh" to initiate the network environment. Then run "time
> ./runtest.sh" to evaluate the time consumption. Our testbed is a 4-core
> Intel Xeon ECS. The result of the original version is around 8 seconds,
> while the result of the modified version is only 0.8 seconds.
> 
> Signed-off-by: Jiejian Wu <[email protected]>
> Co-developed-by: Dust Li <[email protected]>
> Signed-off-by: Dust Li <[email protected]>
> ---
>  include/net/ip_vs.h            |  12 ++++
>  net/netfilter/ipvs/ip_vs_ctl.c | 109 +++++++++++++++------------------
>  2 files changed, 62 insertions(+), 59 deletions(-)
> 
> diff --git a/include/net/ip_vs.h b/include/net/ip_vs.h
> index ff406ef4fd4aa..83ab2db4a994b 100644
> --- a/include/net/ip_vs.h
> +++ b/include/net/ip_vs.h
> @@ -33,6 +33,12 @@
>  
>  #define IP_VS_HDR_INVERSE	1
>  #define IP_VS_HDR_ICMP		2
> +/*
> + *	Hash table: for virtual service lookups
> + */
> +#define IP_VS_SVC_TAB_BITS 8
> +#define IP_VS_SVC_TAB_SIZE (1 << IP_VS_SVC_TAB_BITS)
> +#define IP_VS_SVC_TAB_MASK (IP_VS_SVC_TAB_SIZE - 1)
>  
>  /* Generic access of ipvs struct */
>  static inline struct netns_ipvs *net_ipvs(struct net* net)
> @@ -1041,6 +1047,12 @@ struct netns_ipvs {
>  	 */
>  	unsigned int		mixed_address_family_dests;
>  	unsigned int		hooks_afmask;	/* &1=AF_INET, &2=AF_INET6 */
> +
> +	struct mutex service_mutex;
> +	/* the service table hashed by <protocol, addr, port> */
> +	struct hlist_head ip_vs_svc_table[IP_VS_SVC_TAB_SIZE];
> +	/* the service table hashed by fwmark */
> +	struct hlist_head ip_vs_svc_fwm_table[IP_VS_SVC_TAB_SIZE];

	Can we use svc_table and svc_fwm_table for the table names?

>  };
>  
>  #define DEFAULT_SYNC_THRESHOLD	3
> diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
> index 62606fb44d027..c8b30f9ec5106 100644
> --- a/net/netfilter/ipvs/ip_vs_ctl.c
> +++ b/net/netfilter/ipvs/ip_vs_ctl.c

> @@ -414,7 +404,7 @@ __ip_vs_service_find(struct netns_ipvs *ipvs, int af, __u16 protocol,
>  	/* Check for "full" addressed entries */
>  	hash = ip_vs_svc_hashkey(ipvs, af, protocol, vaddr, vport);
>  
> -	hlist_for_each_entry_rcu(svc, &ip_vs_svc_table[hash], s_list) {
> +	hlist_for_each_entry_rcu(svc, &ipvs->ip_vs_svc_table[hash], s_list) {
>  		if ((svc->af == af)
>  		    && ip_vs_addr_equal(af, &svc->addr, vaddr)
>  		    && (svc->port == vport)
> @@ -441,7 +431,7 @@ __ip_vs_svc_fwm_find(struct netns_ipvs *ipvs, int af, __u32 fwmark)
>  	/* Check for fwmark addressed entries */
>  	hash = ip_vs_svc_fwm_hashkey(ipvs, fwmark);
>  
> -	hlist_for_each_entry_rcu(svc, &ip_vs_svc_fwm_table[hash], f_list) {
> +	hlist_for_each_entry_rcu(svc, &ipvs->ip_vs_svc_fwm_table[hash], f_list) {
>  		if (svc->fwmark == fwmark && svc->af == af
>  		    && (svc->ipvs == ipvs)) {

	__ip_vs_service_find and __ip_vs_svc_fwm_find: match
by svc->ipvs is not needed anymore. There are other svc->ipvs == ipvs
checks in this file.

> @@ -1732,12 +1722,12 @@ void ip_vs_service_nets_cleanup(struct list_head *net_list)
>  	struct net *net;
>  
>  	/* Check for "full" addressed entries */
> -	mutex_lock(&__ip_vs_mutex);
>  	list_for_each_entry(net, net_list, exit_list) {
>  		ipvs = net_ipvs(net);
> +		mutex_lock(&ipvs->service_mutex);
>  		ip_vs_flush(ipvs, true);
> +		mutex_unlock(&ipvs->service_mutex);
>  	}
> -	mutex_unlock(&__ip_vs_mutex);

	This reverts speedups from commit 5d5a0815f854 but with some
reordering we probably can remove the mutex completely as part from
further optimizations.

>  }
>  
>  /* Put all references for device (dst_cache) */
> @@ -1775,9 +1765,9 @@ static int ip_vs_dst_event(struct notifier_block *this, unsigned long event,
>  	if (event != NETDEV_DOWN || !ipvs)
>  		return NOTIFY_DONE;
>  	IP_VS_DBG(3, "%s() dev=%s\n", __func__, dev->name);
> -	mutex_lock(&__ip_vs_mutex);
> +	mutex_lock(&ipvs->service_mutex);

	Looks like with global notifier we have a problem where 
ip_vs_dst_event() can not know if net->ipvs is not in process
of freeing from another CPU. The global __ip_vs_mutex helped
to avoid the problem, if we see svc then svc->ipvs is valid.
But now even the ipvs->dest_trash_lock access looks under risk.
Probably, we should switch to register_netdevice_notifier_net,
so that ip_vs_dst_event() can safely work with the ipvs struct.
At first look, unregister_netdevice_notifier_net() should be
called in ip_vs_control_net_cleanup() just after the
ip_vs_trash_cleanup() call. A drawback is that when we unregister
from netns exit context __unregister_netdevice_notifier_net()
still calls call_netdevice_unregister_net_notifiers, something
that we do not want. May be we can silence these events with
some new wrapper/parameter.

> @@ -2303,9 +2293,9 @@ static struct ip_vs_service *ip_vs_info_array(struct seq_file *seq, loff_t pos)
>  
>  	/* look in hash by protocol */
>  	for (idx = 0; idx < IP_VS_SVC_TAB_SIZE; idx++) {
> -		hlist_for_each_entry_rcu(svc, &ip_vs_svc_table[idx], s_list) {
> +		hlist_for_each_entry_rcu(svc, &ipvs->ip_vs_svc_table[idx], s_list) {
>  			if ((svc->ipvs == ipvs) && pos-- == 0) {
> -				iter->table = ip_vs_svc_table;
> +				iter->table = ipvs->ip_vs_svc_table;

	We can change iter->table to int table_id, 0 (ip_vs_svc_table)
and 1 (ip_vs_svc_fwm_table), for all these ip_vs_info_* funcs.

>  				iter->bucket = idx;
>  				return svc;
>  			}
> @@ -2314,10 +2304,10 @@ static struct ip_vs_service *ip_vs_info_array(struct seq_file *seq, loff_t pos)
>  
>  	/* keep looking in fwmark */
>  	for (idx = 0; idx < IP_VS_SVC_TAB_SIZE; idx++) {
> -		hlist_for_each_entry_rcu(svc, &ip_vs_svc_fwm_table[idx],
> +		hlist_for_each_entry_rcu(svc, &ipvs->ip_vs_svc_fwm_table[idx],
>  					 f_list) {
>  			if ((svc->ipvs == ipvs) && pos-- == 0) {
> -				iter->table = ip_vs_svc_fwm_table;
> +				iter->table = ipvs->ip_vs_svc_fwm_table;
>  				iter->bucket = idx;
>  				return svc;
>  			}

> @@ -3058,7 +3050,7 @@ do_ip_vs_get_ctl(struct sock *sk, int cmd, void __user *user, int *len)
>  		return ret;
>  	}
>  
> -	mutex_lock(&__ip_vs_mutex);
> +	mutex_lock(&ipvs->service_mutex);
>  	switch (cmd) {
>  	case IP_VS_SO_GET_VERSION:
>  	{
> @@ -3157,7 +3149,7 @@ do_ip_vs_get_ctl(struct sock *sk, int cmd, void __user *user, int *len)
>  	}
>  
>  out:
> -	mutex_unlock(&__ip_vs_mutex);
> +	mutex_unlock(&ipvs->service_mutex);
>  	return ret;
>  }
>  
> @@ -3392,9 +3384,9 @@ static int ip_vs_genl_dump_services(struct sk_buff *skb,
>  	struct net *net = sock_net(skb->sk);
>  	struct netns_ipvs *ipvs = net_ipvs(net);
>  
> -	mutex_lock(&__ip_vs_mutex);
> +	mutex_lock(&ipvs->service_mutex);

	While do_ip_vs_get_ctl is a reader that can block we
can not use RCU but in ip_vs_genl_dump_services() we can replace
the __ip_vs_mutex with rcu_read_lock because we just fill the skb.

>  	for (i = 0; i < IP_VS_SVC_TAB_SIZE; i++) {
> -		hlist_for_each_entry(svc, &ip_vs_svc_table[i], s_list) {
> +		hlist_for_each_entry(svc, &ipvs->ip_vs_svc_table[i], s_list) {
>  			if (++idx <= start || (svc->ipvs != ipvs))
>  				continue;
>  			if (ip_vs_genl_dump_service(skb, svc, cb) < 0) {
> @@ -3405,7 +3397,7 @@ static int ip_vs_genl_dump_services(struct sk_buff *skb,
>  	}
>  
>  	for (i = 0; i < IP_VS_SVC_TAB_SIZE; i++) {
> -		hlist_for_each_entry(svc, &ip_vs_svc_fwm_table[i], f_list) {
> +		hlist_for_each_entry(svc, &ipvs->ip_vs_svc_fwm_table[i], f_list) {
>  			if (++idx <= start || (svc->ipvs != ipvs))
>  				continue;
>  			if (ip_vs_genl_dump_service(skb, svc, cb) < 0) {
> @@ -3416,7 +3408,7 @@ static int ip_vs_genl_dump_services(struct sk_buff *skb,
>  	}
>  
>  nla_put_failure:
> -	mutex_unlock(&__ip_vs_mutex);
> +	mutex_unlock(&ipvs->service_mutex);
>  	cb->args[0] = idx;
>  
>  	return skb->len;
> @@ -3605,7 +3597,7 @@ static int ip_vs_genl_dump_dests(struct sk_buff *skb,
>  	struct net *net = sock_net(skb->sk);
>  	struct netns_ipvs *ipvs = net_ipvs(net);
>  
> -	mutex_lock(&__ip_vs_mutex);
> +	mutex_lock(&ipvs->service_mutex);

	In ip_vs_genl_dump_dests() we can use RCU too but there
will be probably double rcu_read_lock in ip_vs_genl_parse_service(),
so rcu_read_lock can be moved into the top caller.

>  
>  	/* Try to find the service for which to dump destinations */
>  	if (nlmsg_parse_deprecated(cb->nlh, GENL_HDRLEN, attrs, IPVS_CMD_ATTR_MAX, ip_vs_cmd_policy, cb->extack))
> @@ -3630,7 +3622,7 @@ static int ip_vs_genl_dump_dests(struct sk_buff *skb,
>  	cb->args[0] = idx;
>  
>  out_err:
> -	mutex_unlock(&__ip_vs_mutex);
> +	mutex_unlock(&ipvs->service_mutex);
>  
>  	return skb->len;
>  }

> @@ -4058,7 +4050,7 @@ static int ip_vs_genl_get_cmd(struct sk_buff *skb, struct genl_info *info)
>  	if (!msg)
>  		return -ENOMEM;
>  
> -	mutex_lock(&__ip_vs_mutex);
> +	mutex_lock(&ipvs->service_mutex);

	ip_vs_genl_get_cmd is another place that we can use RCU.

>  
>  	reply = genlmsg_put_reply(msg, info, &ip_vs_genl_family, 0, reply_cmd);
>  	if (reply == NULL)
> @@ -4126,7 +4118,7 @@ static int ip_vs_genl_get_cmd(struct sk_buff *skb, struct genl_info *info)
>  out_err:
>  	nlmsg_free(msg);
>  out:
> -	mutex_unlock(&__ip_vs_mutex);
> +	mutex_unlock(&ipvs->service_mutex);
>  
>  	return ret;
>  }

	Note that ip_vs_est.c uses __ip_vs_mutex too, it should be
changed to service_mutex. Do not keep __ip_vs_mutex anymore.

	Also, there is more work if we want independent
namespaces and to give power to users:

- account memory: GFP_KERNEL -> GFP_KERNEL_ACCOUNT

- the connections table is still global but it should be possible
to make all tables per-net and to grow on load from NULL to max bits

- convert GENL_ADMIN_PERM -> GENL_UNS_ADMIN_PERM and make
sysctls visible to other namespaces

	If the plan is to have multiple netns loaded with many
conns may be I can follow your patch with more optimization
patches.

Regards

--
Julian Anastasov <[email protected]>