Commit ee45fd92 authored by Jon Cooper's avatar Jon Cooper Committed by Ben Hutchings

sfc: Use TX PIO for sufficiently small packets

Sufficiently small linear packets can be copied into the PIO buffer
with a single call to memcpy_toio().  Non-linear packets require an
intermediate cache-line-sized buffer.

[bwh: I wrote the first version of this, but Jon did the hard work to
 handle non-linear packets.]
Signed-off-by: default avatarBen Hutchings <bhutchings@solarflare.com>
parent 0fe5565b
......@@ -315,6 +315,7 @@
#define ESF_DZ_TX_PIO_TYPE_WIDTH 1
#define ESF_DZ_TX_PIO_OPT_LBN 60
#define ESF_DZ_TX_PIO_OPT_WIDTH 3
#define ESE_DZ_TX_OPTION_DESC_PIO 1
#define ESF_DZ_TX_PIO_CONT_LBN 59
#define ESF_DZ_TX_PIO_CONT_WIDTH 1
#define ESF_DZ_TX_PIO_BYTE_CNT_LBN 32
......
......@@ -70,6 +70,7 @@ static const struct efx_sw_stat_desc efx_sw_stat_desc[] = {
EFX_ETHTOOL_UINT_TXQ_STAT(tso_long_headers),
EFX_ETHTOOL_UINT_TXQ_STAT(tso_packets),
EFX_ETHTOOL_UINT_TXQ_STAT(pushes),
EFX_ETHTOOL_UINT_TXQ_STAT(pio_packets),
EFX_ETHTOOL_ATOMIC_NIC_ERROR_STAT(rx_reset),
EFX_ETHTOOL_UINT_CHANNEL_STAT(rx_tobe_disc),
EFX_ETHTOOL_UINT_CHANNEL_STAT(rx_ip_hdr_chksum_err),
......
......@@ -212,6 +212,7 @@ struct efx_tx_buffer {
* blocks
* @tso_packets: Number of packets via the TSO xmit path
* @pushes: Number of times the TX push feature has been used
* @pio_packets: Number of times the TX PIO feature has been used
* @empty_read_count: If the completion path has seen the queue as empty
* and the transmission path has not yet checked this, the value of
* @read_count bitwise-added to %EFX_EMPTY_COUNT_VALID; otherwise 0.
......@@ -243,6 +244,7 @@ struct efx_tx_queue {
unsigned int tso_long_headers;
unsigned int tso_packets;
unsigned int pushes;
unsigned int pio_packets;
/* Members shared between paths and sometimes updated */
unsigned int empty_read_count ____cacheline_aligned_in_smp;
......
......@@ -183,6 +183,145 @@ static void efx_tx_maybe_stop_queue(struct efx_tx_queue *txq1)
}
}
#ifdef EFX_USE_PIO
struct efx_short_copy_buffer {
int used;
u8 buf[L1_CACHE_BYTES];
};
/* Copy to PIO, respecting that writes to PIO buffers must be dword aligned.
* Advances piobuf pointer. Leaves additional data in the copy buffer.
*/
static void efx_memcpy_toio_aligned(struct efx_nic *efx, u8 __iomem **piobuf,
u8 *data, int len,
struct efx_short_copy_buffer *copy_buf)
{
int block_len = len & ~(sizeof(copy_buf->buf) - 1);
memcpy_toio(*piobuf, data, block_len);
*piobuf += block_len;
len -= block_len;
if (len) {
data += block_len;
BUG_ON(copy_buf->used);
BUG_ON(len > sizeof(copy_buf->buf));
memcpy(copy_buf->buf, data, len);
copy_buf->used = len;
}
}
/* Copy to PIO, respecting dword alignment, popping data from copy buffer first.
* Advances piobuf pointer. Leaves additional data in the copy buffer.
*/
static void efx_memcpy_toio_aligned_cb(struct efx_nic *efx, u8 __iomem **piobuf,
u8 *data, int len,
struct efx_short_copy_buffer *copy_buf)
{
if (copy_buf->used) {
/* if the copy buffer is partially full, fill it up and write */
int copy_to_buf =
min_t(int, sizeof(copy_buf->buf) - copy_buf->used, len);
memcpy(copy_buf->buf + copy_buf->used, data, copy_to_buf);
copy_buf->used += copy_to_buf;
/* if we didn't fill it up then we're done for now */
if (copy_buf->used < sizeof(copy_buf->buf))
return;
memcpy_toio(*piobuf, copy_buf->buf, sizeof(copy_buf->buf));
*piobuf += sizeof(copy_buf->buf);
data += copy_to_buf;
len -= copy_to_buf;
copy_buf->used = 0;
}
efx_memcpy_toio_aligned(efx, piobuf, data, len, copy_buf);
}
static void efx_flush_copy_buffer(struct efx_nic *efx, u8 __iomem *piobuf,
struct efx_short_copy_buffer *copy_buf)
{
/* if there's anything in it, write the whole buffer, including junk */
if (copy_buf->used)
memcpy_toio(piobuf, copy_buf->buf, sizeof(copy_buf->buf));
}
/* Traverse skb structure and copy fragments in to PIO buffer.
* Advances piobuf pointer.
*/
static void efx_skb_copy_bits_to_pio(struct efx_nic *efx, struct sk_buff *skb,
u8 __iomem **piobuf,
struct efx_short_copy_buffer *copy_buf)
{
int i;
efx_memcpy_toio_aligned(efx, piobuf, skb->data, skb_headlen(skb),
copy_buf);
for (i = 0; i < skb_shinfo(skb)->nr_frags; ++i) {
skb_frag_t *f = &skb_shinfo(skb)->frags[i];
u8 *vaddr;
vaddr = kmap_atomic(skb_frag_page(f));
efx_memcpy_toio_aligned_cb(efx, piobuf, vaddr + f->page_offset,
skb_frag_size(f), copy_buf);
kunmap_atomic(vaddr);
}
EFX_BUG_ON_PARANOID(skb_shinfo(skb)->frag_list);
}
static struct efx_tx_buffer *
efx_enqueue_skb_pio(struct efx_tx_queue *tx_queue, struct sk_buff *skb)
{
struct efx_tx_buffer *buffer =
efx_tx_queue_get_insert_buffer(tx_queue);
u8 __iomem *piobuf = tx_queue->piobuf;
/* Copy to PIO buffer. Ensure the writes are padded to the end
* of a cache line, as this is required for write-combining to be
* effective on at least x86.
*/
if (skb_shinfo(skb)->nr_frags) {
/* The size of the copy buffer will ensure all writes
* are the size of a cache line.
*/
struct efx_short_copy_buffer copy_buf;
copy_buf.used = 0;
efx_skb_copy_bits_to_pio(tx_queue->efx, skb,
&piobuf, &copy_buf);
efx_flush_copy_buffer(tx_queue->efx, piobuf, &copy_buf);
} else {
/* Pad the write to the size of a cache line.
* We can do this because we know the skb_shared_info sruct is
* after the source, and the destination buffer is big enough.
*/
BUILD_BUG_ON(L1_CACHE_BYTES >
SKB_DATA_ALIGN(sizeof(struct skb_shared_info)));
memcpy_toio(tx_queue->piobuf, skb->data,
ALIGN(skb->len, L1_CACHE_BYTES));
}
EFX_POPULATE_QWORD_5(buffer->option,
ESF_DZ_TX_DESC_IS_OPT, 1,
ESF_DZ_TX_OPTION_TYPE, ESE_DZ_TX_OPTION_DESC_PIO,
ESF_DZ_TX_PIO_CONT, 0,
ESF_DZ_TX_PIO_BYTE_CNT, skb->len,
ESF_DZ_TX_PIO_BUF_ADDR,
tx_queue->piobuf_offset);
++tx_queue->pio_packets;
++tx_queue->insert_count;
return buffer;
}
#endif /* EFX_USE_PIO */
/*
* Add a socket buffer to a TX queue
*
......@@ -227,6 +366,17 @@ netdev_tx_t efx_enqueue_skb(struct efx_tx_queue *tx_queue, struct sk_buff *skb)
return NETDEV_TX_OK;
}
/* Consider using PIO for short packets */
#ifdef EFX_USE_PIO
if (skb->len <= efx_piobuf_size && tx_queue->piobuf &&
efx_nic_tx_is_empty(tx_queue) &&
efx_nic_tx_is_empty(efx_tx_queue_partner(tx_queue))) {
buffer = efx_enqueue_skb_pio(tx_queue, skb);
dma_flags = EFX_TX_BUF_OPTION;
goto finish_packet;
}
#endif
/* Map for DMA. Use dma_map_single rather than dma_map_page
* since this is more efficient on machines with sparse
* memory.
......@@ -279,6 +429,7 @@ netdev_tx_t efx_enqueue_skb(struct efx_tx_queue *tx_queue, struct sk_buff *skb)
}
/* Transfer ownership of the skb to the final buffer */
finish_packet:
buffer->skb = skb;
buffer->flags = EFX_TX_BUF_SKB | dma_flags;
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment