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Message-ID: <20130607144833.GB2995@sbohrermbp13-local.rgmadvisors.com>
Date: Fri, 7 Jun 2013 09:48:33 -0500
From: Shawn Bohrer <sbohrer@...advisors.com>
To: Eric Dumazet <eric.dumazet@...il.com>
Cc: netdev@...r.kernel.org, davem@...emloft.net
Subject: Re: Performance regression from routing cache removal?
On Thu, Jun 06, 2013 at 05:35:01PM -0700, Eric Dumazet wrote:
> On Wed, 2013-06-05 at 13:52 -0700, Eric Dumazet wrote:
>
> > It can be easily done, with a threshold :
> >
> > Above say 4 multicast addresses in the mc_list, allocate a hash table
> > and populate it.
>
> Please try the following (untested) patch :
>
> include/linux/igmp.h | 1
> include/linux/inetdevice.h | 5 ++
> net/ipv4/igmp.c | 73 +++++++++++++++++++++++++++++++++--
> 3 files changed, 76 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/igmp.h b/include/linux/igmp.h
> index 7f2bf15..e3362b5 100644
> --- a/include/linux/igmp.h
> +++ b/include/linux/igmp.h
> @@ -84,6 +84,7 @@ struct ip_mc_list {
> struct ip_mc_list *next;
> struct ip_mc_list __rcu *next_rcu;
> };
> + struct ip_mc_list __rcu *next_hash;
> struct timer_list timer;
> int users;
> atomic_t refcnt;
> diff --git a/include/linux/inetdevice.h b/include/linux/inetdevice.h
> index ea1e3b8..b99cd23 100644
> --- a/include/linux/inetdevice.h
> +++ b/include/linux/inetdevice.h
> @@ -50,12 +50,17 @@ struct ipv4_devconf {
> DECLARE_BITMAP(state, IPV4_DEVCONF_MAX);
> };
>
> +#define MC_HASH_SZ_LOG 9
> +
> struct in_device {
> struct net_device *dev;
> atomic_t refcnt;
> int dead;
> struct in_ifaddr *ifa_list; /* IP ifaddr chain */
> +
> struct ip_mc_list __rcu *mc_list; /* IP multicast filter chain */
> + struct ip_mc_list __rcu * __rcu *mc_hash;
> +
> int mc_count; /* Number of installed mcasts */
> spinlock_t mc_tomb_lock;
> struct ip_mc_list *mc_tomb;
> diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
> index 450f625..9c60482 100644
> --- a/net/ipv4/igmp.c
> +++ b/net/ipv4/igmp.c
> @@ -1217,6 +1217,56 @@ static void igmp_group_added(struct ip_mc_list *im)
> * Multicast list managers
> */
>
> +static u32 ip_mc_hash(const struct ip_mc_list *im)
> +{
> + return hash_32((u32)im->multiaddr, MC_HASH_SZ_LOG);
> +}
> +
> +static void ip_mc_hash_add(struct in_device *in_dev,
> + struct ip_mc_list *im)
> +{
> + struct ip_mc_list __rcu **mc_hash;
> + u32 hash;
> +
> + mc_hash = rtnl_dereference(in_dev->mc_hash);
> + if (mc_hash) {
> + hash = ip_mc_hash(im);
> + im->next_hash = rtnl_dereference(mc_hash[hash]);
> + rcu_assign_pointer(mc_hash[hash], im);
> + } else if (in_dev->mc_count >= 4) {
> + mc_hash = kzalloc(sizeof(struct ip_mc_list *) << MC_HASH_SZ_LOG,
> + GFP_KERNEL);
> + if (mc_hash) {
> + struct ip_mc_list *aux = rtnl_dereference(in_dev->mc_list);
> +
> + while (aux) {
> + hash = ip_mc_hash(aux);
> +
> + aux->next_hash = rcu_dereference_protected(mc_hash[hash], 1);
> + RCU_INIT_POINTER(mc_hash[hash], aux);
> + aux = rtnl_dereference(aux->next_rcu);
> + }
> + rcu_assign_pointer(in_dev->mc_hash, mc_hash);
> + }
> + }
> +}
> +
> +static void ip_mc_hash_remove(struct in_device *in_dev,
> + struct ip_mc_list *im)
> +{
> + struct ip_mc_list __rcu **mc_hash = rtnl_dereference(in_dev->mc_hash);
> + struct ip_mc_list *aux;
> + unsigned int hash;
> +
> + if (!mc_hash)
> + return;
> + hash = ip_mc_hash(im);
> + mc_hash += hash;
> + while ((aux = rtnl_dereference(*mc_hash)) != im)
> + mc_hash = &aux->next_hash;
> + *mc_hash = im->next_hash;
> +}
> +
>
> /*
> * A socket has joined a multicast group on device dev.
> @@ -1258,6 +1308,8 @@ void ip_mc_inc_group(struct in_device *in_dev, __be32 addr)
> in_dev->mc_count++;
> rcu_assign_pointer(in_dev->mc_list, im);
>
> + ip_mc_hash_add(in_dev, im);
> +
> #ifdef CONFIG_IP_MULTICAST
> igmpv3_del_delrec(in_dev, im->multiaddr);
> #endif
> @@ -1314,6 +1366,7 @@ void ip_mc_dec_group(struct in_device *in_dev, __be32 addr)
> ip = &i->next_rcu) {
> if (i->multiaddr == addr) {
> if (--i->users == 0) {
> + ip_mc_hash_remove(in_dev, i);
> *ip = i->next_rcu;
> in_dev->mc_count--;
> igmp_group_dropped(i);
> @@ -1431,6 +1484,7 @@ void ip_mc_destroy_dev(struct in_device *in_dev)
> ip_mc_clear_src(i);
> ip_ma_put(i);
> }
> + kfree(in_dev->mc_hash);
> }
>
> /* RTNL is locked */
> @@ -2321,12 +2375,25 @@ void ip_mc_drop_socket(struct sock *sk)
> int ip_check_mc_rcu(struct in_device *in_dev, __be32 mc_addr, __be32 src_addr, u16 proto)
> {
> struct ip_mc_list *im;
> + struct ip_mc_list __rcu **mc_hash;
> struct ip_sf_list *psf;
> int rv = 0;
>
> - for_each_pmc_rcu(in_dev, im) {
> - if (im->multiaddr == mc_addr)
> - break;
> + mc_hash = rcu_dereference(in_dev->mc_hash);
> + if (mc_hash) {
> + u32 hash = hash_32((u32)mc_addr, MC_HASH_SZ_LOG);
> +
> + for (im = rcu_dereference(mc_hash[hash]);
> + im != NULL;
> + im = rcu_dereference(im->next_hash)) {
> + if (im->multiaddr == mc_addr)
> + break;
> + }
> + } else {
> + for_each_pmc_rcu(in_dev, im) {
> + if (im->multiaddr == mc_addr)
> + break;
> + }
> }
> if (im && proto == IPPROTO_IGMP) {
> rv = 1;
>
>
Thanks Eric! I ran this patch last night and it greatly improves the
multicast receive performance on 3.10-rc4. 3.10 may still be 1-2us
slower than 3.4 but it is a little hard for me to tell at the moment
since it looks like there is a mmapped I/O regression in 3.10 that I
also need to track down.
--
Shawn
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