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net dst: use a percpu_counter to track entries

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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>
This commit is contained in:
Eric Dumazet 2010-10-08 06:37:34 +00:00 • committed by David S. Miller
parent 0ed8ddf404
commit fc66f95c68
8 changed files with 100 additions and 35 deletions
Download patch file Download diff file Expand all files Collapse all files

36
net/ipv4/route.c
View 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),