Re: [PATCH v2 2/2] openvswitch: use percpu flow stats
flat view
From: Eric Dumazet <hidden>
Date: 2016-09-15 23:09:28
On Thu, 2016-09-15 at 19:11 -0300, Thadeu Lima de Souza Cascardo wrote:
Instead of using flow stats per NUMA node, use it per CPU. When using megaflows, the stats lock can be a bottleneck in scalability. On a E5-2690 12-core system, usual throughput went from ~4Mpps to ~15Mpps when forwarding between two 40GbE ports with a single flow configured on the datapath. This has been tested on a system with possible CPUs 0-7,16-23. After module removal, there were no corruption on the slab cache. Signed-off-by: Thadeu Lima de Souza Cascardo <redacted> Cc: pravin shelar <redacted> ---
quoted hunk ↗ jump to hunk
+ /* 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)) + if (flow->stats[cpu]) kmem_cache_free(flow_stats_cache, - (struct flow_stats __force *)flow->stats[node]); + (struct flow_stats __force *)flow->stats[cpu]); kmem_cache_free(flow_cache, flow); }@@ -757,7 +749,7 @@ int ovs_flow_init(void) BUILD_BUG_ON(sizeof(struct sw_flow_key) % sizeof(long)); flow_cache = kmem_cache_create("sw_flow", sizeof(struct sw_flow) - + (nr_node_ids + + (nr_cpu_ids * sizeof(struct flow_stats *)), 0, 0, NULL); if (flow_cache == NULL)
Well, if you switch to percpu stats, better use normal alloc_percpu(struct flow_stats) The code was dealing with per node allocation so could not use existing helper. No need to keep this forever.