[PATCH net-next 04/11] netfilter: flowtable: dedicated slab for flow entry
From: Florian Westphal <fw@strlen.de>
Date: 2026-02-05 11:09:33
Also in:
netfilter-devel
Subsystem:
netfilter, networking [general], the rest · Maintainers:
Pablo Neira Ayuso, Florian Westphal, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
From: Qingfang Deng <dqfext@gmail.com> The size of `struct flow_offload` has grown beyond 256 bytes on 64-bit kernels (currently 280 bytes) because of the `flow_offload_tunnel` member added recently. So kmalloc() allocates from the kmalloc-512 slab, causing significant memory waste per entry. Introduce a dedicated slab cache for flow entries to reduce memory footprint. Results in a reduction from 512 bytes to 320 bytes per entry on x86_64 kernels. Signed-off-by: Qingfang Deng <dqfext@gmail.com> Signed-off-by: Florian Westphal <fw@strlen.de> --- net/netfilter/nf_flow_table_core.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/net/netfilter/nf_flow_table_core.c b/net/netfilter/nf_flow_table_core.c
index 06e8251a6644..2c4140e6f53c 100644
--- a/net/netfilter/nf_flow_table_core.c
+++ b/net/netfilter/nf_flow_table_core.c@@ -16,6 +16,7 @@ static DEFINE_MUTEX(flowtable_lock); static LIST_HEAD(flowtables); +static __read_mostly struct kmem_cache *flow_offload_cachep; static void flow_offload_fill_dir(struct flow_offload *flow,
@@ -56,7 +57,7 @@ struct flow_offload *flow_offload_alloc(struct nf_conn *ct) if (unlikely(nf_ct_is_dying(ct))) return NULL; - flow = kzalloc(sizeof(*flow), GFP_ATOMIC); + flow = kmem_cache_zalloc(flow_offload_cachep, GFP_ATOMIC); if (!flow) return NULL;
@@ -812,9 +813,13 @@ static int __init nf_flow_table_module_init(void) { int ret; + flow_offload_cachep = KMEM_CACHE(flow_offload, SLAB_HWCACHE_ALIGN); + if (!flow_offload_cachep) + return -ENOMEM; + ret = register_pernet_subsys(&nf_flow_table_net_ops); if (ret < 0) - return ret; + goto out_pernet; ret = nf_flow_table_offload_init(); if (ret)
@@ -830,6 +835,8 @@ static int __init nf_flow_table_module_init(void) nf_flow_table_offload_exit(); out_offload: unregister_pernet_subsys(&nf_flow_table_net_ops); +out_pernet: + kmem_cache_destroy(flow_offload_cachep); return ret; }
@@ -837,6 +844,7 @@ static void __exit nf_flow_table_module_exit(void) { nf_flow_table_offload_exit(); unregister_pernet_subsys(&nf_flow_table_net_ops); + kmem_cache_destroy(flow_offload_cachep); } module_init(nf_flow_table_module_init);
--
2.52.0