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Message-Id: <1500272964-27238-2-git-send-email-xiangxia.m.yue@gmail.com>
Date: Sun, 16 Jul 2017 23:29:24 -0700
From: Tonghao Zhang <xiangxia.m.yue@...il.com>
To: netdev@...r.kernel.org
Cc: pshelar@....org, dev@...nvswitch.org,
Tonghao Zhang <xiangxia.m.yue@...il.com>
Subject: [PATCH 2/2] openvswitch: Optimize operations for OvS flow_stats.
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 <xiangxia.m.yue@...il.com>
---
net/openvswitch/flow.c | 7 ++++---
net/openvswitch/flow.h | 2 ++
net/openvswitch/flow_table.c | 5 ++++-
3 files changed, 10 insertions(+), 4 deletions(-)
diff --git a/net/openvswitch/flow.c b/net/openvswitch/flow.c
index 89aeb32..cfb652a 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 a9bc1c8..1875bba 100644
--- a/net/openvswitch/flow.h
+++ b/net/openvswitch/flow.h
@@ -31,6 +31,7 @@
#include <linux/jiffies.h>
#include <linux/time.h>
#include <linux/flex_array.h>
+#include <linux/cpumask.h>
#include <net/inet_ecn.h>
#include <net/ip_tunnels.h>
#include <net/dst_metadata.h>
@@ -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 ea7a807..324a246 100644
--- a/net/openvswitch/flow_table.c
+++ b/net/openvswitch/flow_table.c
@@ -98,6 +98,9 @@ struct sw_flow *ovs_flow_alloc(void)
RCU_INIT_POINTER(flow->stats[0], stats);
+ cpumask_clear(&flow->cpu_used_mask);
+ cpumask_set_cpu(0, &flow->cpu_used_mask);
+
return flow;
err:
kmem_cache_free(flow_cache, flow);
@@ -141,7 +144,7 @@ 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]);
--
1.8.3.1
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