[IPV4] route cache: Introduce rt_genid for smooth cache invalidation
Current ip route cache implementation is not suited to large caches.
We can consume a lot of CPU when cache must be invalidated, since we
currently need to evict all cache entries, and this eviction is
sometimes asynchronous. min_delay & max_delay can somewhat control this
asynchronism behavior, but whole thing is a kludge, regularly triggering
infamous soft lockup messages. When entries are still in use, this also
consumes a lot of ram, filling dst_garbage.list.
A better scheme is to use a generation identifier on each entry,
so that cache invalidation can be performed by changing the table
identifier, without having to scan all entries.
No more delayed flushing, no more stalling when secret_interval expires.
Invalidated entries will then be freed at GC time (controled by
ip_rt_gc_timeout or stress), or when an invalidated entry is found
in a chain when an insert is done.
Thus we keep a normal equilibrium.
This patch :
- renames rt_hash_rnd to rt_genid (and makes it an atomic_t)
- Adds a new rt_genid field to 'struct rtable' (filling a hole on 64bit)
- Checks entry->rt_genid at appropriate places :
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 163086b..8842ecb 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -117,8 +117,6 @@
#define RT_GC_TIMEOUT (300*HZ)
-static int ip_rt_min_delay = 2 * HZ;
-static int ip_rt_max_delay = 10 * HZ;
static int ip_rt_max_size;
static int ip_rt_gc_timeout = RT_GC_TIMEOUT;
static int ip_rt_gc_interval = 60 * HZ;
@@ -133,12 +131,9 @@
static int ip_rt_min_pmtu = 512 + 20 + 20;
static int ip_rt_min_advmss = 256;
static int ip_rt_secret_interval = 10 * 60 * HZ;
-static int ip_rt_flush_expected;
-static unsigned long rt_deadline;
#define RTprint(a...) printk(KERN_DEBUG a)
-static struct timer_list rt_flush_timer;
static void rt_worker_func(struct work_struct *work);
static DECLARE_DELAYED_WORK(expires_work, rt_worker_func);
static struct timer_list rt_secret_timer;
@@ -260,19 +255,16 @@
static struct rt_hash_bucket *rt_hash_table;
static unsigned rt_hash_mask;
static unsigned int rt_hash_log;
-static unsigned int rt_hash_rnd;
+static atomic_t rt_genid;
static DEFINE_PER_CPU(struct rt_cache_stat, rt_cache_stat);
#define RT_CACHE_STAT_INC(field) \
(__raw_get_cpu_var(rt_cache_stat).field++)
-static int rt_intern_hash(unsigned hash, struct rtable *rth,
- struct rtable **res);
-
static unsigned int rt_hash_code(u32 daddr, u32 saddr)
{
- return (jhash_2words(daddr, saddr, rt_hash_rnd)
- & rt_hash_mask);
+ return jhash_2words(daddr, saddr, atomic_read(&rt_genid))
+ & rt_hash_mask;
}
#define rt_hash(daddr, saddr, idx) \
@@ -282,27 +274,28 @@
#ifdef CONFIG_PROC_FS
struct rt_cache_iter_state {
int bucket;
+ int genid;
};
-static struct rtable *rt_cache_get_first(struct seq_file *seq)
+static struct rtable *rt_cache_get_first(struct rt_cache_iter_state *st)
{
struct rtable *r = NULL;
- struct rt_cache_iter_state *st = seq->private;
for (st->bucket = rt_hash_mask; st->bucket >= 0; --st->bucket) {
rcu_read_lock_bh();
- r = rt_hash_table[st->bucket].chain;
- if (r)
- break;
+ r = rcu_dereference(rt_hash_table[st->bucket].chain);
+ while (r) {
+ if (r->rt_genid == st->genid)
+ return r;
+ r = rcu_dereference(r->u.dst.rt_next);
+ }
rcu_read_unlock_bh();
}
- return rcu_dereference(r);
+ return r;
}
-static struct rtable *rt_cache_get_next(struct seq_file *seq, struct rtable *r)
+static struct rtable *rt_cache_get_next(struct rt_cache_iter_state *st, struct rtable *r)
{
- struct rt_cache_iter_state *st = seq->private;
-
r = r->u.dst.rt_next;
while (!r) {
rcu_read_unlock_bh();
@@ -314,29 +307,38 @@
return rcu_dereference(r);
}
-static struct rtable *rt_cache_get_idx(struct seq_file *seq, loff_t pos)
+static struct rtable *rt_cache_get_idx(struct rt_cache_iter_state *st, loff_t pos)
{
- struct rtable *r = rt_cache_get_first(seq);
+ struct rtable *r = rt_cache_get_first(st);
if (r)
- while (pos && (r = rt_cache_get_next(seq, r)))
+ while (pos && (r = rt_cache_get_next(st, r))) {
+ if (r->rt_genid != st->genid)
+ continue;
--pos;
+ }
return pos ? NULL : r;
}
static void *rt_cache_seq_start(struct seq_file *seq, loff_t *pos)
{
- return *pos ? rt_cache_get_idx(seq, *pos - 1) : SEQ_START_TOKEN;
+ struct rt_cache_iter_state *st = seq->private;
+
+ if (*pos)
+ return rt_cache_get_idx(st, *pos - 1);
+ st->genid = atomic_read(&rt_genid);
+ return SEQ_START_TOKEN;
}
static void *rt_cache_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
- struct rtable *r = NULL;
+ struct rtable *r;
+ struct rt_cache_iter_state *st = seq->private;
if (v == SEQ_START_TOKEN)
- r = rt_cache_get_first(seq);
+ r = rt_cache_get_first(st);
else
- r = rt_cache_get_next(seq, v);
+ r = rt_cache_get_next(st, v);
++*pos;
return r;
}
@@ -709,6 +711,11 @@
continue;
spin_lock_bh(rt_hash_lock_addr(i));
while ((rth = *rthp) != NULL) {
+ if (rth->rt_genid != atomic_read(&rt_genid)) {
+ *rthp = rth->u.dst.rt_next;
+ rt_free(rth);
+ continue;
+ }
if (rth->u.dst.expires) {
/* Entry is expired even if it is in use */
if (time_before_eq(jiffies, rth->u.dst.expires)) {
@@ -733,83 +740,45 @@
/*
* rt_worker_func() is run in process context.
- * If a whole flush was scheduled, it is done.
- * Else, we call rt_check_expire() to scan part of the hash table
+ * we call rt_check_expire() to scan part of the hash table
*/
static void rt_worker_func(struct work_struct *work)
{
- if (ip_rt_flush_expected) {
- ip_rt_flush_expected = 0;
- rt_do_flush(1);
- } else
- rt_check_expire();
+ rt_check_expire();
schedule_delayed_work(&expires_work, ip_rt_gc_interval);
}
-/* This can run from both BH and non-BH contexts, the latter
- * in the case of a forced flush event.
+/*
+ * Pertubation of rt_genid by a small quantity [1..256]
+ * Using 8 bits of shuffling ensure we can call rt_cache_invalidate()
+ * many times (2^24) without giving recent rt_genid.
+ * Jenkins hash is strong enough that litle changes of rt_genid are OK.
*/
-static void rt_run_flush(unsigned long process_context)
+static void rt_cache_invalidate(void)
{
- rt_deadline = 0;
+ unsigned char shuffle;
- get_random_bytes(&rt_hash_rnd, 4);
-
- rt_do_flush(process_context);
-}
-
-static DEFINE_SPINLOCK(rt_flush_lock);
-
-void rt_cache_flush(int delay)
-{
- unsigned long now = jiffies;
- int user_mode = !in_softirq();
-
- if (delay < 0)
- delay = ip_rt_min_delay;
-
- spin_lock_bh(&rt_flush_lock);
-
- if (del_timer(&rt_flush_timer) && delay > 0 && rt_deadline) {
- long tmo = (long)(rt_deadline - now);
-
- /* If flush timer is already running
- and flush request is not immediate (delay > 0):
-
- if deadline is not achieved, prolongate timer to "delay",
- otherwise fire it at deadline time.
- */
-
- if (user_mode && tmo < ip_rt_max_delay-ip_rt_min_delay)
- tmo = 0;
-
- if (delay > tmo)
- delay = tmo;
- }
-
- if (delay <= 0) {
- spin_unlock_bh(&rt_flush_lock);
- rt_run_flush(user_mode);
- return;
- }
-
- if (rt_deadline == 0)
- rt_deadline = now + ip_rt_max_delay;
-
- mod_timer(&rt_flush_timer, now+delay);
- spin_unlock_bh(&rt_flush_lock);
+ get_random_bytes(&shuffle, sizeof(shuffle));
+ atomic_add(shuffle + 1U, &rt_genid);
}
/*
- * We change rt_hash_rnd and ask next rt_worker_func() invocation
- * to perform a flush in process context
+ * delay < 0 : invalidate cache (fast : entries will be deleted later)
+ * delay >= 0 : invalidate & flush cache (can be long)
+ */
+void rt_cache_flush(int delay)
+{
+ rt_cache_invalidate();
+ if (delay >= 0)
+ rt_do_flush(!in_softirq());
+}
+
+/*
+ * We change rt_genid and let gc do the cleanup
*/
static void rt_secret_rebuild(unsigned long dummy)
{
- get_random_bytes(&rt_hash_rnd, 4);
- ip_rt_flush_expected = 1;
- cancel_delayed_work(&expires_work);
- schedule_delayed_work(&expires_work, HZ/10);
+ rt_cache_invalidate();
mod_timer(&rt_secret_timer, jiffies + ip_rt_secret_interval);
}
@@ -886,7 +855,8 @@
rthp = &rt_hash_table[k].chain;
spin_lock_bh(rt_hash_lock_addr(k));
while ((rth = *rthp) != NULL) {
- if (!rt_may_expire(rth, tmo, expire)) {
+ if (rth->rt_genid == atomic_read(&rt_genid) &&
+ !rt_may_expire(rth, tmo, expire)) {
tmo >>= 1;
rthp = &rth->u.dst.rt_next;
continue;
@@ -967,6 +937,11 @@
spin_lock_bh(rt_hash_lock_addr(hash));
while ((rth = *rthp) != NULL) {
+ if (rth->rt_genid != atomic_read(&rt_genid)) {
+ *rthp = rth->u.dst.rt_next;
+ rt_free(rth);
+ continue;
+ }
if (compare_keys(&rth->fl, &rt->fl) && compare_netns(rth, rt)) {
/* Put it first */
*rthp = rth->u.dst.rt_next;
@@ -1132,17 +1107,19 @@
static void rt_del(unsigned hash, struct rtable *rt)
{
- struct rtable **rthp;
+ struct rtable **rthp, *aux;
+ rthp = &rt_hash_table[hash].chain;
spin_lock_bh(rt_hash_lock_addr(hash));
ip_rt_put(rt);
- for (rthp = &rt_hash_table[hash].chain; *rthp;
- rthp = &(*rthp)->u.dst.rt_next)
- if (*rthp == rt) {
- *rthp = rt->u.dst.rt_next;
- rt_free(rt);
- break;
+ while ((aux = *rthp) != NULL) {
+ if (aux == rt || (aux->rt_genid != atomic_read(&rt_genid))) {
+ *rthp = aux->u.dst.rt_next;
+ rt_free(aux);
+ continue;
}
+ rthp = &aux->u.dst.rt_next;
+ }
spin_unlock_bh(rt_hash_lock_addr(hash));
}
@@ -1187,7 +1164,8 @@
if (rth->fl.fl4_dst != daddr ||
rth->fl.fl4_src != skeys[i] ||
rth->fl.oif != ikeys[k] ||
- rth->fl.iif != 0) {
+ rth->fl.iif != 0 ||
+ rth->rt_genid != atomic_read(&rt_genid)) {
rthp = &rth->u.dst.rt_next;
continue;
}
@@ -1225,7 +1203,7 @@
rt->u.dst.neighbour = NULL;
rt->u.dst.hh = NULL;
rt->u.dst.xfrm = NULL;
-
+ rt->rt_genid = atomic_read(&rt_genid);
rt->rt_flags |= RTCF_REDIRECTED;
/* Gateway is different ... */
@@ -1446,7 +1424,8 @@
rth->rt_src == iph->saddr &&
rth->fl.iif == 0 &&
!(dst_metric_locked(&rth->u.dst, RTAX_MTU)) &&
- rth->u.dst.dev->nd_net == net) {
+ rth->u.dst.dev->nd_net == net &&
+ rth->rt_genid == atomic_read(&rt_genid)) {
unsigned short mtu = new_mtu;
if (new_mtu < 68 || new_mtu >= old_mtu) {
@@ -1681,8 +1660,9 @@
rth->fl.oif = 0;
rth->rt_gateway = daddr;
rth->rt_spec_dst= spec_dst;
- rth->rt_type = RTN_MULTICAST;
+ rth->rt_genid = atomic_read(&rt_genid);
rth->rt_flags = RTCF_MULTICAST;
+ rth->rt_type = RTN_MULTICAST;
if (our) {
rth->u.dst.input= ip_local_deliver;
rth->rt_flags |= RTCF_LOCAL;
@@ -1821,6 +1801,7 @@
rth->u.dst.input = ip_forward;
rth->u.dst.output = ip_output;
+ rth->rt_genid = atomic_read(&rt_genid);
rt_set_nexthop(rth, res, itag);
@@ -1981,6 +1962,7 @@
goto e_nobufs;
rth->u.dst.output= ip_rt_bug;
+ rth->rt_genid = atomic_read(&rt_genid);
atomic_set(&rth->u.dst.__refcnt, 1);
rth->u.dst.flags= DST_HOST;
@@ -2072,7 +2054,8 @@
rth->fl.oif == 0 &&
rth->fl.mark == skb->mark &&
rth->fl.fl4_tos == tos &&
- rth->u.dst.dev->nd_net == net) {
+ rth->u.dst.dev->nd_net == net &&
+ rth->rt_genid == atomic_read(&rt_genid)) {
dst_use(&rth->u.dst, jiffies);
RT_CACHE_STAT_INC(in_hit);
rcu_read_unlock();
@@ -2200,6 +2183,7 @@
rth->rt_spec_dst= fl->fl4_src;
rth->u.dst.output=ip_output;
+ rth->rt_genid = atomic_read(&rt_genid);
RT_CACHE_STAT_INC(out_slow_tot);
@@ -2472,7 +2456,8 @@
rth->fl.mark == flp->mark &&
!((rth->fl.fl4_tos ^ flp->fl4_tos) &
(IPTOS_RT_MASK | RTO_ONLINK)) &&
- rth->u.dst.dev->nd_net == net) {
+ rth->u.dst.dev->nd_net == net &&
+ rth->rt_genid == atomic_read(&rt_genid)) {
dst_use(&rth->u.dst, jiffies);
RT_CACHE_STAT_INC(out_hit);
rcu_read_unlock_bh();
@@ -2527,6 +2512,7 @@
rt->idev = ort->idev;
if (rt->idev)
in_dev_hold(rt->idev);
+ rt->rt_genid = atomic_read(&rt_genid);
rt->rt_flags = ort->rt_flags;
rt->rt_type = ort->rt_type;
rt->rt_dst = ort->rt_dst;
@@ -2781,6 +2767,8 @@
rt = rcu_dereference(rt->u.dst.rt_next), idx++) {
if (idx < s_idx)
continue;
+ if (rt->rt_genid != atomic_read(&rt_genid))
+ continue;
skb->dst = dst_clone(&rt->u.dst);
if (rt_fill_info(skb, NETLINK_CB(cb->skb).pid,
cb->nlh->nlmsg_seq, RTM_NEWROUTE,
@@ -2850,24 +2838,6 @@
.strategy = &ipv4_sysctl_rtcache_flush_strategy,
},
{
- .ctl_name = NET_IPV4_ROUTE_MIN_DELAY,
- .procname = "min_delay",
- .data = &ip_rt_min_delay,
- .maxlen = sizeof(int),
- .mode = 0644,
- .proc_handler = &proc_dointvec_jiffies,
- .strategy = &sysctl_jiffies,
- },
- {
- .ctl_name = NET_IPV4_ROUTE_MAX_DELAY,
- .procname = "max_delay",
- .data = &ip_rt_max_delay,
- .maxlen = sizeof(int),
- .mode = 0644,
- .proc_handler = &proc_dointvec_jiffies,
- .strategy = &sysctl_jiffies,
- },
- {
.ctl_name = NET_IPV4_ROUTE_GC_THRESH,
.procname = "gc_thresh",
.data = &ipv4_dst_ops.gc_thresh,
@@ -3025,8 +2995,8 @@
{
int rc = 0;
- rt_hash_rnd = (int) ((num_physpages ^ (num_physpages>>8)) ^
- (jiffies ^ (jiffies >> 7)));
+ atomic_set(&rt_genid, (int) ((num_physpages ^ (num_physpages>>8)) ^
+ (jiffies ^ (jiffies >> 7))));
#ifdef CONFIG_NET_CLS_ROUTE
ip_rt_acct = __alloc_percpu(256 * sizeof(struct ip_rt_acct));
@@ -3059,7 +3029,6 @@
devinet_init();
ip_fib_init();
- setup_timer(&rt_flush_timer, rt_run_flush, 0);
setup_timer(&rt_secret_timer, rt_secret_rebuild, 0);
/* All the timers, started at system startup tend
