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netfilter: flowtable: dedicated slab for flow entry

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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>
This commit is contained in:
Qingfang Deng
2026-01-30 15:22:07 +08:00
committed by Florian Westphal
parent 59ecffa399
commit 2a441a9aac
1 changed files with 10 additions and 2 deletions
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12
net/netfilter/nf_flow_table_core.c
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@@ -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 @@ out_bpf:
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);