bonding: initial RCU conversion
This patch does the initial bonding conversion to RCU. After it the
following modes are protected by RCU alone: roundrobin, active-backup,
broadcast and xor. Modes ALB/TLB and 3ad still acquire bond->lock for
reading, and will be dealt with later. curr_active_slave needs to be
dereferenced via rcu in the converted modes because the only thing
protecting the slave after this patch is rcu_read_lock, so we need the
proper barrier for weakly ordered archs and to make sure we don't have
stale pointer. It's not tagged with __rcu yet because there's still work
to be done to remove the curr_slave_lock, so sparse will complain when
rcu_assign_pointer and rcu_dereference are used, but the alternative to use
rcu_dereference_protected would've created much bigger code churn which is
more difficult to test and review. That will be converted in time.
1. Active-backup mode
1.1 Perf recording while doing iperf -P 4
- old bonding: iperf spent 0.55% in bonding, system spent 0.29% CPU
in bonding
- new bonding: iperf spent 0.29% in bonding, system spent 0.15% CPU
in bonding
1.2. Bandwidth measurements
- old bonding: 16.1 gbps consistently
- new bonding: 17.5 gbps consistently
2. Round-robin mode
2.1 Perf recording while doing iperf -P 4
- old bonding: iperf spent 0.51% in bonding, system spent 0.24% CPU
in bonding
- new bonding: iperf spent 0.16% in bonding, system spent 0.11% CPU
in bonding
2.2 Bandwidth measurements
- old bonding: 8 gbps (variable due to packet reorderings)
- new bonding: 10 gbps (variable due to packet reorderings)
Of course the latency has improved in all converted modes, and moreover
while
doing enslave/release (since it doesn't affect tx anymore).
Also I've stress tested all modes doing enslave/release in a loop while
transmitting traffic.
Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c
index 7d46fa8..9010265 100644
--- a/drivers/net/bonding/bond_3ad.c
+++ b/drivers/net/bonding/bond_3ad.c
@@ -2426,6 +2426,7 @@
struct ad_info ad_info;
int res = 1;
+ read_lock(&bond->lock);
if (__bond_3ad_get_active_agg_info(bond, &ad_info)) {
pr_debug("%s: Error: __bond_3ad_get_active_agg_info failed\n",
dev->name);
@@ -2475,6 +2476,7 @@
}
out:
+ read_unlock(&bond->lock);
if (res) {
/* no suitable interface, frame not sent */
kfree_skb(skb);
diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
index 4d35196..3a5db7b 100644
--- a/drivers/net/bonding/bond_alb.c
+++ b/drivers/net/bonding/bond_alb.c
@@ -1337,6 +1337,7 @@
/* make sure that the curr_active_slave do not change during tx
*/
+ read_lock(&bond->lock);
read_lock(&bond->curr_slave_lock);
switch (ntohs(skb->protocol)) {
@@ -1441,11 +1442,12 @@
}
read_unlock(&bond->curr_slave_lock);
-
+ read_unlock(&bond->lock);
if (res) {
/* no suitable interface, frame not sent */
kfree_skb(skb);
}
+
return NETDEV_TX_OK;
}
@@ -1663,7 +1665,7 @@
}
swap_slave = bond->curr_active_slave;
- bond->curr_active_slave = new_slave;
+ rcu_assign_pointer(bond->curr_active_slave, new_slave);
if (!new_slave || list_empty(&bond->slave_list))
return;
diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 5eee95c..1d37a96 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -77,6 +77,7 @@
#include <net/net_namespace.h>
#include <net/netns/generic.h>
#include <net/pkt_sched.h>
+#include <linux/rculist.h>
#include "bonding.h"
#include "bond_3ad.h"
#include "bond_alb.h"
@@ -1037,7 +1038,7 @@
if (new_active)
bond_set_slave_active_flags(new_active);
} else {
- bond->curr_active_slave = new_active;
+ rcu_assign_pointer(bond->curr_active_slave, new_active);
}
if (bond->params.mode == BOND_MODE_ACTIVEBACKUP) {
@@ -1127,7 +1128,7 @@
*/
static void bond_attach_slave(struct bonding *bond, struct slave *new_slave)
{
- list_add_tail(&new_slave->list, &bond->slave_list);
+ list_add_tail_rcu(&new_slave->list, &bond->slave_list);
bond->slave_cnt++;
}
@@ -1143,7 +1144,7 @@
*/
static void bond_detach_slave(struct bonding *bond, struct slave *slave)
{
- list_del(&slave->list);
+ list_del_rcu(&slave->list);
bond->slave_cnt--;
}
@@ -1751,7 +1752,7 @@
* so we can change it without calling change_active_interface()
*/
if (!bond->curr_active_slave && new_slave->link == BOND_LINK_UP)
- bond->curr_active_slave = new_slave;
+ rcu_assign_pointer(bond->curr_active_slave, new_slave);
break;
} /* switch(bond_mode) */
@@ -1951,7 +1952,7 @@
}
if (all) {
- bond->curr_active_slave = NULL;
+ rcu_assign_pointer(bond->curr_active_slave, NULL);
} else if (oldcurrent == slave) {
/*
* Note that we hold RTNL over this sequence, so there
@@ -1983,6 +1984,7 @@
write_unlock_bh(&bond->lock);
unblock_netpoll_tx();
+ synchronize_rcu();
if (list_empty(&bond->slave_list)) {
call_netdevice_notifiers(NETDEV_CHANGEADDR, bond->dev);
@@ -3811,7 +3813,7 @@
int i = slave_id;
/* Here we start from the slave with slave_id */
- bond_for_each_slave(bond, slave) {
+ bond_for_each_slave_rcu(bond, slave) {
if (--i < 0) {
if (slave_can_tx(slave)) {
bond_dev_queue_xmit(bond, skb, slave->dev);
@@ -3822,7 +3824,7 @@
/* Here we start from the first slave up to slave_id */
i = slave_id;
- bond_for_each_slave(bond, slave) {
+ bond_for_each_slave_rcu(bond, slave) {
if (--i < 0)
break;
if (slave_can_tx(slave)) {
@@ -3848,7 +3850,7 @@
* will send all of this type of traffic.
*/
if (iph->protocol == IPPROTO_IGMP && skb->protocol == htons(ETH_P_IP)) {
- slave = bond->curr_active_slave;
+ slave = rcu_dereference(bond->curr_active_slave);
if (slave && slave_can_tx(slave))
bond_dev_queue_xmit(bond, skb, slave->dev);
else
@@ -3870,7 +3872,7 @@
struct bonding *bond = netdev_priv(bond_dev);
struct slave *slave;
- slave = bond->curr_active_slave;
+ slave = rcu_dereference(bond->curr_active_slave);
if (slave)
bond_dev_queue_xmit(bond, skb, slave->dev);
else
@@ -3900,7 +3902,7 @@
struct bonding *bond = netdev_priv(bond_dev);
struct slave *slave = NULL;
- bond_for_each_slave(bond, slave) {
+ bond_for_each_slave_rcu(bond, slave) {
if (bond_is_last_slave(bond, slave))
break;
if (IS_UP(slave->dev) && slave->link == BOND_LINK_UP) {
@@ -3955,7 +3957,7 @@
return 1;
/* Find out if any slaves have the same mapping as this skb. */
- bond_for_each_slave(bond, check_slave) {
+ bond_for_each_slave_rcu(bond, check_slave) {
if (check_slave->queue_id == skb->queue_mapping) {
slave = check_slave;
break;
@@ -4040,14 +4042,12 @@
if (is_netpoll_tx_blocked(dev))
return NETDEV_TX_BUSY;
- read_lock(&bond->lock);
-
+ rcu_read_lock();
if (!list_empty(&bond->slave_list))
ret = __bond_start_xmit(skb, dev);
else
kfree_skb(skb);
-
- read_unlock(&bond->lock);
+ rcu_read_unlock();
return ret;
}
diff --git a/drivers/net/bonding/bond_sysfs.c b/drivers/net/bonding/bond_sysfs.c
index 0702e91..0f539de 100644
--- a/drivers/net/bonding/bond_sysfs.c
+++ b/drivers/net/bonding/bond_sysfs.c
@@ -1243,16 +1243,16 @@
struct device_attribute *attr,
char *buf)
{
- struct slave *curr;
struct bonding *bond = to_bond(d);
+ struct slave *curr;
int count = 0;
- read_lock(&bond->curr_slave_lock);
- curr = bond->curr_active_slave;
- read_unlock(&bond->curr_slave_lock);
-
+ rcu_read_lock();
+ curr = rcu_dereference(bond->curr_active_slave);
if (USES_PRIMARY(bond->params.mode) && curr)
count = sprintf(buf, "%s\n", curr->dev->name);
+ rcu_read_unlock();
+
return count;
}
@@ -1284,7 +1284,7 @@
if (!strlen(ifname) || buf[0] == '\n') {
pr_info("%s: Clearing current active slave.\n",
bond->dev->name);
- bond->curr_active_slave = NULL;
+ rcu_assign_pointer(bond->curr_active_slave, NULL);
bond_select_active_slave(bond);
goto out;
}
@@ -1347,14 +1347,9 @@
struct device_attribute *attr,
char *buf)
{
- struct slave *curr;
struct bonding *bond = to_bond(d);
- read_lock(&bond->curr_slave_lock);
- curr = bond->curr_active_slave;
- read_unlock(&bond->curr_slave_lock);
-
- return sprintf(buf, "%s\n", curr ? "up" : "down");
+ return sprintf(buf, "%s\n", bond->curr_active_slave ? "up" : "down");
}
static DEVICE_ATTR(mii_status, S_IRUGO, bonding_show_mii_status, NULL);
diff --git a/drivers/net/bonding/bonding.h b/drivers/net/bonding/bonding.h
index 0995974..4bf52d5 100644
--- a/drivers/net/bonding/bonding.h
+++ b/drivers/net/bonding/bonding.h
@@ -116,6 +116,10 @@
#define bond_for_each_slave(bond, pos) \
list_for_each_entry(pos, &(bond)->slave_list, list)
+/* Caller must have rcu_read_lock */
+#define bond_for_each_slave_rcu(bond, pos) \
+ list_for_each_entry_rcu(pos, &(bond)->slave_list, list)
+
/**
* bond_for_each_slave_reverse - iterate in reverse from a given position
* @bond: the bond holding this list