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bonding: initial RCU conversion

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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>
This commit is contained in:
nikolay@redhat.com 2013-08-01 16:54:51 +02:00 committed by David S. Miller
parent 15077228ca
commit 278b208375
5 changed files with 32 additions and 29 deletions
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2
drivers/net/bonding/bond_3ad.c
View File

@ -2426,6 +2426,7 @@ int bond_3ad_xmit_xor(struct sk_buff *skb, struct net_device *dev)
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 @@ int bond_3ad_xmit_xor(struct sk_buff *skb, struct net_device *dev)
}
out:
read_unlock(&bond->lock);
if (res) {
/* no suitable interface, frame not sent */
kfree_skb(skb);

6
drivers/net/bonding/bond_alb.c
View File

@ -1337,6 +1337,7 @@ int bond_alb_xmit(struct sk_buff *skb, struct net_device *bond_dev)
/* 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 @@ int bond_alb_xmit(struct sk_buff *skb, struct net_device *bond_dev)
}
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 @@ void bond_alb_handle_active_change(struct bonding *bond, struct slave *new_slave
}
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;

30
drivers/net/bonding/bond_main.c
View File

@ -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 @@ void bond_change_active_slave(struct bonding *bond, struct slave *new_active)
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 @@ void bond_select_active_slave(struct bonding *bond)
*/
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_attach_slave(struct bonding *bond, struct slave *new_slave)
*/
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 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
* 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 @@ static int __bond_release_one(struct net_device *bond_dev,
}
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 @@ static int __bond_release_one(struct net_device *bond_dev,
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 @@ void bond_xmit_slave_id(struct bonding *bond, struct sk_buff *skb, int slave_id)
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 @@ void bond_xmit_slave_id(struct bonding *bond, struct sk_buff *skb, int slave_id)
/* 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 @@ static int bond_xmit_roundrobin(struct sk_buff *skb, struct net_device *bond_dev
* 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 @@ static int bond_xmit_activebackup(struct sk_buff *skb, struct net_device *bond_d
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 @@ static int bond_xmit_broadcast(struct sk_buff *skb, struct net_device *bond_dev)
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 @@ static inline int bond_slave_override(struct bonding *bond,
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 @@ static netdev_tx_t bond_start_xmit(struct sk_buff *skb, struct net_device *dev)
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;
}

19
drivers/net/bonding/bond_sysfs.c
View File

@ -1243,16 +1243,16 @@ static ssize_t bonding_show_active_slave(struct device *d,
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 @@ static ssize_t bonding_store_active_slave(struct device *d,
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 @@ static ssize_t bonding_show_mii_status(struct device *d,
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);

4
drivers/net/bonding/bonding.h
View File

@ -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