net dst: use a percpu_counter to track entries
Eric Dumazet [Fri, 8 Oct 2010 06:37:34 +0000 (06:37 +0000)]
struct dst_ops tracks number of allocated dst in an atomic_t field,
subject to high cache line contention in stress workload.

Switch to a percpu_counter, to reduce number of time we need to dirty a
central location. Place it on a separate cache line to avoid dirtying
read only fields.

Stress test :

(Sending 160.000.000 UDP frames,
IP route cache disabled, dual E5540 @2.53GHz,
32bit kernel, FIB_TRIE, SLUB/NUMA)

Before:

real    0m51.179s
user    0m15.329s
sys     10m15.942s

After:

real 0m45.570s
user 0m15.525s
sys 9m56.669s

With a small reordering of struct neighbour fields, subject of a
following patch, (to separate refcnt from other read mostly fields)

real 0m41.841s
user 0m15.261s
sys 8m45.949s

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/dst_ops.h
net/bridge/br_netfilter.c
net/core/dst.c
net/decnet/dn_route.c
net/ipv4/route.c
net/ipv4/xfrm4_policy.c
net/ipv6/route.c
net/ipv6/xfrm6_policy.c

index d1ff9b7..1fa5306 100644 (file)
@@ -1,6 +1,7 @@
 #ifndef _NET_DST_OPS_H
 #define _NET_DST_OPS_H
 #include <linux/types.h>
+#include <linux/percpu_counter.h>
 
 struct dst_entry;
 struct kmem_cachep;
@@ -22,7 +23,41 @@ struct dst_ops {
        void                    (*update_pmtu)(struct dst_entry *dst, u32 mtu);
        int                     (*local_out)(struct sk_buff *skb);
 
-       atomic_t                entries;
        struct kmem_cache       *kmem_cachep;
+
+       struct percpu_counter   pcpuc_entries ____cacheline_aligned_in_smp;
 };
+
+static inline int dst_entries_get_fast(struct dst_ops *dst)
+{
+       return percpu_counter_read_positive(&dst->pcpuc_entries);
+}
+
+static inline int dst_entries_get_slow(struct dst_ops *dst)
+{
+       int res;
+
+       local_bh_disable();
+       res = percpu_counter_sum_positive(&dst->pcpuc_entries);
+       local_bh_enable();
+       return res;
+}
+
+static inline void dst_entries_add(struct dst_ops *dst, int val)
+{
+       local_bh_disable();
+       percpu_counter_add(&dst->pcpuc_entries, val);
+       local_bh_enable();
+}
+
+static inline int dst_entries_init(struct dst_ops *dst)
+{
+       return percpu_counter_init(&dst->pcpuc_entries, 0);
+}
+
+static inline void dst_entries_destroy(struct dst_ops *dst)
+{
+       percpu_counter_destroy(&dst->pcpuc_entries);
+}
+
 #endif
index 77f7b5f..7f9ce96 100644 (file)
@@ -106,7 +106,6 @@ static struct dst_ops fake_dst_ops = {
        .family =               AF_INET,
        .protocol =             cpu_to_be16(ETH_P_IP),
        .update_pmtu =          fake_update_pmtu,
-       .entries =              ATOMIC_INIT(0),
 };
 
 /*
@@ -1003,15 +1002,22 @@ int __init br_netfilter_init(void)
 {
        int ret;
 
-       ret = nf_register_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
+       ret = dst_entries_init(&fake_dst_ops);
        if (ret < 0)
                return ret;
+
+       ret = nf_register_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
+       if (ret < 0) {
+               dst_entries_destroy(&fake_dst_ops);
+               return ret;
+       }
 #ifdef CONFIG_SYSCTL
        brnf_sysctl_header = register_sysctl_paths(brnf_path, brnf_table);
        if (brnf_sysctl_header == NULL) {
                printk(KERN_WARNING
                       "br_netfilter: can't register to sysctl.\n");
                nf_unregister_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
+               dst_entries_destroy(&fake_dst_ops);
                return -ENOMEM;
        }
 #endif
@@ -1025,4 +1031,5 @@ void br_netfilter_fini(void)
 #ifdef CONFIG_SYSCTL
        unregister_sysctl_table(brnf_sysctl_header);
 #endif
+       dst_entries_destroy(&fake_dst_ops);
 }
index 978a1ee..32e542d 100644 (file)
@@ -168,7 +168,7 @@ void *dst_alloc(struct dst_ops *ops)
 {
        struct dst_entry *dst;
 
-       if (ops->gc && atomic_read(&ops->entries) > ops->gc_thresh) {
+       if (ops->gc && dst_entries_get_fast(ops) > ops->gc_thresh) {
                if (ops->gc(ops))
                        return NULL;
        }
@@ -183,7 +183,7 @@ void *dst_alloc(struct dst_ops *ops)
 #if RT_CACHE_DEBUG >= 2
        atomic_inc(&dst_total);
 #endif
-       atomic_inc(&ops->entries);
+       dst_entries_add(ops, 1);
        return dst;
 }
 EXPORT_SYMBOL(dst_alloc);
@@ -236,7 +236,7 @@ again:
                neigh_release(neigh);
        }
 
-       atomic_dec(&dst->ops->entries);
+       dst_entries_add(dst->ops, -1);
 
        if (dst->ops->destroy)
                dst->ops->destroy(dst);
index 6585ea6..df0f3e5 100644 (file)
@@ -132,7 +132,6 @@ static struct dst_ops dn_dst_ops = {
        .negative_advice =      dn_dst_negative_advice,
        .link_failure =         dn_dst_link_failure,
        .update_pmtu =          dn_dst_update_pmtu,
-       .entries =              ATOMIC_INIT(0),
 };
 
 static __inline__ unsigned dn_hash(__le16 src, __le16 dst)
@@ -1758,6 +1757,7 @@ void __init dn_route_init(void)
        dn_dst_ops.kmem_cachep =
                kmem_cache_create("dn_dst_cache", sizeof(struct dn_route), 0,
                                  SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
+       dst_entries_init(&dn_dst_ops);
        setup_timer(&dn_route_timer, dn_dst_check_expire, 0);
        dn_route_timer.expires = jiffies + decnet_dst_gc_interval * HZ;
        add_timer(&dn_route_timer);
@@ -1816,5 +1816,6 @@ void __exit dn_route_cleanup(void)
        dn_run_flush(0);
 
        proc_net_remove(&init_net, "decnet_cache");
+       dst_entries_destroy(&dn_dst_ops);
 }
 
index 3888f6b..0755aa4 100644 (file)
@@ -159,7 +159,6 @@ static struct dst_ops ipv4_dst_ops = {
        .link_failure =         ipv4_link_failure,
        .update_pmtu =          ip_rt_update_pmtu,
        .local_out =            __ip_local_out,
-       .entries =              ATOMIC_INIT(0),
 };
 
 #define ECN_OR_COST(class)     TC_PRIO_##class
@@ -466,7 +465,7 @@ static int rt_cpu_seq_show(struct seq_file *seq, void *v)
 
        seq_printf(seq,"%08x  %08x %08x %08x %08x %08x %08x %08x "
                   " %08x %08x %08x %08x %08x %08x %08x %08x %08x \n",
-                  atomic_read(&ipv4_dst_ops.entries),
+                  dst_entries_get_slow(&ipv4_dst_ops),
                   st->in_hit,
                   st->in_slow_tot,
                   st->in_slow_mc,
@@ -945,6 +944,7 @@ static int rt_garbage_collect(struct dst_ops *ops)
        struct rtable *rth, **rthp;
        unsigned long now = jiffies;
        int goal;
+       int entries = dst_entries_get_fast(&ipv4_dst_ops);
 
        /*
         * Garbage collection is pretty expensive,
@@ -954,28 +954,28 @@ static int rt_garbage_collect(struct dst_ops *ops)
        RT_CACHE_STAT_INC(gc_total);
 
        if (now - last_gc < ip_rt_gc_min_interval &&
-           atomic_read(&ipv4_dst_ops.entries) < ip_rt_max_size) {
+           entries < ip_rt_max_size) {
                RT_CACHE_STAT_INC(gc_ignored);
                goto out;
        }
 
+       entries = dst_entries_get_slow(&ipv4_dst_ops);
        /* Calculate number of entries, which we want to expire now. */
-       goal = atomic_read(&ipv4_dst_ops.entries) -
-               (ip_rt_gc_elasticity << rt_hash_log);
+       goal = entries - (ip_rt_gc_elasticity << rt_hash_log);
        if (goal <= 0) {
                if (equilibrium < ipv4_dst_ops.gc_thresh)
                        equilibrium = ipv4_dst_ops.gc_thresh;
-               goal = atomic_read(&ipv4_dst_ops.entries) - equilibrium;
+               goal = entries - equilibrium;
                if (goal > 0) {
                        equilibrium += min_t(unsigned int, goal >> 1, rt_hash_mask + 1);
-                       goal = atomic_read(&ipv4_dst_ops.entries) - equilibrium;
+                       goal = entries - equilibrium;
                }
        } else {
                /* We are in dangerous area. Try to reduce cache really
                 * aggressively.
                 */
                goal = max_t(unsigned int, goal >> 1, rt_hash_mask + 1);
-               equilibrium = atomic_read(&ipv4_dst_ops.entries) - goal;
+               equilibrium = entries - goal;
        }
 
        if (now - last_gc >= ip_rt_gc_min_interval)
@@ -1032,14 +1032,16 @@ static int rt_garbage_collect(struct dst_ops *ops)
                expire >>= 1;
 #if RT_CACHE_DEBUG >= 2
                printk(KERN_DEBUG "expire>> %u %d %d %d\n", expire,
-                               atomic_read(&ipv4_dst_ops.entries), goal, i);
+                               dst_entries_get_fast(&ipv4_dst_ops), goal, i);
 #endif
 
-               if (atomic_read(&ipv4_dst_ops.entries) < ip_rt_max_size)
+               if (dst_entries_get_fast(&ipv4_dst_ops) < ip_rt_max_size)
                        goto out;
        } while (!in_softirq() && time_before_eq(jiffies, now));
 
-       if (atomic_read(&ipv4_dst_ops.entries) < ip_rt_max_size)
+       if (dst_entries_get_fast(&ipv4_dst_ops) < ip_rt_max_size)
+               goto out;
+       if (dst_entries_get_slow(&ipv4_dst_ops) < ip_rt_max_size)
                goto out;
        if (net_ratelimit())
                printk(KERN_WARNING "dst cache overflow\n");
@@ -1049,11 +1051,12 @@ static int rt_garbage_collect(struct dst_ops *ops)
 work_done:
        expire += ip_rt_gc_min_interval;
        if (expire > ip_rt_gc_timeout ||
-           atomic_read(&ipv4_dst_ops.entries) < ipv4_dst_ops.gc_thresh)
+           dst_entries_get_fast(&ipv4_dst_ops) < ipv4_dst_ops.gc_thresh ||
+           dst_entries_get_slow(&ipv4_dst_ops) < ipv4_dst_ops.gc_thresh)
                expire = ip_rt_gc_timeout;
 #if RT_CACHE_DEBUG >= 2
        printk(KERN_DEBUG "expire++ %u %d %d %d\n", expire,
-                       atomic_read(&ipv4_dst_ops.entries), goal, rover);
+                       dst_entries_get_fast(&ipv4_dst_ops), goal, rover);
 #endif
 out:   return 0;
 }
@@ -2717,7 +2720,6 @@ static struct dst_ops ipv4_dst_blackhole_ops = {
        .destroy                =       ipv4_dst_destroy,
        .check                  =       ipv4_blackhole_dst_check,
        .update_pmtu            =       ipv4_rt_blackhole_update_pmtu,
-       .entries                =       ATOMIC_INIT(0),
 };
 
 
@@ -3287,6 +3289,12 @@ int __init ip_rt_init(void)
 
        ipv4_dst_blackhole_ops.kmem_cachep = ipv4_dst_ops.kmem_cachep;
 
+       if (dst_entries_init(&ipv4_dst_ops) < 0)
+               panic("IP: failed to allocate ipv4_dst_ops counter\n");
+
+       if (dst_entries_init(&ipv4_dst_blackhole_ops) < 0)
+               panic("IP: failed to allocate ipv4_dst_blackhole_ops counter\n");
+
        rt_hash_table = (struct rt_hash_bucket *)
                alloc_large_system_hash("IP route cache",
                                        sizeof(struct rt_hash_bucket),
index a580349..4464f3b 100644 (file)
@@ -174,7 +174,7 @@ static inline int xfrm4_garbage_collect(struct dst_ops *ops)
        struct net *net = container_of(ops, struct net, xfrm.xfrm4_dst_ops);
 
        xfrm4_policy_afinfo.garbage_collect(net);
-       return (atomic_read(&ops->entries) > ops->gc_thresh * 2);
+       return (dst_entries_get_slow(ops) > ops->gc_thresh * 2);
 }
 
 static void xfrm4_update_pmtu(struct dst_entry *dst, u32 mtu)
@@ -232,7 +232,6 @@ static struct dst_ops xfrm4_dst_ops = {
        .ifdown =               xfrm4_dst_ifdown,
        .local_out =            __ip_local_out,
        .gc_thresh =            1024,
-       .entries =              ATOMIC_INIT(0),
 };
 
 static struct xfrm_policy_afinfo xfrm4_policy_afinfo = {
@@ -288,6 +287,7 @@ void __init xfrm4_init(int rt_max_size)
         * and start cleaning when were 1/2 full
         */
        xfrm4_dst_ops.gc_thresh = rt_max_size/2;
+       dst_entries_init(&xfrm4_dst_ops);
 
        xfrm4_state_init();
        xfrm4_policy_init();
index 17e2179..25661f9 100644 (file)
@@ -109,7 +109,6 @@ static struct dst_ops ip6_dst_ops_template = {
        .link_failure           =       ip6_link_failure,
        .update_pmtu            =       ip6_rt_update_pmtu,
        .local_out              =       __ip6_local_out,
-       .entries                =       ATOMIC_INIT(0),
 };
 
 static void ip6_rt_blackhole_update_pmtu(struct dst_entry *dst, u32 mtu)
@@ -122,7 +121,6 @@ static struct dst_ops ip6_dst_blackhole_ops = {
        .destroy                =       ip6_dst_destroy,
        .check                  =       ip6_dst_check,
        .update_pmtu            =       ip6_rt_blackhole_update_pmtu,
-       .entries                =       ATOMIC_INIT(0),
 };
 
 static struct rt6_info ip6_null_entry_template = {
@@ -1058,19 +1056,22 @@ static int ip6_dst_gc(struct dst_ops *ops)
        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;
+       int entries;
 
+       entries = dst_entries_get_fast(ops);
        if (time_after(rt_last_gc + rt_min_interval, now) &&
-           atomic_read(&ops->entries) <= rt_max_size)
+           entries <= rt_max_size)
                goto out;
 
        net->ipv6.ip6_rt_gc_expire++;
        fib6_run_gc(net->ipv6.ip6_rt_gc_expire, net);
        net->ipv6.ip6_rt_last_gc = now;
-       if (atomic_read(&ops->entries) < ops->gc_thresh)
+       entries = dst_entries_get_slow(ops);
+       if (entries < ops->gc_thresh)
                net->ipv6.ip6_rt_gc_expire = rt_gc_timeout>>1;
 out:
        net->ipv6.ip6_rt_gc_expire -= net->ipv6.ip6_rt_gc_expire>>rt_elasticity;
-       return atomic_read(&ops->entries) > rt_max_size;
+       return entries > rt_max_size;
 }
 
 /* Clean host part of a prefix. Not necessary in radix tree,
@@ -2524,7 +2525,7 @@ static int rt6_stats_seq_show(struct seq_file *seq, void *v)
                   net->ipv6.rt6_stats->fib_rt_alloc,
                   net->ipv6.rt6_stats->fib_rt_entries,
                   net->ipv6.rt6_stats->fib_rt_cache,
-                  atomic_read(&net->ipv6.ip6_dst_ops.entries),
+                  dst_entries_get_slow(&net->ipv6.ip6_dst_ops),
                   net->ipv6.rt6_stats->fib_discarded_routes);
 
        return 0;
@@ -2666,11 +2667,14 @@ static int __net_init ip6_route_net_init(struct net *net)
        memcpy(&net->ipv6.ip6_dst_ops, &ip6_dst_ops_template,
               sizeof(net->ipv6.ip6_dst_ops));
 
+       if (dst_entries_init(&net->ipv6.ip6_dst_ops) < 0)
+               goto out_ip6_dst_ops;
+
        net->ipv6.ip6_null_entry = kmemdup(&ip6_null_entry_template,
                                           sizeof(*net->ipv6.ip6_null_entry),
                                           GFP_KERNEL);
        if (!net->ipv6.ip6_null_entry)
-               goto out_ip6_dst_ops;
+               goto out_ip6_dst_entries;
        net->ipv6.ip6_null_entry->dst.path =
                (struct dst_entry *)net->ipv6.ip6_null_entry;
        net->ipv6.ip6_null_entry->dst.ops = &net->ipv6.ip6_dst_ops;
@@ -2720,6 +2724,8 @@ out_ip6_prohibit_entry:
 out_ip6_null_entry:
        kfree(net->ipv6.ip6_null_entry);
 #endif
+out_ip6_dst_entries:
+       dst_entries_destroy(&net->ipv6.ip6_dst_ops);
 out_ip6_dst_ops:
        goto out;
 }
@@ -2758,10 +2764,14 @@ int __init ip6_route_init(void)
        if (!ip6_dst_ops_template.kmem_cachep)
                goto out;
 
-       ret = register_pernet_subsys(&ip6_route_net_ops);
+       ret = dst_entries_init(&ip6_dst_blackhole_ops);
        if (ret)
                goto out_kmem_cache;
 
+       ret = register_pernet_subsys(&ip6_route_net_ops);
+       if (ret)
+               goto out_dst_entries;
+
        ip6_dst_blackhole_ops.kmem_cachep = ip6_dst_ops_template.kmem_cachep;
 
        /* Registering of the loopback is done before this portion of code,
@@ -2808,6 +2818,8 @@ out_fib6_init:
        fib6_gc_cleanup();
 out_register_subsys:
        unregister_pernet_subsys(&ip6_route_net_ops);
+out_dst_entries:
+       dst_entries_destroy(&ip6_dst_blackhole_ops);
 out_kmem_cache:
        kmem_cache_destroy(ip6_dst_ops_template.kmem_cachep);
        goto out;
index 39676ea..7e74023 100644 (file)
@@ -199,7 +199,7 @@ static inline int xfrm6_garbage_collect(struct dst_ops *ops)
        struct net *net = container_of(ops, struct net, xfrm.xfrm6_dst_ops);
 
        xfrm6_policy_afinfo.garbage_collect(net);
-       return atomic_read(&ops->entries) > ops->gc_thresh * 2;
+       return dst_entries_get_fast(ops) > ops->gc_thresh * 2;
 }
 
 static void xfrm6_update_pmtu(struct dst_entry *dst, u32 mtu)
@@ -255,7 +255,6 @@ static struct dst_ops xfrm6_dst_ops = {
        .ifdown =               xfrm6_dst_ifdown,
        .local_out =            __ip6_local_out,
        .gc_thresh =            1024,
-       .entries =              ATOMIC_INIT(0),
 };
 
 static struct xfrm_policy_afinfo xfrm6_policy_afinfo = {
@@ -312,11 +311,13 @@ int __init xfrm6_init(void)
         */
        gc_thresh = FIB6_TABLE_HASHSZ * 8;
        xfrm6_dst_ops.gc_thresh = (gc_thresh < 1024) ? 1024 : gc_thresh;
+       dst_entries_init(&xfrm6_dst_ops);
 
        ret = xfrm6_policy_init();
-       if (ret)
+       if (ret) {
+               dst_entries_destroy(&xfrm6_dst_ops);
                goto out;
-
+       }
        ret = xfrm6_state_init();
        if (ret)
                goto out_policy;
@@ -341,4 +342,5 @@ void xfrm6_fini(void)
        //xfrm6_input_fini();
        xfrm6_policy_fini();
        xfrm6_state_fini();
+       dst_entries_destroy(&xfrm6_dst_ops);
 }