From c4b2bf6b4a35348fe6d1eb06928eb68d7b9d99a9 Mon Sep 17 00:00:00 2001 From: Tonghao Zhang Date: Mon, 17 Jul 2017 23:28:06 -0700 Subject: [PATCH] openvswitch: Optimize operations for OvS flow_stats. MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit When calling the flow_free() to free the flow, we call many times (cpu_possible_mask, eg. 128 as default) cpumask_next(). That will take up our CPU usage if we call the flow_free() frequently. When we put all packets to userspace via upcall, and OvS will send them back via netlink to ovs_packet_cmd_execute(will call flow_free). The test topo is shown as below. VM01 sends TCP packets to VM02, and OvS forward packtets. When testing, we use perf to report the system performance. VM01 --- OvS-VM --- VM02 Without this patch, perf-top show as below: The flow_free() is 3.02% CPU usage. 4.23% [kernel] [k] _raw_spin_unlock_irqrestore 3.62% [kernel] [k] __do_softirq 3.16% [kernel] [k] __memcpy 3.02% [kernel] [k] flow_free 2.42% libc-2.17.so [.] __memcpy_ssse3_back 2.18% [kernel] [k] copy_user_generic_unrolled 2.17% [kernel] [k] find_next_bit When applied this patch, perf-top show as below: Not shown on the list anymore. 4.11% [kernel] [k] _raw_spin_unlock_irqrestore 3.79% [kernel] [k] __do_softirq 3.46% [kernel] [k] __memcpy 2.73% libc-2.17.so [.] __memcpy_ssse3_back 2.25% [kernel] [k] copy_user_generic_unrolled 1.89% libc-2.17.so [.] _int_malloc 1.53% ovs-vswitchd [.] xlate_actions With this patch, the TCP throughput(we dont use Megaflow Cache + Microflow Cache) between VMs is 1.18Gbs/sec up to 1.30Gbs/sec (maybe ~10% performance imporve). This patch adds cpumask struct, the cpu_used_mask stores the cpu_id that the flow used. And we only check the flow_stats on the cpu we used, and it is unncessary to check all possible cpu when getting, cleaning, and updating the flow_stats. Adding the cpu_used_mask to sw_flow struct does’t increase the cacheline number. Signed-off-by: Tonghao Zhang Acked-by: Pravin B Shelar Signed-off-by: David S. Miller --- net/openvswitch/flow.c | 7 ++++--- net/openvswitch/flow.h | 2 ++ net/openvswitch/flow_table.c | 4 +++- 3 files changed, 9 insertions(+), 4 deletions(-) diff --git a/net/openvswitch/flow.c b/net/openvswitch/flow.c index 6ef51e764367..8c94cef25a72 100644 --- a/net/openvswitch/flow.c +++ b/net/openvswitch/flow.c @@ -72,7 +72,7 @@ void ovs_flow_stats_update(struct sw_flow *flow, __be16 tcp_flags, const struct sk_buff *skb) { struct flow_stats *stats; - int cpu = smp_processor_id(); + unsigned int cpu = smp_processor_id(); int len = skb->len + (skb_vlan_tag_present(skb) ? VLAN_HLEN : 0); stats = rcu_dereference(flow->stats[cpu]); @@ -117,6 +117,7 @@ void ovs_flow_stats_update(struct sw_flow *flow, __be16 tcp_flags, rcu_assign_pointer(flow->stats[cpu], new_stats); + cpumask_set_cpu(cpu, &flow->cpu_used_mask); goto unlock; } } @@ -144,7 +145,7 @@ void ovs_flow_stats_get(const struct sw_flow *flow, memset(ovs_stats, 0, sizeof(*ovs_stats)); /* We open code this to make sure cpu 0 is always considered */ - for (cpu = 0; cpu < nr_cpu_ids; cpu = cpumask_next(cpu, cpu_possible_mask)) { + for (cpu = 0; cpu < nr_cpu_ids; cpu = cpumask_next(cpu, &flow->cpu_used_mask)) { struct flow_stats *stats = rcu_dereference_ovsl(flow->stats[cpu]); if (stats) { @@ -168,7 +169,7 @@ void ovs_flow_stats_clear(struct sw_flow *flow) int cpu; /* We open code this to make sure cpu 0 is always considered */ - for (cpu = 0; cpu < nr_cpu_ids; cpu = cpumask_next(cpu, cpu_possible_mask)) { + for (cpu = 0; cpu < nr_cpu_ids; cpu = cpumask_next(cpu, &flow->cpu_used_mask)) { struct flow_stats *stats = ovsl_dereference(flow->stats[cpu]); if (stats) { diff --git a/net/openvswitch/flow.h b/net/openvswitch/flow.h index a9bc1c875965..1875bba4f865 100644 --- a/net/openvswitch/flow.h +++ b/net/openvswitch/flow.h @@ -31,6 +31,7 @@ #include #include #include +#include #include #include #include @@ -219,6 +220,7 @@ struct sw_flow { */ struct sw_flow_key key; struct sw_flow_id id; + struct cpumask cpu_used_mask; struct sw_flow_mask *mask; struct sw_flow_actions __rcu *sf_acts; struct flow_stats __rcu *stats[]; /* One for each CPU. First one diff --git a/net/openvswitch/flow_table.c b/net/openvswitch/flow_table.c index ea7a8073fa02..80ea2a71852e 100644 --- a/net/openvswitch/flow_table.c +++ b/net/openvswitch/flow_table.c @@ -98,6 +98,8 @@ struct sw_flow *ovs_flow_alloc(void) RCU_INIT_POINTER(flow->stats[0], stats); + cpumask_set_cpu(0, &flow->cpu_used_mask); + return flow; err: kmem_cache_free(flow_cache, flow); @@ -141,7 +143,7 @@ static void flow_free(struct sw_flow *flow) if (flow->sf_acts) ovs_nla_free_flow_actions((struct sw_flow_actions __force *)flow->sf_acts); /* We open code this to make sure cpu 0 is always considered */ - for (cpu = 0; cpu < nr_cpu_ids; cpu = cpumask_next(cpu, cpu_possible_mask)) + for (cpu = 0; cpu < nr_cpu_ids; cpu = cpumask_next(cpu, &flow->cpu_used_mask)) if (flow->stats[cpu]) kmem_cache_free(flow_stats_cache, (struct flow_stats __force *)flow->stats[cpu]); -- 2.20.1