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i40e/i40evf: Update code to better handle incrementing page count
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Update the driver code so that we do bulk updates of the page reference
count instead of just incrementing it by one reference at a time.  The
advantage to doing this is that we cut down on atomic operations and
this in turn should give us a slight improvement in cycles per packet.
In addition if we eventually move this over to using build_skb the gains
will be more noticeable.

I also found and fixed a store forwarding stall from where we were
assigning "*new_buff = *old_buff".  By breaking it up into individual
copies we can avoid this and as a result the performance is slightly
improved.

Change-ID: I1d3880dece4133eca3c32423b04a5467321ccc52
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
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Alexander Duyck authored and Jeff Kirsher committed Mar 27, 2017
1 parent 402a5bc commit 1793668
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Showing 4 changed files with 48 additions and 15 deletions.
25 changes: 18 additions & 7 deletions drivers/net/ethernet/intel/i40e/i40e_txrx.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1154,7 +1154,7 @@ void i40e_clean_rx_ring(struct i40e_ring *rx_ring)
PAGE_SIZE,
DMA_FROM_DEVICE,
I40E_RX_DMA_ATTR);
__free_pages(rx_bi->page, 0);
__page_frag_cache_drain(rx_bi->page, rx_bi->pagecnt_bias);

rx_bi->page = NULL;
rx_bi->page_offset = 0;
Expand Down Expand Up @@ -1299,6 +1299,7 @@ static bool i40e_alloc_mapped_page(struct i40e_ring *rx_ring,
bi->dma = dma;
bi->page = page;
bi->page_offset = 0;
bi->pagecnt_bias = 1;

return true;
}
Expand Down Expand Up @@ -1604,7 +1605,10 @@ static void i40e_reuse_rx_page(struct i40e_ring *rx_ring,
rx_ring->next_to_alloc = (nta < rx_ring->count) ? nta : 0;

/* transfer page from old buffer to new buffer */
*new_buff = *old_buff;
new_buff->dma = old_buff->dma;
new_buff->page = old_buff->page;
new_buff->page_offset = old_buff->page_offset;
new_buff->pagecnt_bias = old_buff->pagecnt_bias;
}

/**
Expand Down Expand Up @@ -1656,14 +1660,15 @@ static bool i40e_can_reuse_rx_page(struct i40e_rx_buffer *rx_buffer,
#if (PAGE_SIZE >= 8192)
unsigned int last_offset = PAGE_SIZE - I40E_RXBUFFER_2048;
#endif
unsigned int pagecnt_bias = rx_buffer->pagecnt_bias--;

/* Is any reuse possible? */
if (unlikely(!i40e_page_is_reusable(page)))
return false;

#if (PAGE_SIZE < 8192)
/* if we are only owner of page we can reuse it */
if (unlikely(page_count(page) != 1))
if (unlikely(page_count(page) != pagecnt_bias))
return false;

/* flip page offset to other buffer */
Expand All @@ -1676,9 +1681,14 @@ static bool i40e_can_reuse_rx_page(struct i40e_rx_buffer *rx_buffer,
return false;
#endif

/* Inc ref count on page before passing it up to the stack */
get_page(page);

/* If we have drained the page fragment pool we need to update
* the pagecnt_bias and page count so that we fully restock the
* number of references the driver holds.
*/
if (unlikely(pagecnt_bias == 1)) {
page_ref_add(page, USHRT_MAX);
rx_buffer->pagecnt_bias = USHRT_MAX;
}
return true;
}

Expand Down Expand Up @@ -1725,7 +1735,6 @@ static bool i40e_add_rx_frag(struct i40e_ring *rx_ring,
return true;

/* this page cannot be reused so discard it */
__free_pages(page, 0);
return false;
}

Expand Down Expand Up @@ -1819,6 +1828,8 @@ struct sk_buff *i40e_fetch_rx_buffer(struct i40e_ring *rx_ring,
/* we are not reusing the buffer so unmap it */
dma_unmap_page_attrs(rx_ring->dev, rx_buffer->dma, PAGE_SIZE,
DMA_FROM_DEVICE, I40E_RX_DMA_ATTR);
__page_frag_cache_drain(rx_buffer->page,
rx_buffer->pagecnt_bias);
}

/* clear contents of buffer_info */
Expand Down
7 changes: 6 additions & 1 deletion drivers/net/ethernet/intel/i40e/i40e_txrx.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -258,7 +258,12 @@ struct i40e_tx_buffer {
struct i40e_rx_buffer {
dma_addr_t dma;
struct page *page;
unsigned int page_offset;
#if (BITS_PER_LONG > 32) || (PAGE_SIZE >= 65536)
__u32 page_offset;
#else
__u16 page_offset;
#endif
__u16 pagecnt_bias;
};

struct i40e_queue_stats {
Expand Down
24 changes: 18 additions & 6 deletions drivers/net/ethernet/intel/i40evf/i40e_txrx.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -526,7 +526,7 @@ void i40evf_clean_rx_ring(struct i40e_ring *rx_ring)
PAGE_SIZE,
DMA_FROM_DEVICE,
I40E_RX_DMA_ATTR);
__free_pages(rx_bi->page, 0);
__page_frag_cache_drain(rx_bi->page, rx_bi->pagecnt_bias);

rx_bi->page = NULL;
rx_bi->page_offset = 0;
Expand Down Expand Up @@ -671,6 +671,7 @@ static bool i40e_alloc_mapped_page(struct i40e_ring *rx_ring,
bi->dma = dma;
bi->page = page;
bi->page_offset = 0;
bi->pagecnt_bias = 1;

return true;
}
Expand Down Expand Up @@ -966,7 +967,10 @@ static void i40e_reuse_rx_page(struct i40e_ring *rx_ring,
rx_ring->next_to_alloc = (nta < rx_ring->count) ? nta : 0;

/* transfer page from old buffer to new buffer */
*new_buff = *old_buff;
new_buff->dma = old_buff->dma;
new_buff->page = old_buff->page;
new_buff->page_offset = old_buff->page_offset;
new_buff->pagecnt_bias = old_buff->pagecnt_bias;
}

/**
Expand Down Expand Up @@ -1018,14 +1022,15 @@ static bool i40e_can_reuse_rx_page(struct i40e_rx_buffer *rx_buffer,
#if (PAGE_SIZE >= 8192)
unsigned int last_offset = PAGE_SIZE - I40E_RXBUFFER_2048;
#endif
unsigned int pagecnt_bias = rx_buffer->pagecnt_bias--;

/* Is any reuse possible? */
if (unlikely(!i40e_page_is_reusable(page)))
return false;

#if (PAGE_SIZE < 8192)
/* if we are only owner of page we can reuse it */
if (unlikely(page_count(page) != 1))
if (unlikely(page_count(page) != pagecnt_bias))
return false;

/* flip page offset to other buffer */
Expand All @@ -1038,8 +1043,14 @@ static bool i40e_can_reuse_rx_page(struct i40e_rx_buffer *rx_buffer,
return false;
#endif

/* Inc ref count on page before passing it up to the stack */
get_page(page);
/* If we have drained the page fragment pool we need to update
* the pagecnt_bias and page count so that we fully restock the
* number of references the driver holds.
*/
if (unlikely(pagecnt_bias == 1)) {
page_ref_add(page, USHRT_MAX);
rx_buffer->pagecnt_bias = USHRT_MAX;
}

return true;
}
Expand Down Expand Up @@ -1087,7 +1098,6 @@ static bool i40e_add_rx_frag(struct i40e_ring *rx_ring,
return true;

/* this page cannot be reused so discard it */
__free_pages(page, 0);
return false;
}

Expand Down Expand Up @@ -1181,6 +1191,8 @@ struct sk_buff *i40evf_fetch_rx_buffer(struct i40e_ring *rx_ring,
/* we are not reusing the buffer so unmap it */
dma_unmap_page_attrs(rx_ring->dev, rx_buffer->dma, PAGE_SIZE,
DMA_FROM_DEVICE, I40E_RX_DMA_ATTR);
__page_frag_cache_drain(rx_buffer->page,
rx_buffer->pagecnt_bias);
}

/* clear contents of buffer_info */
Expand Down
7 changes: 6 additions & 1 deletion drivers/net/ethernet/intel/i40evf/i40e_txrx.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -244,7 +244,12 @@ struct i40e_tx_buffer {
struct i40e_rx_buffer {
dma_addr_t dma;
struct page *page;
unsigned int page_offset;
#if (BITS_PER_LONG > 32) || (PAGE_SIZE >= 65536)
__u32 page_offset;
#else
__u16 page_offset;
#endif
__u16 pagecnt_bias;
};

struct i40e_queue_stats {
Expand Down

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