提交 795bb1c0 编写于 作者: J Jesper Dangaard Brouer 提交者: David S. Miller

net: bulk free infrastructure for NAPI context, use napi_consume_skb

Discovered that network stack were hitting the kmem_cache/SLUB
slowpath when freeing SKBs.  Doing bulk free with kmem_cache_free_bulk
can speedup this slowpath.

NAPI context is a bit special, lets take advantage of that for bulk
free'ing SKBs.

In NAPI context we are running in softirq, which gives us certain
protection.  A softirq can run on several CPUs at once.  BUT the
important part is a softirq will never preempt another softirq running
on the same CPU.  This gives us the opportunity to access per-cpu
variables in softirq context.

Extend napi_alloc_cache (before only contained page_frag_cache) to be
a struct with a small array based stack for holding SKBs.  Introduce a
SKB defer and flush API for accessing this.

Introduce napi_consume_skb() as replacement for e.g. dev_consume_skb_any()
when running in NAPI context.  A small trick to handle/detect if we
are called from netpoll is to see if budget is 0.  In that case, we
need to invoke dev_consume_skb_irq().

Joint work with Alexander Duyck.
Signed-off-by: NJesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: NAlexander Duyck <alexander.h.duyck@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
上级 18ac5590
......@@ -2404,6 +2404,9 @@ static inline struct sk_buff *napi_alloc_skb(struct napi_struct *napi,
{
return __napi_alloc_skb(napi, length, GFP_ATOMIC);
}
void napi_consume_skb(struct sk_buff *skb, int budget);
void __kfree_skb_flush(void);
/**
* __dev_alloc_pages - allocate page for network Rx
......
......@@ -5155,6 +5155,7 @@ static void net_rx_action(struct softirq_action *h)
}
}
__kfree_skb_flush();
local_irq_disable();
list_splice_tail_init(&sd->poll_list, &list);
......
......@@ -347,8 +347,16 @@ struct sk_buff *build_skb(void *data, unsigned int frag_size)
}
EXPORT_SYMBOL(build_skb);
#define NAPI_SKB_CACHE_SIZE 64
struct napi_alloc_cache {
struct page_frag_cache page;
size_t skb_count;
void *skb_cache[NAPI_SKB_CACHE_SIZE];
};
static DEFINE_PER_CPU(struct page_frag_cache, netdev_alloc_cache);
static DEFINE_PER_CPU(struct page_frag_cache, napi_alloc_cache);
static DEFINE_PER_CPU(struct napi_alloc_cache, napi_alloc_cache);
static void *__netdev_alloc_frag(unsigned int fragsz, gfp_t gfp_mask)
{
......@@ -378,9 +386,9 @@ EXPORT_SYMBOL(netdev_alloc_frag);
static void *__napi_alloc_frag(unsigned int fragsz, gfp_t gfp_mask)
{
struct page_frag_cache *nc = this_cpu_ptr(&napi_alloc_cache);
struct napi_alloc_cache *nc = this_cpu_ptr(&napi_alloc_cache);
return __alloc_page_frag(nc, fragsz, gfp_mask);
return __alloc_page_frag(&nc->page, fragsz, gfp_mask);
}
void *napi_alloc_frag(unsigned int fragsz)
......@@ -474,7 +482,7 @@ EXPORT_SYMBOL(__netdev_alloc_skb);
struct sk_buff *__napi_alloc_skb(struct napi_struct *napi, unsigned int len,
gfp_t gfp_mask)
{
struct page_frag_cache *nc = this_cpu_ptr(&napi_alloc_cache);
struct napi_alloc_cache *nc = this_cpu_ptr(&napi_alloc_cache);
struct sk_buff *skb;
void *data;
......@@ -494,7 +502,7 @@ struct sk_buff *__napi_alloc_skb(struct napi_struct *napi, unsigned int len,
if (sk_memalloc_socks())
gfp_mask |= __GFP_MEMALLOC;
data = __alloc_page_frag(nc, len, gfp_mask);
data = __alloc_page_frag(&nc->page, len, gfp_mask);
if (unlikely(!data))
return NULL;
......@@ -505,7 +513,7 @@ struct sk_buff *__napi_alloc_skb(struct napi_struct *napi, unsigned int len,
}
/* use OR instead of assignment to avoid clearing of bits in mask */
if (nc->pfmemalloc)
if (nc->page.pfmemalloc)
skb->pfmemalloc = 1;
skb->head_frag = 1;
......@@ -747,6 +755,69 @@ void consume_skb(struct sk_buff *skb)
}
EXPORT_SYMBOL(consume_skb);
void __kfree_skb_flush(void)
{
struct napi_alloc_cache *nc = this_cpu_ptr(&napi_alloc_cache);
/* flush skb_cache if containing objects */
if (nc->skb_count) {
kmem_cache_free_bulk(skbuff_head_cache, nc->skb_count,
nc->skb_cache);
nc->skb_count = 0;
}
}
static void __kfree_skb_defer(struct sk_buff *skb)
{
struct napi_alloc_cache *nc = this_cpu_ptr(&napi_alloc_cache);
/* drop skb->head and call any destructors for packet */
skb_release_all(skb);
/* record skb to CPU local list */
nc->skb_cache[nc->skb_count++] = skb;
#ifdef CONFIG_SLUB
/* SLUB writes into objects when freeing */
prefetchw(skb);
#endif
/* flush skb_cache if it is filled */
if (unlikely(nc->skb_count == NAPI_SKB_CACHE_SIZE)) {
kmem_cache_free_bulk(skbuff_head_cache, NAPI_SKB_CACHE_SIZE,
nc->skb_cache);
nc->skb_count = 0;
}
}
void napi_consume_skb(struct sk_buff *skb, int budget)
{
if (unlikely(!skb))
return;
/* if budget is 0 assume netpoll w/ IRQs disabled */
if (unlikely(!budget)) {
dev_consume_skb_irq(skb);
return;
}
if (likely(atomic_read(&skb->users) == 1))
smp_rmb();
else if (likely(!atomic_dec_and_test(&skb->users)))
return;
/* if reaching here SKB is ready to free */
trace_consume_skb(skb);
/* if SKB is a clone, don't handle this case */
if (unlikely(skb->fclone != SKB_FCLONE_UNAVAILABLE)) {
__kfree_skb(skb);
return;
}
__kfree_skb_defer(skb);
}
EXPORT_SYMBOL(napi_consume_skb);
/* Make sure a field is enclosed inside headers_start/headers_end section */
#define CHECK_SKB_FIELD(field) \
BUILD_BUG_ON(offsetof(struct sk_buff, field) < \
......
Markdown is supported
0% .
You are about to add 0 people to the discussion. Proceed with caution.
先完成此消息的编辑!
想要评论请 注册