Commit e52fcb24 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller

bnx2x: uses build_skb() in receive path

bnx2x uses following formula to compute its rx_buf_sz :

dev->mtu + 2*L1_CACHE_BYTES + 14 + 8 + 8 + 2

Then core network adds NET_SKB_PAD and SKB_DATA_ALIGN(sizeof(struct
skb_shared_info))

Final allocated size for skb head on x86_64 (L1_CACHE_BYTES = 64,
MTU=1500) : 2112 bytes : SLUB/SLAB round this to 4096 bytes.

Since skb truesize is then bigger than SK_MEM_QUANTUM, we have lot of
false sharing because of mem_reclaim in UDP stack.

One possible way to half truesize is to reduce the need by 64 bytes
(2112 -> 2048 bytes)

Instead of allocating a full cache line at the end of packet for
alignment, we can use the fact that skb_shared_info sits at the end of
skb->head, and we can use this room, if we convert bnx2x to new
build_skb() infrastructure.

skb_shared_info will be initialized after hardware finished its
transfert, so we can eventually overwrite the final padding.

Using build_skb() also reduces cache line misses in the driver, since we
use cache hot skb instead of cold ones. Number of in-flight sk_buff
structures is lower, they are recycled while still hot.

Performance results :

(820.000 pps on a rx UDP monothread benchmark, instead of 720.000 pps)
Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
CC: Eilon Greenstein <eilong@broadcom.com>
CC: Ben Hutchings <bhutchings@solarflare.com>
CC: Tom Herbert <therbert@google.com>
CC: Jamal Hadi Salim <hadi@mojatatu.com>
CC: Stephen Hemminger <shemminger@vyatta.com>
CC: Thomas Graf <tgraf@infradead.org>
CC: Herbert Xu <herbert@gondor.apana.org.au>
CC: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Acked-by: default avatarEilon Greenstein <eilong@broadcom.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent b2b5ce9d
......@@ -293,8 +293,13 @@ enum {
#define FCOE_TXQ_IDX(bp) (MAX_ETH_TXQ_IDX(bp))
/* fast path */
/*
* This driver uses new build_skb() API :
* RX ring buffer contains pointer to kmalloc() data only,
* skb are built only after Hardware filled the frame.
*/
struct sw_rx_bd {
struct sk_buff *skb;
u8 *data;
DEFINE_DMA_UNMAP_ADDR(mapping);
};
......@@ -424,8 +429,8 @@ union host_hc_status_block {
struct bnx2x_agg_info {
/*
* First aggregation buffer is an skb, the following - are pages.
* We will preallocate the skbs for each aggregation when
* First aggregation buffer is a data buffer, the following - are pages.
* We will preallocate the data buffer for each aggregation when
* we open the interface and will replace the BD at the consumer
* with this one when we receive the TPA_START CQE in order to
* keep the Rx BD ring consistent.
......@@ -439,6 +444,7 @@ struct bnx2x_agg_info {
u16 parsing_flags;
u16 vlan_tag;
u16 len_on_bd;
u32 rxhash;
};
#define Q_STATS_OFFSET32(stat_name) \
......@@ -1187,10 +1193,20 @@ struct bnx2x {
#define ETH_MAX_JUMBO_PACKET_SIZE 9600
/* Max supported alignment is 256 (8 shift) */
#define BNX2X_RX_ALIGN_SHIFT ((L1_CACHE_SHIFT < 8) ? \
L1_CACHE_SHIFT : 8)
/* FW use 2 Cache lines Alignment for start packet and size */
#define BNX2X_FW_RX_ALIGN (2 << BNX2X_RX_ALIGN_SHIFT)
#define BNX2X_RX_ALIGN_SHIFT min(8, L1_CACHE_SHIFT)
/* FW uses 2 Cache lines Alignment for start packet and size
*
* We assume skb_build() uses sizeof(struct skb_shared_info) bytes
* at the end of skb->data, to avoid wasting a full cache line.
* This reduces memory use (skb->truesize).
*/
#define BNX2X_FW_RX_ALIGN_START (1UL << BNX2X_RX_ALIGN_SHIFT)
#define BNX2X_FW_RX_ALIGN_END \
max(1UL << BNX2X_RX_ALIGN_SHIFT, \
SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))
#define BNX2X_PXP_DRAM_ALIGN (BNX2X_RX_ALIGN_SHIFT - 5)
struct host_sp_status_block *def_status_blk;
......
......@@ -910,26 +910,27 @@ static inline int bnx2x_alloc_rx_sge(struct bnx2x *bp,
return 0;
}
static inline int bnx2x_alloc_rx_skb(struct bnx2x *bp,
static inline int bnx2x_alloc_rx_data(struct bnx2x *bp,
struct bnx2x_fastpath *fp, u16 index)
{
struct sk_buff *skb;
u8 *data;
struct sw_rx_bd *rx_buf = &fp->rx_buf_ring[index];
struct eth_rx_bd *rx_bd = &fp->rx_desc_ring[index];
dma_addr_t mapping;
skb = netdev_alloc_skb(bp->dev, fp->rx_buf_size);
if (unlikely(skb == NULL))
data = kmalloc(fp->rx_buf_size + NET_SKB_PAD, GFP_ATOMIC);
if (unlikely(data == NULL))
return -ENOMEM;
mapping = dma_map_single(&bp->pdev->dev, skb->data, fp->rx_buf_size,
mapping = dma_map_single(&bp->pdev->dev, data + NET_SKB_PAD,
fp->rx_buf_size,
DMA_FROM_DEVICE);
if (unlikely(dma_mapping_error(&bp->pdev->dev, mapping))) {
dev_kfree_skb_any(skb);
kfree(data);
return -ENOMEM;
}
rx_buf->skb = skb;
rx_buf->data = data;
dma_unmap_addr_set(rx_buf, mapping, mapping);
rx_bd->addr_hi = cpu_to_le32(U64_HI(mapping));
......@@ -938,12 +939,12 @@ static inline int bnx2x_alloc_rx_skb(struct bnx2x *bp,
return 0;
}
/* note that we are not allocating a new skb,
/* note that we are not allocating a new buffer,
* we are just moving one from cons to prod
* we are not creating a new mapping,
* so there is no need to check for dma_mapping_error().
*/
static inline void bnx2x_reuse_rx_skb(struct bnx2x_fastpath *fp,
static inline void bnx2x_reuse_rx_data(struct bnx2x_fastpath *fp,
u16 cons, u16 prod)
{
struct sw_rx_bd *cons_rx_buf = &fp->rx_buf_ring[cons];
......@@ -953,7 +954,7 @@ static inline void bnx2x_reuse_rx_skb(struct bnx2x_fastpath *fp,
dma_unmap_addr_set(prod_rx_buf, mapping,
dma_unmap_addr(cons_rx_buf, mapping));
prod_rx_buf->skb = cons_rx_buf->skb;
prod_rx_buf->data = cons_rx_buf->data;
*prod_bd = *cons_bd;
}
......@@ -1029,9 +1030,9 @@ static inline void bnx2x_free_tpa_pool(struct bnx2x *bp,
for (i = 0; i < last; i++) {
struct bnx2x_agg_info *tpa_info = &fp->tpa_info[i];
struct sw_rx_bd *first_buf = &tpa_info->first_buf;
struct sk_buff *skb = first_buf->skb;
u8 *data = first_buf->data;
if (skb == NULL) {
if (data == NULL) {
DP(NETIF_MSG_IFDOWN, "tpa bin %d empty on free\n", i);
continue;
}
......@@ -1039,8 +1040,8 @@ static inline void bnx2x_free_tpa_pool(struct bnx2x *bp,
dma_unmap_single(&bp->pdev->dev,
dma_unmap_addr(first_buf, mapping),
fp->rx_buf_size, DMA_FROM_DEVICE);
dev_kfree_skb(skb);
first_buf->skb = NULL;
kfree(data);
first_buf->data = NULL;
}
}
......@@ -1148,7 +1149,7 @@ static inline int bnx2x_alloc_rx_bds(struct bnx2x_fastpath *fp,
* fp->eth_q_stats.rx_skb_alloc_failed = 0
*/
for (i = 0; i < rx_ring_size; i++) {
if (bnx2x_alloc_rx_skb(bp, fp, ring_prod) < 0) {
if (bnx2x_alloc_rx_data(bp, fp, ring_prod) < 0) {
fp->eth_q_stats.rx_skb_alloc_failed++;
continue;
}
......
......@@ -1740,6 +1740,7 @@ static int bnx2x_run_loopback(struct bnx2x *bp, int loopback_mode)
struct sw_rx_bd *rx_buf;
u16 len;
int rc = -ENODEV;
u8 *data;
/* check the loopback mode */
switch (loopback_mode) {
......@@ -1865,10 +1866,9 @@ static int bnx2x_run_loopback(struct bnx2x *bp, int loopback_mode)
dma_sync_single_for_cpu(&bp->pdev->dev,
dma_unmap_addr(rx_buf, mapping),
fp_rx->rx_buf_size, DMA_FROM_DEVICE);
skb = rx_buf->skb;
skb_reserve(skb, cqe->fast_path_cqe.placement_offset);
data = rx_buf->data + NET_SKB_PAD + cqe->fast_path_cqe.placement_offset;
for (i = ETH_HLEN; i < pkt_size; i++)
if (*(skb->data + i) != (unsigned char) (i & 0xff))
if (*(data + i) != (unsigned char) (i & 0xff))
goto test_loopback_rx_exit;
rc = 0;
......
......@@ -2789,8 +2789,8 @@ static void bnx2x_pf_rx_q_prep(struct bnx2x *bp,
/* This should be a maximum number of data bytes that may be
* placed on the BD (not including paddings).
*/
rxq_init->buf_sz = fp->rx_buf_size - BNX2X_FW_RX_ALIGN -
IP_HEADER_ALIGNMENT_PADDING;
rxq_init->buf_sz = fp->rx_buf_size - BNX2X_FW_RX_ALIGN_START -
BNX2X_FW_RX_ALIGN_END - IP_HEADER_ALIGNMENT_PADDING;
rxq_init->cl_qzone_id = fp->cl_qzone_id;
rxq_init->tpa_agg_sz = tpa_agg_size;
......
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