Commit a5cd3a60 authored by Eric Dumazet's avatar Eric Dumazet Committed by Jakub Kicinski
Browse files

net: shrink napi_skb_cache_{put,get}() and napi_skb_cache_get_bulk() 



Following loop in napi_skb_cache_put() is unrolled by the compiler
even if CONFIG_KASAN is not enabled:

for (i = NAPI_SKB_CACHE_HALF; i < NAPI_SKB_CACHE_SIZE; i++)
	kasan_mempool_unpoison_object(nc->skb_cache[i],
				kmem_cache_size(net_hotdata.skbuff_cache));

We have 32 times this sequence, for a total of 384 bytes.

	48 8b 3d 00 00 00 00 	net_hotdata.skbuff_cache,%rdi
	e8 00 00 00 00       	call   kmem_cache_size

This is because kmem_cache_size() is not an inline and not const,
and kasan_unpoison_object_data() is an inline function.

Cache kmem_cache_size() result in a variable, so that
the compiler can remove dead code (and variable) when/if
CONFIG_KASAN is unset.

After this patch, napi_skb_cache_put() is inlined in its callers,
and we avoid one kmem_cache_size() call in napi_skb_cache_get()
and napi_skb_cache_get_bulk().

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarJacob Keller <jacob.e.keller@intel.com>
Reviewed-by: default avatarKuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: default avatarAlexander Lobakin <aleksander.lobakin@intel.com>
Link: https://patch.msgid.link/20251016182911.1132792-1-edumazet@google.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 6ae022f8

net/core/skbuff.c

+10 −5
Original line number Diff line number Diff line
@@ -274,6 +274,11 @@ void *__netdev_alloc_frag_align(unsigned int fragsz, unsigned int align_mask) 
}

EXPORT_SYMBOL(__netdev_alloc_frag_align);



/* Cache kmem_cache_size(net_hotdata.skbuff_cache) to help the compiler

 * remove dead code (and skbuff_cache_size) when CONFIG_KASAN is unset.

 */

static u32 skbuff_cache_size __read_mostly;



static struct sk_buff *napi_skb_cache_get(void)

{

	struct napi_alloc_cache *nc = this_cpu_ptr(&napi_alloc_cache);
@@ -293,7 +298,7 @@ static struct sk_buff *napi_skb_cache_get(void) 


	skb = nc->skb_cache[--nc->skb_count];

	local_unlock_nested_bh(&napi_alloc_cache.bh_lock);

	kasan_mempool_unpoison_object(skb, kmem_cache_size(net_hotdata.skbuff_cache));

	kasan_mempool_unpoison_object(skb, skbuff_cache_size);



	return skb;

}
@@ -345,11 +350,9 @@ u32 napi_skb_cache_get_bulk(void **skbs, u32 n) 


get:

	for (u32 base = nc->skb_count - n, i = 0; i < n; i++) {

		u32 cache_size = kmem_cache_size(net_hotdata.skbuff_cache);



		skbs[i] = nc->skb_cache[base + i];



		kasan_mempool_unpoison_object(skbs[i], cache_size);

		kasan_mempool_unpoison_object(skbs[i], skbuff_cache_size);

		memset(skbs[i], 0, offsetof(struct sk_buff, tail));

	}
@@ -1437,7 +1440,7 @@ static void napi_skb_cache_put(struct sk_buff *skb) 
	if (unlikely(nc->skb_count == NAPI_SKB_CACHE_SIZE)) {

		for (i = NAPI_SKB_CACHE_HALF; i < NAPI_SKB_CACHE_SIZE; i++)

			kasan_mempool_unpoison_object(nc->skb_cache[i],

						kmem_cache_size(net_hotdata.skbuff_cache));

						skbuff_cache_size);



		kmem_cache_free_bulk(net_hotdata.skbuff_cache, NAPI_SKB_CACHE_HALF,

				     nc->skb_cache + NAPI_SKB_CACHE_HALF);
@@ -5125,6 +5128,8 @@ void __init skb_init(void) 
					      offsetof(struct sk_buff, cb),

					      sizeof_field(struct sk_buff, cb),

					      NULL);

	skbuff_cache_size = kmem_cache_size(net_hotdata.skbuff_cache);



	net_hotdata.skbuff_fclone_cache = kmem_cache_create("skbuff_fclone_cache",

						sizeof(struct sk_buff_fclones),

						0,