net: use hardware buffer pool to allocate skb

Message ID	1413343571-33231-1-git-send-email-Jiafei.Pan@freescale.com
State	Rejected, archived
Delegated to:	David Miller
Headers	show Return-Path: <netdev-owner@vger.kernel.org> From: Pan Jiafei <Jiafei.Pan@freescale.com> To: <davem@davemloft.net>, <jkosina@suse.cz> CC: <netdev@vger.kernel.org>, <Jiafei.Pan@freescale.com>, <LeoLi@freescale.com>, <linux-doc@vger.kernel.org> Subject: [PATCH] net: use hardware buffer pool to allocate skb Date: Wed, 15 Oct 2014 11:26:11 +0800 Message-ID: <1413343571-33231-1-git-send-email-Jiafei.Pan@freescale.com> MIME-Version: 1.0 Content-Type: text/plain Received-SPF: Fail (protection.outlook.com: domain of freescale.com does not designate 192.88.158.2 as permitted sender) receiver=protection.outlook.com; client-ip=192.88.158.2; helo=az84smr01.freescale.net; Sender: netdev-owner@vger.kernel.org Precedence: bulk

diff --git a/Documentation/networking/hw_skb.txt b/Documentation/networking/hw_skb.txt new file mode 100644 index 0000000..256f3fc --- /dev/null +++ b/Documentation/networking/hw_skb.txt @@ -0,0 +1,117 @@ +Document for using hardware managed SKB. + +1. Description + +In some platform, there are some hardware block provided +to manage buffers to improve performance. So in some case, +it is expected that the packets received by some generic +NIC should be put into such hardware managed buffers +directly, so that such buffer can be released by hardware +or by driver. + +2. Related Struct Definition + +Some general APIs are provided for generic NIC to use hardware +block managed buffers without any modification for generic NIC +drivers. + +1)Kernel Configuration Item + + "CONFIG_USE_HW_SKB" + +2)The DEVICE structure + + struct net_device { + ... + #ifdef CONFIG_USE_HW_SKB + void *hw_skb_priv; + struct sk_buff *(*alloc_hw_skb)(void *hw_skb_priv, unsigned int length); + void (*free_hw_skb)(struct sk_buff *skb); + #endif + ... + } + +"hw_skb_priv" is private data for "alloc_hw_skb" and "free_hw_skb" functions. +"alloc_hw_skb" is for allocating skb by using hardware managed buffer. +"free_hw_skb" is for freeing skb allocated by hardware manager buffer. + +3)struct sk_buff - socket buffer + + struct sk_buff { + ... + #ifdef CONFIG_SKB_USE_HW_BP + __u32 hw_skb_state; + void *hw_skb_priv; + void (*free_hw_skb)(struct sk_buff *skb); + #endif + ... + } + + /* hw_skb_state list */ + enum hw_skb_state { + /* If set, SKB use hardware managed buffer */ + IS_HW_SKB = 1 << 0, + /* If set, and skb can be freed by software by calling + * netdev->free_hw_skb + */ + HW_SKB_SW_FREE = 1 << 1, + }; + +"hw_skb_priv" and "free_hw_skb" are the same with the field in the +struct "net_device" + +After calling "alloc_hw_skb" to allocate skb by using hardware managed +buffers, "hw_skb_priv" and "free_hw_skb" is set in SKB driver: + skb->hw_skb_priv = dev->hw_skb_priv; + skb->free_hw_skb = dev->free_hw_skb; +So that when "struct net_device *dev" is changed after the skb is allocated, +It is be confirmed that this skb can be freed by the method synced +with allocation. + +"hw_skb_state" indicates that the state of SKB. When the skb is allocated +by "alloc_hw_skb" function, the flag of "IS_HW_SKB" is set by +"__netdev_alloc_skb" function in skbuff.c when returned from "alloc_hw_skb". +But in "alloc_hw_skb", "HW_SKB_SW_FREE" must be set if the skb should be +freed by calling "free_hw_skb", otherwise, the skb will never be freed by +any driver until it is freed by hardware block. + +SKB using hardware managed buffer is not recycleable. + +3. How to use this feature + +For example, driver "A" wants the third-party NIC driver "B" to +store the data in some hardware managed buffer then send to "A". + +1) Select "CONFIG_USE_HW_SKB" to enable this feature. + +2) In driver "A", implement the function "alloc_hw_skb" and +"free_hw_skb". For example: + +struct sk_buff *alloc_hw_skb(void *priv, unsigned int length) +{ + buf = alloc_hw_buffer(); + skb = build_skb(buf, ...); + if (skb) + skb->hw_skb_state |= HW_SKB_SW_FREE; + + return skb; +} + +void free_hw_skb(struct sk_buff *skb) +{ + free_hw_buffer(skb->head); +} + +3) In driver "A", get "net_device" handle of net device case using +driver "B". + ... + net_dev_b->hw_skb_priv = priv; + net_dev_b->alloc_hw_skb = alloc_hw_skb; + net_dev_b->free_hw_skb = free_hw_skb; + ... + +4) Then, when driver "B" wants to allocate skb, "alloc_hw_skb" +will be called to allocate hardware manager skb firstly, if +failed, the normal skb will also be allocate, if successed, +the skb will be freed by calling free_hw_skb when "kfree_skb" +is called to free this skb. diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 838407a..42b6158 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -1689,6 +1689,11 @@ struct net_device { struct lock_class_key *qdisc_tx_busylock; int group; struct pm_qos_request pm_qos_req; +#ifdef CONFIG_USE_HW_SKB + void *hw_skb_priv; + struct sk_buff *(*alloc_hw_skb)(void *hw_skb_priv, unsigned int length); + void (*free_hw_skb)(struct sk_buff *skb); +#endif }; #define to_net_dev(d) container_of(d, struct net_device, dev) diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 776104b..d9afdeb 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -436,6 +436,16 @@ static inline u32 skb_mstamp_us_delta(const struct skb_mstamp *t1, } +/* hw_skb_state list */ +enum hw_skb_state { + /* If set, SKB use hardware managed buffer */ + IS_HW_SKB = 1 << 0, + /* If set, and skb can be freed by software by calling + * netdev->free_hw_skb + */ + HW_SKB_SW_FREE = 1 << 1, +}; + /** * struct sk_buff - socket buffer * @next: Next buffer in list @@ -646,6 +656,12 @@ struct sk_buff { __u16 network_header; __u16 mac_header; +#ifdef CONFIG_USE_HW_SKB + __u32 hw_skb_state; + void *hw_skb_priv; + void (*free_hw_skb)(struct sk_buff *skb); +#endif + __u32 headers_end[0]; /* These elements must be at the end, see alloc_skb() for details. */ diff --git a/net/Kconfig b/net/Kconfig index d6b138e..346e021 100644 --- a/net/Kconfig +++ b/net/Kconfig @@ -291,6 +291,16 @@ config NET_FLOW_LIMIT with many clients some protection against DoS by a single (spoofed) flow that greatly exceeds average workload. +config USE_HW_SKB + bool "NIC use hardware managed buffer to build skb" + depends on INET + ---help--- + If select this, the third party drivers will use hardware managed + buffers to allocate SKB without any modification for the driver. + + Documentation on how to use this featue can be found at + <file:Documentation/networking/hw_skb.txt>. + menu "Network testing" config NET_PKTGEN diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 7b3df0d..f8603e5 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -415,6 +415,19 @@ struct sk_buff *__netdev_alloc_skb(struct net_device *dev, unsigned int fragsz = SKB_DATA_ALIGN(length + NET_SKB_PAD) + SKB_DATA_ALIGN(sizeof(struct skb_shared_info)); +#ifdef CONFIG_USE_HW_SKB + if (dev->alloc_hw_skb) { + skb = dev->alloc_hw_skb(dev->hw_skb_priv, length); + if (likely(skb)) { + skb->hw_skb_state |= IS_HW_SKB; + skb->hw_skb_priv = dev->hw_skb_priv; + skb->free_hw_skb = dev->free_hw_skb; + skb_reserve(skb, NET_SKB_PAD); + skb->dev = dev; + return skb; + } + } +#endif if (fragsz <= PAGE_SIZE && !(gfp_mask & (__GFP_WAIT | GFP_DMA))) { void *data; @@ -432,6 +445,7 @@ struct sk_buff *__netdev_alloc_skb(struct net_device *dev, skb = __alloc_skb(length + NET_SKB_PAD, gfp_mask, SKB_ALLOC_RX, NUMA_NO_NODE); } + if (likely(skb)) { skb_reserve(skb, NET_SKB_PAD); skb->dev = dev; @@ -483,6 +497,15 @@ static void skb_clone_fraglist(struct sk_buff *skb) static void skb_free_head(struct sk_buff *skb) { +#ifdef CONFIG_USE_HW_SKB + if (skb->hw_skb_state & IS_HW_SKB) { + if (skb->hw_skb_state & HW_SKB_SW_FREE) { + BUG_ON(!skb->free_hw_skb); + skb->free_hw_skb(skb); + } + return; + } +#endif if (skb->head_frag) put_page(virt_to_head_page(skb->head)); else @@ -506,6 +529,10 @@ static void skb_release_data(struct sk_buff *skb) * If skb buf is from userspace, we need to notify the caller * the lower device DMA has done; */ +#ifdef CONFIG_USE_HW_SKB + if (skb->hw_skb_state & IS_HW_SKB) + goto skip_callback; +#endif if (shinfo->tx_flags & SKBTX_DEV_ZEROCOPY) { struct ubuf_info *uarg; @@ -514,6 +541,7 @@ static void skb_release_data(struct sk_buff *skb) uarg->callback(uarg, true); } +skip_callback: if (shinfo->frag_list) kfree_skb_list(shinfo->frag_list);

net: use hardware buffer pool to allocate skb

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