e1000: Buffer optimizations for small MTU

Remove multi-descriptor support from legacy recieve path

Add memory usage efficiency by using more correct size descriptors for
small MTU sizes and optimize using LPE for <= 1522 byte frame sizes

An extra performance fix that effected our TCP window size growth
as a receiver.  Set our initial buffer to be 128 bytes instead of 256
to prevent over-socket charge when truesize is computed in the stack.
old way: truesize = 256 + l1 = 256 + 1460 = 1716
new way: truesize = 128 + l1 = 128 + 1460 = 1588
The magic value that we can't cross is 1648.


Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Auke Kok <auke-jan.h.kok@intel.com>
Signed-off-by: John Ronciak <john.ronciak@intel.com>

2 files changed, 52 insertions, 37 deletions

diff --git a/drivers/net/e1000/e1000.h b/drivers/net/e1000/e1000.h
index 764808f3702e..2dfabdb29e7b 100644
--- a/drivers/net/e1000/e1000.h
+++ b/drivers/net/e1000/e1000.h
@@ -114,6 +114,8 @@ struct e1000_adapter;
 /* Supported Rx Buffer Sizes */
 #define E1000_RXBUFFER_128   128    /* Used for packet split */
 #define E1000_RXBUFFER_256   256    /* Used for packet split */
+#define E1000_RXBUFFER_512   512
+#define E1000_RXBUFFER_1024  1024
 #define E1000_RXBUFFER_2048  2048
 #define E1000_RXBUFFER_4096  4096
 #define E1000_RXBUFFER_8192  8192
diff --git a/drivers/net/e1000/e1000_main.c b/drivers/net/e1000/e1000_main.c
index 6d7ba0bb233a..f604a1dea399 100644
--- a/drivers/net/e1000/e1000_main.c
+++ b/drivers/net/e1000/e1000_main.c
@@ -972,8 +972,8 @@ e1000_sw_init(struct e1000_adapter *adapter)
 
         pci_read_config_word(pdev, PCI_COMMAND, &hw->pci_cmd_word);
 
-        adapter->rx_buffer_len = E1000_RXBUFFER_2048;
-        adapter->rx_ps_bsize0 = E1000_RXBUFFER_256;
+        adapter->rx_buffer_len = MAXIMUM_ETHERNET_FRAME_SIZE;
+        adapter->rx_ps_bsize0 = E1000_RXBUFFER_128;
         hw->max_frame_size = netdev->mtu +
                              ENET_HEADER_SIZE + ETHERNET_FCS_SIZE;
         hw->min_frame_size = MINIMUM_ETHERNET_FRAME_SIZE;
@@ -1599,14 +1599,21 @@ e1000_setup_rctl(struct e1000_adapter *adapter)
                 rctl |= E1000_RCTL_LPE;
 
         /* Setup buffer sizes */
-        if (adapter->hw.mac_type >= e1000_82571) {
-                /* We can now specify buffers in 1K increments.
-                 * BSIZE and BSEX are ignored in this case. */
-                rctl |= adapter->rx_buffer_len << 0x11;
-        } else {
-                rctl &= ~E1000_RCTL_SZ_4096;
-                rctl |= E1000_RCTL_BSEX; 
-                switch (adapter->rx_buffer_len) {
+        rctl &= ~E1000_RCTL_SZ_4096;
+        rctl |= E1000_RCTL_BSEX;
+        switch (adapter->rx_buffer_len) {
+                case E1000_RXBUFFER_256:
+                        rctl |= E1000_RCTL_SZ_256;
+                        rctl &= ~E1000_RCTL_BSEX;
+                        break;
+                case E1000_RXBUFFER_512:
+                        rctl |= E1000_RCTL_SZ_512;
+                        rctl &= ~E1000_RCTL_BSEX;
+                        break;
+                case E1000_RXBUFFER_1024:
+                        rctl |= E1000_RCTL_SZ_1024;
+                        rctl &= ~E1000_RCTL_BSEX;
+                        break;
                 case E1000_RXBUFFER_2048:
                 default:
                         rctl |= E1000_RCTL_SZ_2048;
@@ -1621,7 +1628,6 @@ e1000_setup_rctl(struct e1000_adapter *adapter)
                 case E1000_RXBUFFER_16384:
                         rctl |= E1000_RCTL_SZ_16384;
                         break;
-                }
         }
 
 #ifndef CONFIG_E1000_DISABLE_PACKET_SPLIT
@@ -2982,8 +2988,7 @@ e1000_change_mtu(struct net_device *netdev, int new_mtu)
 
         /* Adapter-specific max frame size limits. */
         switch (adapter->hw.mac_type) {
-        case e1000_82542_rev2_0:
-        case e1000_82542_rev2_1:
+        case e1000_undefined ... e1000_82542_rev2_1:
                 if (max_frame > MAXIMUM_ETHERNET_FRAME_SIZE) {
                         DPRINTK(PROBE, ERR, "Jumbo Frames not supported.\n");
                         return -EINVAL;
@@ -3017,27 +3022,32 @@ e1000_change_mtu(struct net_device *netdev, int new_mtu)
                 break;
         }
 
-
-        if (adapter->hw.mac_type > e1000_82547_rev_2) {
-                adapter->rx_buffer_len = max_frame;
-                E1000_ROUNDUP(adapter->rx_buffer_len, 1024);
-        } else {
-                if(unlikely((adapter->hw.mac_type < e1000_82543) &&
-                   (max_frame > MAXIMUM_ETHERNET_FRAME_SIZE))) {
-                        DPRINTK(PROBE, ERR, "Jumbo Frames not supported "
-                                            "on 82542\n");
-                        return -EINVAL;
-                } else {
-                        if(max_frame <= E1000_RXBUFFER_2048)
-                                adapter->rx_buffer_len = E1000_RXBUFFER_2048;
-                        else if(max_frame <= E1000_RXBUFFER_4096)
-                                adapter->rx_buffer_len = E1000_RXBUFFER_4096;
-                        else if(max_frame <= E1000_RXBUFFER_8192)
-                                adapter->rx_buffer_len = E1000_RXBUFFER_8192;
-                        else if(max_frame <= E1000_RXBUFFER_16384)
-                                adapter->rx_buffer_len = E1000_RXBUFFER_16384;
-                }
-        }
+        /* NOTE: dev_alloc_skb reserves 16 bytes, and typically NET_IP_ALIGN
+         * means we reserve 2 more, this pushes us to allocate from the next
+         * larger slab size
+         * i.e. RXBUFFER_2048 --> size-4096 slab */
+
+        if (max_frame <= E1000_RXBUFFER_256)
+                adapter->rx_buffer_len = E1000_RXBUFFER_256;
+        else if (max_frame <= E1000_RXBUFFER_512)
+                adapter->rx_buffer_len = E1000_RXBUFFER_512;
+        else if (max_frame <= E1000_RXBUFFER_1024)
+                adapter->rx_buffer_len = E1000_RXBUFFER_1024;
+        else if (max_frame <= E1000_RXBUFFER_2048)
+                adapter->rx_buffer_len = E1000_RXBUFFER_2048;
+        else if (max_frame <= E1000_RXBUFFER_4096)
+                adapter->rx_buffer_len = E1000_RXBUFFER_4096;
+        else if (max_frame <= E1000_RXBUFFER_8192)
+                adapter->rx_buffer_len = E1000_RXBUFFER_8192;
+        else if (max_frame <= E1000_RXBUFFER_16384)
+                adapter->rx_buffer_len = E1000_RXBUFFER_16384;
+
+        /* adjust allocation if LPE protects us, and we aren't using SBP */
+#define MAXIMUM_ETHERNET_VLAN_SIZE 1522
+        if (!adapter->hw.tbi_compatibility_on &&
+            ((max_frame == MAXIMUM_ETHERNET_FRAME_SIZE) ||
+             (max_frame == MAXIMUM_ETHERNET_VLAN_SIZE)))
+                adapter->rx_buffer_len = MAXIMUM_ETHERNET_VLAN_SIZE;
 
         netdev->mtu = new_mtu;
 
@@ -3568,10 +3578,12 @@ e1000_clean_rx_irq(struct e1000_adapter *adapter,
                                                        flags);
                                 length--;
                         } else {
-                                dev_kfree_skb_irq(skb);
+                                /* recycle */
+                                buffer_info->skb = skb;
                                 goto next_desc;
                         }
-                }
+                } else
+                        skb_put(skb, length);
 
                 /* code added for copybreak, this should improve
                  * performance for small packets with large amounts
@@ -3676,6 +3688,7 @@ e1000_clean_rx_irq_ps(struct e1000_adapter *adapter,
         i = rx_ring->next_to_clean;
         rx_desc = E1000_RX_DESC_PS(*rx_ring, i);
         staterr = le32_to_cpu(rx_desc->wb.middle.status_error);
+        buffer_info = &rx_ring->buffer_info[i];
 
         while (staterr & E1000_RXD_STAT_DD) {
                 buffer_info = &rx_ring->buffer_info[i];
@@ -3736,7 +3749,7 @@ e1000_clean_rx_irq_ps(struct e1000_adapter *adapter,
 
                 /* page alloc/put takes too long and effects small packet
                  * throughput, so unsplit small packets and save the alloc/put*/
-                if (l1 && ((length + l1) < E1000_CB_LENGTH)) {
+                if (l1 && ((length + l1) <= adapter->rx_ps_bsize0)) {
                         u8 *vaddr;
                         /* there is no documentation about how to call 
                          * kmap_atomic, so we can't hold the mapping