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Commit 8d4057a9 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
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tg3: provide frags as skb head 



This patch converts tg3 driver, one of our reference drivers, to use new
build_skb() api in frag mode.

Instead of using kmalloc() to allocate the memory block that will be
used by build_skb() as skb->head, we use a page fragment.

This is a followup of patch "net: allow skb->head to be a page fragment"

This allows GRO, TCP coalescing, and splice() to be more efficient.

Incidentally, this also removes SLUB slow path contention in kfree()

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Cc: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Maciej Żenczykowski <maze@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Tom Herbert <therbert@google.com>
Cc: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Cc: Ben Hutchings <bhutchings@solarflare.com>
Cc: Matt Carlson <mcarlson@broadcom.com>
Cc: Michael Chan <mchan@broadcom.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent d3836f21

drivers/net/ethernet/broadcom/tg3.c

+64 −10
Original line number Diff line number Diff line
@@ -195,6 +195,15 @@ static inline void _tg3_flag_clear(enum TG3_FLAGS flag, unsigned long *bits) 
#define TG3_RX_OFFSET(tp)	(NET_SKB_PAD)

#endif



/* This driver uses the new build_skb() API providing a frag as skb->head

 * This strategy permits better GRO aggregation, better TCP coalescing, and

 * better splice() implementation (avoids a copy from head to a page), at

 * minimal memory cost.

 * In this 2048 bytes block, we have enough room to store the MTU=1500 frame

 * and the struct skb_shared_info.

 */

#define TG3_FRAGSIZE 2048



/* minimum number of free TX descriptors required to wake up TX process */

#define TG3_TX_WAKEUP_THRESH(tnapi)		((tnapi)->tx_pending / 4)

#define TG3_TX_BD_DMA_MAX_2K		2048
@@ -5617,17 +5626,48 @@ static void tg3_tx(struct tg3_napi *tnapi) 
	}

}



static void *tg3_frag_alloc(struct tg3_rx_prodring_set *tpr)

{

	void *data;



	if (tpr->rx_page_size < TG3_FRAGSIZE) {

		struct page *page = alloc_page(GFP_ATOMIC);



		if (!page)

			return NULL;

		atomic_add((PAGE_SIZE / TG3_FRAGSIZE) - 1, &page->_count);

		tpr->rx_page_addr = page_address(page);

		tpr->rx_page_size = PAGE_SIZE;

	}

	data = tpr->rx_page_addr;

	tpr->rx_page_addr += TG3_FRAGSIZE;

	tpr->rx_page_size -= TG3_FRAGSIZE;

	return data;

}



static void tg3_frag_free(bool is_frag, void *data)

{

	if (is_frag)

		put_page(virt_to_head_page(data));

	else

		kfree(data);

}



static void tg3_rx_data_free(struct tg3 *tp, struct ring_info *ri, u32 map_sz)

{

	unsigned int skb_size = SKB_DATA_ALIGN(map_sz + TG3_RX_OFFSET(tp)) +

		   SKB_DATA_ALIGN(sizeof(struct skb_shared_info));



	if (!ri->data)

		return;



	pci_unmap_single(tp->pdev, dma_unmap_addr(ri, mapping),

			 map_sz, PCI_DMA_FROMDEVICE);

	kfree(ri->data);

	tg3_frag_free(skb_size <= TG3_FRAGSIZE, ri->data);

	ri->data = NULL;

}





/* Returns size of skb allocated or < 0 on error.

 *

 * We only need to fill in the address because the other members
@@ -5640,7 +5680,8 @@ static void tg3_rx_data_free(struct tg3 *tp, struct ring_info *ri, u32 map_sz) 
 * (to fetch the error flags, vlan tag, checksum, and opaque cookie).

 */

static int tg3_alloc_rx_data(struct tg3 *tp, struct tg3_rx_prodring_set *tpr,

			    u32 opaque_key, u32 dest_idx_unmasked)

			     u32 opaque_key, u32 dest_idx_unmasked,

			     unsigned int *frag_size)

{

	struct tg3_rx_buffer_desc *desc;

	struct ring_info *map;
@@ -5675,7 +5716,13 @@ static int tg3_alloc_rx_data(struct tg3 *tp, struct tg3_rx_prodring_set *tpr, 
	 */

	skb_size = SKB_DATA_ALIGN(data_size + TG3_RX_OFFSET(tp)) +

		   SKB_DATA_ALIGN(sizeof(struct skb_shared_info));

	if (skb_size <= TG3_FRAGSIZE) {

		data = tg3_frag_alloc(tpr);

		*frag_size = TG3_FRAGSIZE;

	} else {

		data = kmalloc(skb_size, GFP_ATOMIC);

		*frag_size = 0;

	}

	if (!data)

		return -ENOMEM;
@@ -5683,8 +5730,8 @@ static int tg3_alloc_rx_data(struct tg3 *tp, struct tg3_rx_prodring_set *tpr, 
				 data + TG3_RX_OFFSET(tp),

				 data_size,

				 PCI_DMA_FROMDEVICE);

	if (pci_dma_mapping_error(tp->pdev, mapping)) {

		kfree(data);

	if (unlikely(pci_dma_mapping_error(tp->pdev, mapping))) {

		tg3_frag_free(skb_size <= TG3_FRAGSIZE, data);

		return -EIO;

	}
@@ -5835,18 +5882,19 @@ static int tg3_rx(struct tg3_napi *tnapi, int budget) 


		if (len > TG3_RX_COPY_THRESH(tp)) {

			int skb_size;

			unsigned int frag_size;



			skb_size = tg3_alloc_rx_data(tp, tpr, opaque_key,

						    *post_ptr);

						    *post_ptr, &frag_size);

			if (skb_size < 0)

				goto drop_it;



			pci_unmap_single(tp->pdev, dma_addr, skb_size,

					 PCI_DMA_FROMDEVICE);



			skb = build_skb(data, 0);

			skb = build_skb(data, frag_size);

			if (!skb) {

				kfree(data);

				tg3_frag_free(frag_size != 0, data);

				goto drop_it_no_recycle;

			}

			skb_reserve(skb, TG3_RX_OFFSET(tp));
@@ -7279,7 +7327,10 @@ static int tg3_rx_prodring_alloc(struct tg3 *tp, 


	/* Now allocate fresh SKBs for each rx ring. */

	for (i = 0; i < tp->rx_pending; i++) {

		if (tg3_alloc_rx_data(tp, tpr, RXD_OPAQUE_RING_STD, i) < 0) {

		unsigned int frag_size;



		if (tg3_alloc_rx_data(tp, tpr, RXD_OPAQUE_RING_STD, i,

				      &frag_size) < 0) {

			netdev_warn(tp->dev,

				    "Using a smaller RX standard ring. Only "

				    "%d out of %d buffers were allocated "
@@ -7311,7 +7362,10 @@ static int tg3_rx_prodring_alloc(struct tg3 *tp, 
	}



	for (i = 0; i < tp->rx_jumbo_pending; i++) {

		if (tg3_alloc_rx_data(tp, tpr, RXD_OPAQUE_RING_JUMBO, i) < 0) {

		unsigned int frag_size;



		if (tg3_alloc_rx_data(tp, tpr, RXD_OPAQUE_RING_JUMBO, i,

				      &frag_size) < 0) {

			netdev_warn(tp->dev,

				    "Using a smaller RX jumbo ring. Only %d "

				    "out of %d buffers were allocated "

drivers/net/ethernet/broadcom/tg3.h

+2 −0
Original line number Diff line number Diff line
@@ -2815,6 +2815,8 @@ struct tg3_rx_prodring_set { 
	struct ring_info		*rx_jmb_buffers;

	dma_addr_t			rx_std_mapping;

	dma_addr_t			rx_jmb_mapping;

	void				*rx_page_addr;

	unsigned int			rx_page_size;

};



#define TG3_IRQ_MAX_VECS_RSS		5