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| author | Christophe Leroy <christophe.leroy@c-s.fr> | 2016-09-09 14:26:23 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2016-09-10 21:17:13 -0700 |
| commit | 070e1f01827c658b76bef6e3fa79046b4e4a7693 (patch) | |
| tree | b4689b5004ea96ae0ca37b8ed7435508eb6b4be5 /drivers | |
| parent | 8572763af48728561f8bf708b6c0ea9f4db5929e (diff) | |
| download | linux-stable-070e1f01827c658b76bef6e3fa79046b4e4a7693.tar.gz linux-stable-070e1f01827c658b76bef6e3fa79046b4e4a7693.tar.bz2 linux-stable-070e1f01827c658b76bef6e3fa79046b4e4a7693.zip | |
net: fs_enet: don't unmap DMA when packet len is below copybreak
When the length of the packet is below the defined copybreak limit,
the received packet is copied into a newly allocated skb in order
to reuse the skb. This is only interesting if it allow us to avoid
a new DMA mapping. We shall therefore not DMA unmap and remap the
skb->data. Instead, we invalidate the cache
with dma_sync_single_for_cpu() once the received data has been
copied into the new skb.
The following measures have been obtained on a mpc885 running at 132Mhz.
Measurement is done using the timebase with packets sent to the target
with 'ping -s 1' (packet len is 60):
* Without this patch: 182 TB ticks
* With this patch: 143 TB ticks
As a comparison, if we set the copybreak limit to 0, then we get
148 TB ticks. It means that without this patch, duration is even
worse when copying received data to a new skb instead of
allocating a new skb for next packet to be received
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c | 36 |
1 files changed, 20 insertions, 16 deletions
diff --git a/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c b/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c index 37574a97a61c..f2a60cd1feed 100644 --- a/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c +++ b/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c @@ -226,21 +226,10 @@ static int fs_enet_napi(struct napi_struct *napi, int budget) if (sc & BD_ENET_RX_OV) fep->stats.rx_crc_errors++; - skb = fep->rx_skbuff[curidx]; - - dma_unmap_single(fep->dev, CBDR_BUFADDR(bdp), - L1_CACHE_ALIGN(PKT_MAXBUF_SIZE), - DMA_FROM_DEVICE); - - skbn = skb; - + skbn = fep->rx_skbuff[curidx]; } else { skb = fep->rx_skbuff[curidx]; - dma_unmap_single(fep->dev, CBDR_BUFADDR(bdp), - L1_CACHE_ALIGN(PKT_MAXBUF_SIZE), - DMA_FROM_DEVICE); - /* * Process the incoming frame. */ @@ -256,12 +245,30 @@ static int fs_enet_napi(struct napi_struct *napi, int budget) skb_copy_from_linear_data(skb, skbn->data, pkt_len); swap(skb, skbn); + dma_sync_single_for_cpu(fep->dev, + CBDR_BUFADDR(bdp), + L1_CACHE_ALIGN(pkt_len), + DMA_FROM_DEVICE); } } else { skbn = netdev_alloc_skb(dev, ENET_RX_FRSIZE); - if (skbn) + if (skbn) { + dma_addr_t dma; + skb_align(skbn, ENET_RX_ALIGN); + + dma_unmap_single(fep->dev, + CBDR_BUFADDR(bdp), + L1_CACHE_ALIGN(PKT_MAXBUF_SIZE), + DMA_FROM_DEVICE); + + dma = dma_map_single(fep->dev, + skbn->data, + L1_CACHE_ALIGN(PKT_MAXBUF_SIZE), + DMA_FROM_DEVICE); + CBDW_BUFADDR(bdp, dma); + } } if (skbn != NULL) { @@ -276,9 +283,6 @@ static int fs_enet_napi(struct napi_struct *napi, int budget) } fep->rx_skbuff[curidx] = skbn; - CBDW_BUFADDR(bdp, dma_map_single(fep->dev, skbn->data, - L1_CACHE_ALIGN(PKT_MAXBUF_SIZE), - DMA_FROM_DEVICE)); CBDW_DATLEN(bdp, 0); CBDW_SC(bdp, (sc & ~BD_ENET_RX_STATS) | BD_ENET_RX_EMPTY); |