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Commit 60b86665 authored by stephen hemminger's avatar stephen hemminger Committed by David S. Miller
Browse files

netvsc: optimize calculation of number of slots 



Speed up transmit check for fragmented packets by using existing
macros to compute number of pages, and eliminate loop since
skb fragments each take a page. Number of slots is also unsigned.

Signed-off-by: default avatarStephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent e073782a

drivers/net/hyperv/netvsc_drv.c

+10 −33
Original line number Diff line number Diff line
@@ -345,34 +345,14 @@ static u32 init_page_array(void *hdr, u32 len, struct sk_buff *skb, 
	return slots_used;

}



static int count_skb_frag_slots(struct sk_buff *skb)

{

	int i, frags = skb_shinfo(skb)->nr_frags;

	int pages = 0;



	for (i = 0; i < frags; i++) {

		skb_frag_t *frag = skb_shinfo(skb)->frags + i;

		unsigned long size = skb_frag_size(frag);

		unsigned long offset = frag->page_offset;



		/* Skip unused frames from start of page */

		offset &= ~PAGE_MASK;

		pages += PFN_UP(offset + size);

	}

	return pages;

}



static int netvsc_get_slots(struct sk_buff *skb)

/* Estimate number of page buffers neede to transmit

 * Need at most 2 for RNDIS header plus skb body and fragments.

 */

static unsigned int netvsc_get_slots(const struct sk_buff *skb)

{

	char *data = skb->data;

	unsigned int offset = offset_in_page(data);

	unsigned int len = skb_headlen(skb);

	int slots;

	int frag_slots;



	slots = DIV_ROUND_UP(offset + len, PAGE_SIZE);

	frag_slots = count_skb_frag_slots(skb);

	return slots + frag_slots;

	return PFN_UP(offset_in_page(skb->data) + skb_headlen(skb))

		+ skb_shinfo(skb)->nr_frags

		+ 2;

}



static u32 net_checksum_info(struct sk_buff *skb)
@@ -410,21 +390,18 @@ static int netvsc_start_xmit(struct sk_buff *skb, struct net_device *net) 
	struct hv_page_buffer page_buf[MAX_PAGE_BUFFER_COUNT];

	struct hv_page_buffer *pb = page_buf;



	/* We will atmost need two pages to describe the rndis

	 * header. We can only transmit MAX_PAGE_BUFFER_COUNT number

	/* We can only transmit MAX_PAGE_BUFFER_COUNT number

	 * of pages in a single packet. If skb is scattered around

	 * more pages we try linearizing it.

	 */



	num_data_pgs = netvsc_get_slots(skb) + 2;



	num_data_pgs = netvsc_get_slots(skb);

	if (unlikely(num_data_pgs > MAX_PAGE_BUFFER_COUNT)) {

		++net_device_ctx->eth_stats.tx_scattered;



		if (skb_linearize(skb))

			goto no_memory;



		num_data_pgs = netvsc_get_slots(skb) + 2;

		num_data_pgs = netvsc_get_slots(skb);

		if (num_data_pgs > MAX_PAGE_BUFFER_COUNT) {

			++net_device_ctx->eth_stats.tx_too_big;

			goto drop;