Commit 15ea59a0 authored by Eddy Tao's avatar Eddy Tao Committed by Jakub Kicinski
Browse files

net: openvswitch: reduce cpu_used_mask memory 



Use actual CPU number instead of hardcoded value to decide the size
of 'cpu_used_mask' in 'struct sw_flow'. Below is the reason.

'struct cpumask cpu_used_mask' is embedded in struct sw_flow.
Its size is hardcoded to CONFIG_NR_CPUS bits, which can be
8192 by default, it costs memory and slows down ovs_flow_alloc.

To address this:
 Redefine cpu_used_mask to pointer.
 Append cpumask_size() bytes after 'stat' to hold cpumask.
 Initialization cpu_used_mask right after stats_last_writer.

APIs like cpumask_next and cpumask_set_cpu never access bits
beyond cpu count, cpumask_size() bytes of memory is enough.

Signed-off-by: default avatarEddy Tao <taoyuan_eddy@hotmail.com>
Acked-by: default avatarEelco Chaudron <echaudro@redhat.com>
Link: https://lore.kernel.org/r/OS3P286MB229570CCED618B20355D227AF5D59@OS3P286MB2295.JPNP286.PROD.OUTLOOK.COM


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent bbe64186

net/openvswitch/flow.c

+6 −3
Original line number Diff line number Diff line
@@ -107,7 +107,8 @@ 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);

					cpumask_set_cpu(cpu,

							flow->cpu_used_mask);

					goto unlock;

				}

			}
@@ -135,7 +136,8 @@ 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, &flow->cpu_used_mask)) {

	for (cpu = 0; cpu < nr_cpu_ids;

	     cpu = cpumask_next(cpu, flow->cpu_used_mask)) {

		struct sw_flow_stats *stats = rcu_dereference_ovsl(flow->stats[cpu]);



		if (stats) {
@@ -159,7 +161,8 @@ 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, &flow->cpu_used_mask)) {

	for (cpu = 0; cpu < nr_cpu_ids;

	     cpu = cpumask_next(cpu, flow->cpu_used_mask)) {

		struct sw_flow_stats *stats = ovsl_dereference(flow->stats[cpu]);



		if (stats) {

net/openvswitch/flow.h

+1 −1
Original line number Diff line number Diff line
@@ -229,7 +229,7 @@ struct sw_flow { 
					 */

	struct sw_flow_key key;

	struct sw_flow_id id;

	struct cpumask cpu_used_mask;

	struct cpumask *cpu_used_mask;

	struct sw_flow_mask *mask;

	struct sw_flow_actions __rcu *sf_acts;

	struct sw_flow_stats __rcu *stats[]; /* One for each CPU.  First one

net/openvswitch/flow_table.c

+5 −3
Original line number Diff line number Diff line
@@ -79,6 +79,7 @@ struct sw_flow *ovs_flow_alloc(void) 
		return ERR_PTR(-ENOMEM);



	flow->stats_last_writer = -1;

	flow->cpu_used_mask = (struct cpumask *)&flow->stats[nr_cpu_ids];



	/* Initialize the default stat node. */

	stats = kmem_cache_alloc_node(flow_stats_cache,
@@ -91,7 +92,7 @@ struct sw_flow *ovs_flow_alloc(void) 


	RCU_INIT_POINTER(flow->stats[0], stats);



	cpumask_set_cpu(0, &flow->cpu_used_mask);

	cpumask_set_cpu(0, flow->cpu_used_mask);



	return flow;

err:
@@ -115,7 +116,7 @@ static void flow_free(struct sw_flow *flow) 
					  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, &flow->cpu_used_mask)) {

	     cpu = cpumask_next(cpu, flow->cpu_used_mask)) {

		if (flow->stats[cpu])

			kmem_cache_free(flow_stats_cache,

					(struct sw_flow_stats __force *)flow->stats[cpu]);
@@ -1196,7 +1197,8 @@ int ovs_flow_init(void) 


	flow_cache = kmem_cache_create("sw_flow", sizeof(struct sw_flow)

				       + (nr_cpu_ids

					  * sizeof(struct sw_flow_stats *)),

					  * sizeof(struct sw_flow_stats *))

				       + cpumask_size(),

				       0, 0, NULL);

	if (flow_cache == NULL)

		return -ENOMEM;