xfrm: use a dedicated slab cache for struct xfrm_state (565f0fa9) · Commits · 戴 / test

struct xfrm_state is rather large (768 bytes here) and therefore wastes quite a lot of memory as it falls into the kmalloc-1024 slab cache, leaving 256 bytes of unused memory per XFRM state object -- a net waste of 25%. Using a dedicated slab cache for struct xfrm_state reduces the level of internal fragmentation to a minimum. On my configuration SLUB chooses to create a slab cache covering 4 pages holding 21 objects, resulting in an average memory waste of ~13 bytes per object -- a net waste of only 1.6%. In my tests this led to memory savings of roughly 2.3MB for 10k XFRM states. Signed-off-by:

Mathias Krause <minipli@googlemail.com> Signed-off-by:

Steffen Klassert <steffen.klassert@secunet.com>

net/xfrm/xfrm_state.c

+7 −2

Original line number	Diff line number	Diff line
		@@ -42,6 +42,7 @@ static void xfrm_state_gc_task(struct work_struct *work);

		static unsigned int xfrm_state_hashmax __read_mostly = 1 * 1024 * 1024;
		static __read_mostly seqcount_t xfrm_state_hash_generation = SEQCNT_ZERO(xfrm_state_hash_generation);
		static struct kmem_cache *xfrm_state_cache __ro_after_init;

		static DECLARE_WORK(xfrm_state_gc_work, xfrm_state_gc_task);
		static HLIST_HEAD(xfrm_state_gc_list);
		@@ -451,7 +452,7 @@ static void xfrm_state_gc_destroy(struct xfrm_state *x)
		}
		xfrm_dev_state_free(x);
		security_xfrm_state_free(x);
		kfree(x);
		kmem_cache_free(xfrm_state_cache, x);
		}

		static void xfrm_state_gc_task(struct work_struct *work)
		@@ -563,7 +564,7 @@ struct xfrm_state xfrm_state_alloc(struct net net)
		{
		struct xfrm_state *x;

		x = kzalloc(sizeof(struct xfrm_state), GFP_ATOMIC);
		x = kmem_cache_alloc(xfrm_state_cache, GFP_ATOMIC \| __GFP_ZERO);

		if (x) {
		write_pnet(&x->xs_net, net);
		@@ -2307,6 +2308,10 @@ int __net_init xfrm_state_init(struct net *net)
		{
		unsigned int sz;

		if (net_eq(net, &init_net))
		xfrm_state_cache = KMEM_CACHE(xfrm_state,
		SLAB_HWCACHE_ALIGN \| SLAB_PANIC);

		INIT_LIST_HEAD(&net->xfrm.state_all);

		sz = sizeof(struct hlist_head) * 8;

Admin message