| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-Id: <20220222220450.1154948-1-eric.dumazet@gmail.com>
Date: Tue, 22 Feb 2022 14:04:50 -0800
From: Eric Dumazet <eric.dumazet@...il.com>
To: "David S . Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>
Cc: netdev <netdev@...r.kernel.org>,
Eric Dumazet <edumazet@...gle.com>,
Eric Dumazet <eric.dumazet@...il.com>,
Neil Horman <nhorman@...driver.com>
Subject: [PATCH net-next] drop_monitor: remove quadratic behavior
From: Eric Dumazet <edumazet@...gle.com>
drop_monitor is using an unique list on which all netdevices in
the host have an element, regardless of their netns.
This scales poorly, not only at device unregister time (what I
caught during my netns dismantle stress tests), but also at packet
processing time whenever trace_napi_poll_hit() is called.
If the intent was to avoid adding one pointer in 'struct net_device'
then surely we prefer O(1) behavior.
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Neil Horman <nhorman@...driver.com>
---
include/linux/netdevice.h | 4 +-
net/core/drop_monitor.c | 79 ++++++++++++---------------------------
2 files changed, 27 insertions(+), 56 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 93fc680b658f0f1b31c4d33a34e21b705097ad6f..c79ee22962961810f5f8f2f4529159fd308b8fc6 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2236,7 +2236,9 @@ struct net_device {
#if IS_ENABLED(CONFIG_MRP)
struct mrp_port __rcu *mrp_port;
#endif
-
+#if IS_ENABLED(CONFIG_NET_DROP_MONITOR)
+ struct dm_hw_stat_delta __rcu *dm_private;
+#endif
struct device dev;
const struct attribute_group *sysfs_groups[4];
const struct attribute_group *sysfs_rx_queue_group;
diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
index d7d177f75d43c6fbcdbbf2facaa18c120a541ffb..b89e3e95bffc0f50d477e86959f2bb42af9dce46 100644
--- a/net/core/drop_monitor.c
+++ b/net/core/drop_monitor.c
@@ -64,7 +64,6 @@ static const char * const drop_reasons[] = {
/* net_dm_mutex
*
* An overall lock guarding every operation coming from userspace.
- * It also guards the global 'hw_stats_list' list.
*/
static DEFINE_MUTEX(net_dm_mutex);
@@ -100,11 +99,9 @@ struct per_cpu_dm_data {
};
struct dm_hw_stat_delta {
- struct net_device *dev;
unsigned long last_rx;
- struct list_head list;
- struct rcu_head rcu;
unsigned long last_drop_val;
+ struct rcu_head rcu;
};
static struct genl_family net_drop_monitor_family;
@@ -115,7 +112,6 @@ static DEFINE_PER_CPU(struct per_cpu_dm_data, dm_hw_cpu_data);
static int dm_hit_limit = 64;
static int dm_delay = 1;
static unsigned long dm_hw_check_delta = 2*HZ;
-static LIST_HEAD(hw_stats_list);
static enum net_dm_alert_mode net_dm_alert_mode = NET_DM_ALERT_MODE_SUMMARY;
static u32 net_dm_trunc_len;
@@ -287,33 +283,27 @@ static void trace_kfree_skb_hit(void *ignore, struct sk_buff *skb,
static void trace_napi_poll_hit(void *ignore, struct napi_struct *napi,
int work, int budget)
{
- struct dm_hw_stat_delta *new_stat;
-
+ struct net_device *dev = napi->dev;
+ struct dm_hw_stat_delta *stat;
/*
* Don't check napi structures with no associated device
*/
- if (!napi->dev)
+ if (!dev)
return;
rcu_read_lock();
- list_for_each_entry_rcu(new_stat, &hw_stats_list, list) {
- struct net_device *dev;
-
+ stat = rcu_dereference(dev->dm_private);
+ if (stat) {
/*
* only add a note to our monitor buffer if:
- * 1) this is the dev we received on
- * 2) its after the last_rx delta
- * 3) our rx_dropped count has gone up
+ * 1) its after the last_rx delta
+ * 2) our rx_dropped count has gone up
*/
- /* Paired with WRITE_ONCE() in dropmon_net_event() */
- dev = READ_ONCE(new_stat->dev);
- if ((dev == napi->dev) &&
- (time_after(jiffies, new_stat->last_rx + dm_hw_check_delta)) &&
- (napi->dev->stats.rx_dropped != new_stat->last_drop_val)) {
+ if (time_after(jiffies, stat->last_rx + dm_hw_check_delta) &&
+ (dev->stats.rx_dropped != stat->last_drop_val)) {
trace_drop_common(NULL, NULL);
- new_stat->last_drop_val = napi->dev->stats.rx_dropped;
- new_stat->last_rx = jiffies;
- break;
+ stat->last_drop_val = dev->stats.rx_dropped;
+ stat->last_rx = jiffies;
}
}
rcu_read_unlock();
@@ -1198,7 +1188,6 @@ static int net_dm_trace_on_set(struct netlink_ext_ack *extack)
static void net_dm_trace_off_set(void)
{
- struct dm_hw_stat_delta *new_stat, *temp;
const struct net_dm_alert_ops *ops;
int cpu;
@@ -1222,13 +1211,6 @@ static void net_dm_trace_off_set(void)
consume_skb(skb);
}
- list_for_each_entry_safe(new_stat, temp, &hw_stats_list, list) {
- if (new_stat->dev == NULL) {
- list_del_rcu(&new_stat->list);
- kfree_rcu(new_stat, rcu);
- }
- }
-
module_put(THIS_MODULE);
}
@@ -1589,41 +1571,28 @@ static int dropmon_net_event(struct notifier_block *ev_block,
unsigned long event, void *ptr)
{
struct net_device *dev = netdev_notifier_info_to_dev(ptr);
- struct dm_hw_stat_delta *new_stat = NULL;
- struct dm_hw_stat_delta *tmp;
+ struct dm_hw_stat_delta *stat;
switch (event) {
case NETDEV_REGISTER:
- new_stat = kzalloc(sizeof(struct dm_hw_stat_delta), GFP_KERNEL);
+ if (WARN_ON_ONCE(rtnl_dereference(dev->dm_private)))
+ break;
+ stat = kzalloc(sizeof(*stat), GFP_KERNEL);
+ if (!stat)
+ break;
- if (!new_stat)
- goto out;
+ stat->last_rx = jiffies;
+ rcu_assign_pointer(dev->dm_private, stat);
- new_stat->dev = dev;
- new_stat->last_rx = jiffies;
- mutex_lock(&net_dm_mutex);
- list_add_rcu(&new_stat->list, &hw_stats_list);
- mutex_unlock(&net_dm_mutex);
break;
case NETDEV_UNREGISTER:
- mutex_lock(&net_dm_mutex);
- list_for_each_entry_safe(new_stat, tmp, &hw_stats_list, list) {
- if (new_stat->dev == dev) {
-
- /* Paired with READ_ONCE() in trace_napi_poll_hit() */
- WRITE_ONCE(new_stat->dev, NULL);
-
- if (trace_state == TRACE_OFF) {
- list_del_rcu(&new_stat->list);
- kfree_rcu(new_stat, rcu);
- break;
- }
- }
+ stat = rtnl_dereference(dev->dm_private);
+ if (stat) {
+ rcu_assign_pointer(dev->dm_private, NULL);
+ kfree_rcu(stat, rcu);
}
- mutex_unlock(&net_dm_mutex);
break;
}
-out:
return NOTIFY_DONE;
}
--
2.35.1.473.g83b2b277ed-goog
Powered by blists - more mailing lists