Currently, when you send an XSk frame with metadata, you need to do the following: * call external xsk_buff_raw_get_dma(); * call inline xsk_buff_get_metadata(), which calls external xsk_buff_raw_get_data() and then do some inline checks. This effectively means that the following piece: addr = pool->unaligned ? xp_unaligned_add_offset_to_addr(addr) : addr; is done twice per frame, plus you have 2 external calls per frame, plus this: meta = pool->addrs + addr - pool->tx_metadata_len; if (unlikely(!xsk_buff_valid_tx_metadata(meta))) is always inlined, even if there's no meta or it's invalid. Add xsk_buff_raw_get_ctx() (xp_raw_get_ctx() to be precise) to do that in one go. It returns a small structure with 2 fields: DMA address, filled unconditionally, and metadata pointer, valid only if it's present. The address correction is performed only once and you also have only 1 external call per XSk frame, which does all the calculations and checks outside of your hotpath. You only need to check `if (ctx.meta)` for the metadata presence. Signed-off-by: Alexander Lobakin <aleksander.lobakin@xxxxxxxxx> --- include/net/xdp_sock_drv.h | 23 +++++++++++++++++++++ include/net/xsk_buff_pool.h | 8 ++++++++ net/xdp/xsk_buff_pool.c | 40 +++++++++++++++++++++++++++++++++++++ 3 files changed, 71 insertions(+) diff --git a/include/net/xdp_sock_drv.h b/include/net/xdp_sock_drv.h index 86620c818965..7fd1709deef5 100644 --- a/include/net/xdp_sock_drv.h +++ b/include/net/xdp_sock_drv.h @@ -205,6 +205,23 @@ static inline void *xsk_buff_raw_get_data(struct xsk_buff_pool *pool, u64 addr) return xp_raw_get_data(pool, addr); } +/** + * xsk_buff_raw_get_ctx - get &xdp_desc context + * @pool: XSk buff pool desc address belongs to + * @addr: desc address (from userspace) + * + * Wrapper for xp_raw_get_ctx() to be used in drivers, see its kdoc for + * details. + * + * Return: new &xdp_desc_ctx struct containing desc's DMA address and metadata + * pointer, if it is present and valid (initialized to %NULL otherwise). + */ +static inline struct xdp_desc_ctx +xsk_buff_raw_get_ctx(const struct xsk_buff_pool *pool, u64 addr) +{ + return xp_raw_get_ctx(pool, addr); +} + #define XDP_TXMD_FLAGS_VALID ( \ XDP_TXMD_FLAGS_TIMESTAMP | \ XDP_TXMD_FLAGS_CHECKSUM | \ @@ -402,6 +419,12 @@ static inline void *xsk_buff_raw_get_data(struct xsk_buff_pool *pool, u64 addr) return NULL; } +static inline struct xdp_desc_ctx +xsk_buff_raw_get_ctx(const struct xsk_buff_pool *pool, u64 addr) +{ + return (struct xdp_desc_ctx){ }; +} + static inline bool xsk_buff_valid_tx_metadata(struct xsk_tx_metadata *meta) { return false; diff --git a/include/net/xsk_buff_pool.h b/include/net/xsk_buff_pool.h index 50779406bc2d..1dcd4d71468a 100644 --- a/include/net/xsk_buff_pool.h +++ b/include/net/xsk_buff_pool.h @@ -141,6 +141,14 @@ u32 xp_alloc_batch(struct xsk_buff_pool *pool, struct xdp_buff **xdp, u32 max); bool xp_can_alloc(struct xsk_buff_pool *pool, u32 count); void *xp_raw_get_data(struct xsk_buff_pool *pool, u64 addr); dma_addr_t xp_raw_get_dma(struct xsk_buff_pool *pool, u64 addr); + +struct xdp_desc_ctx { + dma_addr_t dma; + struct xsk_tx_metadata *meta; +}; + +struct xdp_desc_ctx xp_raw_get_ctx(const struct xsk_buff_pool *pool, u64 addr); + static inline dma_addr_t xp_get_dma(struct xdp_buff_xsk *xskb) { return xskb->dma; diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c index 1f7975b49657..4ea742da304d 100644 --- a/net/xdp/xsk_buff_pool.c +++ b/net/xdp/xsk_buff_pool.c @@ -714,3 +714,43 @@ dma_addr_t xp_raw_get_dma(struct xsk_buff_pool *pool, u64 addr) (addr & ~PAGE_MASK); } EXPORT_SYMBOL(xp_raw_get_dma); + +/** + * xp_raw_get_ctx - get &xdp_desc context + * @pool: XSk buff pool desc address belongs to + * @addr: desc address (from userspace) + * + * Helper for getting desc's DMA address and metadata pointer, if present. + * Saves one call on hotpath, double calculation of the actual address, + * and inline checks for metadata presence and sanity. + * Please use xsk_buff_raw_get_ctx() in drivers instead. + * + * Return: new &xdp_desc_ctx struct containing desc's DMA address and metadata + * pointer, if it is present and valid (initialized to %NULL otherwise). + */ +struct xdp_desc_ctx xp_raw_get_ctx(const struct xsk_buff_pool *pool, u64 addr) +{ + struct xsk_tx_metadata *meta; + struct xdp_desc_ctx ret; + + addr = pool->unaligned ? xp_unaligned_add_offset_to_addr(addr) : addr; + ret = (typeof(ret)){ + /* Same logic as in xp_raw_get_dma() */ + .dma = (pool->dma_pages[addr >> PAGE_SHIFT] & + ~XSK_NEXT_PG_CONTIG_MASK) + (addr & ~PAGE_MASK), + }; + + if (!pool->tx_metadata_len) + goto out; + + /* Same logic as in xp_raw_get_data() + xsk_buff_get_metadata() */ + meta = pool->addrs + addr - pool->tx_metadata_len; + if (unlikely(!xsk_buff_valid_tx_metadata(meta))) + goto out; + + ret.meta = meta; + +out: + return ret; +} +EXPORT_SYMBOL(xp_raw_get_ctx); -- 2.47.1