| Message ID | OS3P286MB2295C30BCD41592C25805136F5D09@OS3P286MB2295.JPNP286.PROD.OUTLOOK.COM (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | net: openvswitch: reduce cpu_used_mask memory consumption | expand |
Tue, Jan 31, 2023 at 02:58:22PM CET, taoyuan_eddy@hotmail.com wrote: >From: eddytaoyuan <taoyuan_eddy@hotmail.com> > >struct cpumask cpu_used_mask is directly embedded in struct sw_flow >however, its size is hardcoded to CONFIG_NR_CPUS bits, which >can be as large as 8192 by default, it cost memory and slows down >ovs_flow_alloc, this fix used actual CPU number instead > >Signed-off-by: eddytaoyuan <taoyuan_eddy@hotmail.com> Hmm, I guess that the name should be rather "Dddy Taoyuan" ? Please fix, also in your "From:" header and preferably email client. >--- > net/openvswitch/flow.c | 6 +++--- > net/openvswitch/flow.h | 2 +- > net/openvswitch/flow_table.c | 25 ++++++++++++++++++++++--- > 3 files changed, 26 insertions(+), 7 deletions(-) > >diff --git a/net/openvswitch/flow.c b/net/openvswitch/flow.c >index e20d1a973417..06345cd8c777 100644 >--- a/net/openvswitch/flow.c >+++ b/net/openvswitch/flow.c >@@ -107,7 +107,7 @@ 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); >+ cpumask_set_cpu(cpu, flow->cpu_used_mask); > goto unlock; > } > } >@@ -135,7 +135,7 @@ 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, &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 +159,7 @@ 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, &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) { >diff --git a/net/openvswitch/flow.h b/net/openvswitch/flow.h >index 073ab73ffeaa..b5711aff6e76 100644 >--- a/net/openvswitch/flow.h >+++ b/net/openvswitch/flow.h >@@ -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 >diff --git a/net/openvswitch/flow_table.c b/net/openvswitch/flow_table.c >index 0a0e4c283f02..c0fdff73272f 100644 >--- a/net/openvswitch/flow_table.c >+++ b/net/openvswitch/flow_table.c >@@ -87,11 +87,12 @@ struct sw_flow *ovs_flow_alloc(void) > if (!stats) > goto err; > >+ flow->cpu_used_mask = (struct cpumask *)&(flow->stats[nr_cpu_ids]); > spin_lock_init(&stats->lock); > > 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]); >@@ -1194,9 +1195,27 @@ int ovs_flow_init(void) > BUILD_BUG_ON(__alignof__(struct sw_flow_key) % __alignof__(long)); > BUILD_BUG_ON(sizeof(struct sw_flow_key) % sizeof(long)); > >+ /* >+ * Simply including 'struct cpumask' in 'struct sw_flow' >+ * consumes memory unnecessarily large. >+ * The reason is that compilation option CONFIG_NR_CPUS(default 8192) >+ * decides the value of NR_CPUS, which in turn decides size of >+ * 'struct cpumask', which means 1024 bytes are needed for the cpumask >+ * It affects ovs_flow_alloc performance as well as memory footprint. >+ * We should use actual CPU count instead of hardcoded value. >+ * >+ * To address this, 'cpu_used_mask' is redefined to pointer >+ * and append a cpumask_size() after 'stat' to hold the actual memory >+ * of struct cpumask >+ * >+ * cpumask APIs like cpumask_next and cpumask_set_cpu have been defined >+ * to never access bits beyond cpu count by design, thus above change is >+ * safe even though the actual memory provided is smaller than >+ * sizeof(struct cpumask) I don't understand the reason to have this comment in the code. From what I see, this should be moved to the patch description. Of course with changing the mood to imperation when you say the codebase what to do. >+ */ > 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; >-- >2.27.0 >
diff --git a/net/openvswitch/flow.c b/net/openvswitch/flow.c index e20d1a973417..06345cd8c777 100644 --- a/net/openvswitch/flow.c +++ b/net/openvswitch/flow.c @@ -107,7 +107,7 @@ 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); + cpumask_set_cpu(cpu, flow->cpu_used_mask); goto unlock; } } @@ -135,7 +135,7 @@ 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, &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 +159,7 @@ 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, &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) { diff --git a/net/openvswitch/flow.h b/net/openvswitch/flow.h index 073ab73ffeaa..b5711aff6e76 100644 --- a/net/openvswitch/flow.h +++ b/net/openvswitch/flow.h @@ -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 diff --git a/net/openvswitch/flow_table.c b/net/openvswitch/flow_table.c index 0a0e4c283f02..c0fdff73272f 100644 --- a/net/openvswitch/flow_table.c +++ b/net/openvswitch/flow_table.c @@ -87,11 +87,12 @@ struct sw_flow *ovs_flow_alloc(void) if (!stats) goto err; + flow->cpu_used_mask = (struct cpumask *)&(flow->stats[nr_cpu_ids]); spin_lock_init(&stats->lock); 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]); @@ -1194,9 +1195,27 @@ int ovs_flow_init(void) BUILD_BUG_ON(__alignof__(struct sw_flow_key) % __alignof__(long)); BUILD_BUG_ON(sizeof(struct sw_flow_key) % sizeof(long)); + /* + * Simply including 'struct cpumask' in 'struct sw_flow' + * consumes memory unnecessarily large. + * The reason is that compilation option CONFIG_NR_CPUS(default 8192) + * decides the value of NR_CPUS, which in turn decides size of + * 'struct cpumask', which means 1024 bytes are needed for the cpumask + * It affects ovs_flow_alloc performance as well as memory footprint. + * We should use actual CPU count instead of hardcoded value. + * + * To address this, 'cpu_used_mask' is redefined to pointer + * and append a cpumask_size() after 'stat' to hold the actual memory + * of struct cpumask + * + * cpumask APIs like cpumask_next and cpumask_set_cpu have been defined + * to never access bits beyond cpu count by design, thus above change is + * safe even though the actual memory provided is smaller than + * sizeof(struct cpumask) + */ 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;