From c4b2bf6b4a35348fe6d1eb06928eb68d7b9d99a9 Mon Sep 17 00:00:00 2001 From: Tonghao Zhang Date: Mon, 17 Jul 2017 23:28:06 -0700 Subject: openvswitch: Optimize operations for OvS flow_stats. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 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_table.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'net/openvswitch/flow_table.c') 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]); -- cgit v1.2.3