From ffde7328a36d16e626bae8468571858d71cd010b Mon Sep 17 00:00:00 2001 From: Alexander Duyck Date: Tue, 9 Dec 2014 19:40:42 -0800 Subject: net: Split netdev_alloc_frag into __alloc_page_frag and add __napi_alloc_frag This patch splits the netdev_alloc_frag function up so that it can be used on one of two page frag pools instead of being fixed on the netdev_alloc_cache. By doing this we can add a NAPI specific function __napi_alloc_frag that accesses a pool that is only used from softirq context. The advantage to this is that we do not need to call local_irq_save/restore which can be a significant savings. I also took the opportunity to refactor the core bits that were placed in __alloc_page_frag. First I updated the allocation to do either a 32K allocation or an order 0 page. This is based on the changes in commmit d9b2938aa where it was found that latencies could be reduced in case of failures. Then I also rewrote the logic to work from the end of the page to the start. By doing this the size value doesn't have to be used unless we have run out of space for page fragments. Finally I cleaned up the atomic bits so that we just do an atomic_sub_and_test and if that returns true then we set the page->_count via an atomic_set. This way we can remove the extra conditional for the atomic_read since it would have led to an atomic_inc in the case of success anyway. Signed-off-by: Alexander Duyck Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller --- include/linux/skbuff.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux') diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index ab0bc43c82a4..736cc99f3f6c 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -2164,6 +2164,8 @@ static inline struct sk_buff *netdev_alloc_skb_ip_align(struct net_device *dev, return __netdev_alloc_skb_ip_align(dev, length, GFP_ATOMIC); } +void *napi_alloc_frag(unsigned int fragsz); + /** * __dev_alloc_pages - allocate page for network Rx * @gfp_mask: allocation priority. Set __GFP_NOMEMALLOC if not for network Rx -- cgit v1.3-14-g43fede From fd11a83dd3630ec6a60f8a702446532c5c7e1991 Mon Sep 17 00:00:00 2001 From: Alexander Duyck Date: Tue, 9 Dec 2014 19:40:49 -0800 Subject: net: Pull out core bits of __netdev_alloc_skb and add __napi_alloc_skb 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 Signed-off-by: David S. Miller --- include/linux/skbuff.h | 9 ++++++ net/core/dev.c | 2 +- net/core/skbuff.c | 74 +++++++++++++++++++++++++++++++++++++++++++++----- 3 files changed, 77 insertions(+), 8 deletions(-) (limited to 'include/linux') diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 736cc99f3f6c..85ab7d72b54c 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -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 diff --git a/net/core/dev.c b/net/core/dev.c index 3f191da383f6..80f798da3d9f 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -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; diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 56ed17cd2151..ae13ef6b3ea7 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -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) { -- cgit v1.3-14-g43fede