Messages in this thread | | | From | Eelco Chaudron <> | Subject | Re: [ovs-dev] [PATCH net-next v3 1/1] net:openvswitch:reduce cpu_used_mask memory | Date | Thu, 02 Feb 2023 12:44:47 +0100 |
| |
On 2 Feb 2023, at 12:26, 陶 缘 wrote:
> Hi, Eelco: > > Thanks for your time going through the detail. > The thing is: sizeof(struct cpumask), with default CONFIG_NR_CPUS 8192, has a size of 1024 bytes even on a system with only 4 cpus. > While in practice the cpumask APIs like cpumask_next and cpumask_set_cpu never access more than cpumask_size() of bytes in the bitmap > My change used cpumask_size() (in above example, consume 8 bytes after alignement for the cpumask, it saved 1016 bytes for every flow.
I looked at the wrong nr_cpumask_bits definition, so thanks for this education :)
> Your question reminded me to revisit the description "as well as the iteration of bits in cpu_used_mask", after a second think, this statement is not valid and should be removed. > since the iteration API will not access the number of bytes decided by nr_cpu_ids(running CPUs) > > I will remove this statement after solving a final style issue in the next submission.
Thanks!
> Thanks > eddy > ________________________________ > 发件人: Eelco Chaudron <echaudro@redhat.com> > 发送时间: 2023年2月2日 11:05 > 收件人: Eddy Tao <taoyuan_eddy@hotmail.com> > 抄送: netdev@vger.kernel.org <netdev@vger.kernel.org>; dev@openvswitch.org <dev@openvswitch.org>; linux-kernel@vger.kernel.org <linux-kernel@vger.kernel.org>; Eric Dumazet <edumazet@google.com>; Jakub Kicinski <kuba@kernel.org>; Paolo Abeni <pabeni@redhat.com>; David S. Miller <davem@davemloft.net> > 主题: Re: [ovs-dev] [PATCH net-next v3 1/1] net:openvswitch:reduce cpu_used_mask memory > > > > On 2 Feb 2023, at 11:32, Eddy Tao wrote: > >> 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 >> as well as the iteration of bits in cpu_used_mask when handling >> netlink message from ofproto > > I’m trying to understand how this will decrease memory usage. The size of the flow_cache stayed the same (actually it’s large due to the extra pointer). > > Also do not understand why the iteration is less, as the mask is initialized the same. > > Cheers, > > Eelco > >> To address this, redefine cpu_used_mask to pointer >> append cpumask_size() bytes after 'stat' to hold cpumask >> >> cpumask APIs like cpumask_next and cpumask_set_cpu never access >> bits beyond cpu count, cpumask_size() bytes of memory is enough >> >> Signed-off-by: Eddy Tao <taoyuan_eddy@hotmail.com> >> --- >> net/openvswitch/flow.c | 8 +++++--- >> net/openvswitch/flow.h | 2 +- >> net/openvswitch/flow_table.c | 8 +++++--- >> 3 files changed, 11 insertions(+), 7 deletions(-) >> >> diff --git a/net/openvswitch/flow.c b/net/openvswitch/flow.c >> index e20d1a973417..0109a5f86f6a 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 +135,8 @@ 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 +160,8 @@ 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) { >> 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..dc6a174c3194 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]); >> @@ -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; >> -- >> 2.27.0 >> >> _______________________________________________ >> dev mailing list >> dev@openvswitch.org >> https://mail.openvswitch.org/mailman/listinfo/ovs-dev
| |