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net: bonding: Use per-cpu rr_tx_counter

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The round-robin rr_tx_counter was shared across CPUs leading to
significant cache thrashing at high packet rates. This patch switches
the round-robin packet counter to use a per-cpu variable to decide
the destination slave.

On a test with 2x100Gbit ICE nic with pktgen_sample_04_many_flows.sh
(-s 64 -t 32) the tx rate was 19.6Mpps before and 22.3Mpps after
this patch.

"perf top -e cache_misses" before:
    12.31%  [bonding]       [k] bond_xmit_roundrobin_slave_get
    10.59%  [sch_fq_codel]  [k] fq_codel_dequeue
     9.34%  [kernel]        [k] skb_release_data
after:
    15.42%  [sch_fq_codel]  [k] fq_codel_dequeue
    10.06%  [kernel]        [k] __memset
     9.12%  [kernel]        [k] skb_release_data

Signed-off-by: Jussi Maki <joamaki@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jussi Maki 2021-06-15 08:54:15 +00:00 committed by David S. Miller
parent b8f6b0522c
commit 848ca9182a
2 changed files with 16 additions and 4 deletions
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18
drivers/net/bonding/bond_main.c
View file

@ -4202,16 +4202,16 @@ static u32 bond_rr_gen_slave_id(struct bonding *bond)
slave_id = prandom_u32();
break;
case 1:
slave_id = bond->rr_tx_counter;
slave_id = this_cpu_inc_return(*bond->rr_tx_counter);
break;
default:
reciprocal_packets_per_slave =
bond->params.reciprocal_packets_per_slave;
slave_id = reciprocal_divide(bond->rr_tx_counter,
slave_id = this_cpu_inc_return(*bond->rr_tx_counter);
slave_id = reciprocal_divide(slave_id,
reciprocal_packets_per_slave);
break;
}
bond->rr_tx_counter++;
return slave_id;
}
@ -4852,6 +4852,9 @@ static void bond_destructor(struct net_device *bond_dev)
if (bond->wq)
destroy_workqueue(bond->wq);
if (bond->rr_tx_counter)
free_percpu(bond->rr_tx_counter);
}
void bond_setup(struct net_device *bond_dev)
@ -5350,6 +5353,15 @@ static int bond_init(struct net_device *bond_dev)
if (!bond->wq)
return -ENOMEM;
if (BOND_MODE(bond) == BOND_MODE_ROUNDROBIN) {
bond->rr_tx_counter = alloc_percpu(u32);
if (!bond->rr_tx_counter) {
destroy_workqueue(bond->wq);
bond->wq = NULL;
return -ENOMEM;
}
}
spin_lock_init(&bond->stats_lock);
netdev_lockdep_set_classes(bond_dev);

2
include/net/bonding.h
View file

@ -232,7 +232,7 @@ struct bonding {
char proc_file_name[IFNAMSIZ];
#endif /* CONFIG_PROC_FS */
struct list_head bond_list;
u32 rr_tx_counter;
u32 __percpu *rr_tx_counter;
struct ad_bond_info ad_info;
struct alb_bond_info alb_info;
struct bond_params params;