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net: Pull out core bits of __netdev_alloc_skb and add __napi_alloc_skb

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This change pulls the core functionality out of __netdev_alloc_skb and
places them in a new function named __alloc_rx_skb.  The reason for doing
this is to make these bits accessible to a new function __napi_alloc_skb.
In addition __alloc_rx_skb now has a new flags value that is used to
determine which page frag pool to allocate from.  If the SKB_ALLOC_NAPI
flag is set then the NAPI pool is used.  The advantage of this is that we
do not have to use local_irq_save/restore when accessing the NAPI pool from
NAPI context.

In my test setup I saw at least 11ns of savings using the napi_alloc_skb
function versus the netdev_alloc_skb function, most of this being due to
the fact that we didn't have to call local_irq_save/restore.

The main use case for napi_alloc_skb would be for things such as copybreak
or page fragment based receive paths where an skb is allocated after the
data has been received instead of before.

Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Alexander Duyck 2014-12-09 19:40:49 -08:00 committed by David S. Miller
parent ffde7328a3
commit fd11a83dd3
3 changed files with 77 additions and 8 deletions
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9
include/linux/skbuff.h
View File

@ -151,6 +151,7 @@ struct net_device;
struct scatterlist;
struct pipe_inode_info;
struct iov_iter;
struct napi_struct;
#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
struct nf_conntrack {
@ -673,6 +674,7 @@ struct sk_buff {
#define SKB_ALLOC_FCLONE 0x01
#define SKB_ALLOC_RX 0x02
#define SKB_ALLOC_NAPI 0x04
/* Returns true if the skb was allocated from PFMEMALLOC reserves */
static inline bool skb_pfmemalloc(const struct sk_buff *skb)
@ -2165,6 +2167,13 @@ static inline struct sk_buff *netdev_alloc_skb_ip_align(struct net_device *dev,
}
void *napi_alloc_frag(unsigned int fragsz);
struct sk_buff *__napi_alloc_skb(struct napi_struct *napi,
unsigned int length, gfp_t gfp_mask);
static inline struct sk_buff *napi_alloc_skb(struct napi_struct *napi,
unsigned int length)
{
return __napi_alloc_skb(napi, length, GFP_ATOMIC);
}
/**
* __dev_alloc_pages - allocate page for network Rx

2
net/core/dev.c
View File

@ -4172,7 +4172,7 @@ struct sk_buff *napi_get_frags(struct napi_struct *napi)
struct sk_buff *skb = napi->skb;
if (!skb) {
skb = netdev_alloc_skb_ip_align(napi->dev, GRO_MAX_HEAD);
skb = napi_alloc_skb(napi, GRO_MAX_HEAD);
napi->skb = skb;
}
return skb;

74
net/core/skbuff.c
View File

@ -444,10 +444,13 @@ void *napi_alloc_frag(unsigned int fragsz)
EXPORT_SYMBOL(napi_alloc_frag);
/**
* __netdev_alloc_skb - allocate an skbuff for rx on a specific device
* @dev: network device to receive on
* __alloc_rx_skb - allocate an skbuff for rx
* @length: length to allocate
* @gfp_mask: get_free_pages mask, passed to alloc_skb
* @flags: If SKB_ALLOC_RX is set, __GFP_MEMALLOC will be used for
* allocations in case we have to fallback to __alloc_skb()
* If SKB_ALLOC_NAPI is set, page fragment will be allocated
* from napi_cache instead of netdev_cache.
*
* Allocate a new &sk_buff and assign it a usage count of one. The
* buffer has unspecified headroom built in. Users should allocate
@ -456,11 +459,11 @@ EXPORT_SYMBOL(napi_alloc_frag);
*
* %NULL is returned if there is no free memory.
*/
struct sk_buff *__netdev_alloc_skb(struct net_device *dev,
unsigned int length, gfp_t gfp_mask)
static struct sk_buff *__alloc_rx_skb(unsigned int length, gfp_t gfp_mask,
int flags)
{
struct sk_buff *skb = NULL;
unsigned int fragsz = SKB_DATA_ALIGN(length + NET_SKB_PAD) +
unsigned int fragsz = SKB_DATA_ALIGN(length) +
SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
if (fragsz <= PAGE_SIZE && !(gfp_mask & (__GFP_WAIT | GFP_DMA))) {
@ -469,7 +472,9 @@ struct sk_buff *__netdev_alloc_skb(struct net_device *dev,
if (sk_memalloc_socks())
gfp_mask |= __GFP_MEMALLOC;
data = __netdev_alloc_frag(fragsz, gfp_mask);
data = (flags & SKB_ALLOC_NAPI) ?
__napi_alloc_frag(fragsz, gfp_mask) :
__netdev_alloc_frag(fragsz, gfp_mask);
if (likely(data)) {
skb = build_skb(data, fragsz);
@ -477,17 +482,72 @@ struct sk_buff *__netdev_alloc_skb(struct net_device *dev,
put_page(virt_to_head_page(data));
}
} else {
skb = __alloc_skb(length + NET_SKB_PAD, gfp_mask,
skb = __alloc_skb(length, gfp_mask,
SKB_ALLOC_RX, NUMA_NO_NODE);
}
return skb;
}
/**
* __netdev_alloc_skb - allocate an skbuff for rx on a specific device
* @dev: network device to receive on
* @length: length to allocate
* @gfp_mask: get_free_pages mask, passed to alloc_skb
*
* Allocate a new &sk_buff and assign it a usage count of one. The
* buffer has NET_SKB_PAD headroom built in. Users should allocate
* the headroom they think they need without accounting for the
* built in space. The built in space is used for optimisations.
*
* %NULL is returned if there is no free memory.
*/
struct sk_buff *__netdev_alloc_skb(struct net_device *dev,
unsigned int length, gfp_t gfp_mask)
{
struct sk_buff *skb;
length += NET_SKB_PAD;
skb = __alloc_rx_skb(length, gfp_mask, 0);
if (likely(skb)) {
skb_reserve(skb, NET_SKB_PAD);
skb->dev = dev;
}
return skb;
}
EXPORT_SYMBOL(__netdev_alloc_skb);
/**
* __napi_alloc_skb - allocate skbuff for rx in a specific NAPI instance
* @napi: napi instance this buffer was allocated for
* @length: length to allocate
* @gfp_mask: get_free_pages mask, passed to alloc_skb and alloc_pages
*
* Allocate a new sk_buff for use in NAPI receive. This buffer will
* attempt to allocate the head from a special reserved region used
* only for NAPI Rx allocation. By doing this we can save several
* CPU cycles by avoiding having to disable and re-enable IRQs.
*
* %NULL is returned if there is no free memory.
*/
struct sk_buff *__napi_alloc_skb(struct napi_struct *napi,
unsigned int length, gfp_t gfp_mask)
{
struct sk_buff *skb;
length += NET_SKB_PAD + NET_IP_ALIGN;
skb = __alloc_rx_skb(length, gfp_mask, SKB_ALLOC_NAPI);
if (likely(skb)) {
skb_reserve(skb, NET_SKB_PAD + NET_IP_ALIGN);
skb->dev = napi->dev;
}
return skb;
}
EXPORT_SYMBOL(__napi_alloc_skb);
void skb_add_rx_frag(struct sk_buff *skb, int i, struct page *page, int off,
int size, unsigned int truesize)
{