A bunch of netmap fixes:

USERSPACE:
1. add support for devices with different number of rx and tx queues;

2. add better support for zero-copy operation, adding an extra field
   to the netmap ring to indicate how many buffers we have already processed
   but not yet released (with help from Eddie Kohler);

3. The two changes above unfortunately require an API change, so while
   at it add a version field and some spares to the ioctl() argument
   to help detect mismatches.

4. update the manual page for the two changes above;

5. update sample applications in tools/tools/netmap

KERNEL:

1. simplify the internal structures moving the global wait queues
   to the 'struct netmap_adapter';

2. simplify the functions that map kring<->nic ring indexes

3. normalize device-specific code, helps mainteinance;

4. start exploring the impact of micro-optimizations (prefetch etc.)
   in the ixgbe driver.
   Use 'legacy' descriptors on the tx ring and prefetch slots gives
   about 20% speedup at 900 MHz. Another 7-10% would come from removing
   the explict calls to bus_dmamap* in the core (they are effectively
   NOPs in this case, but it takes expensive load of the per-buffer
   dma maps to figure out that they are all NULL.

   Rx performance not investigated.

I am postponing the MFC so i can import a few more improvements
before merging.

1 files changed, 15 insertions, 7 deletions

diff --git a/share/man/man4/netmap.4 b/share/man/man4/netmap.4
index 1ad574d..dfd96b0 100644
--- a/share/man/man4/netmap.4
+++ b/share/man/man4/netmap.4
@@ -28,7 +28,7 @@
 .\" $FreeBSD$
 .\" $Id: netmap.4 9662 2011-11-16 13:18:06Z luigi $: stable/8/share/man/man4/bpf.4 181694 2008-08-13 17:45:06Z ed $
 .\"
-.Dd November 16, 2011
+.Dd February 27, 2012
 .Dt NETMAP 4
 .Os
 .Sh NAME
@@ -123,8 +123,9 @@ one ring pair (numbered N) for packets from/to the host stack.
 struct netmap_ring {
     const ssize_t buf_ofs;
     const uint32_t num_slots; /* number of slots in the ring. */
-    uint32_t avail; /* number of usable slots */
-    uint32_t cur; /* 'current' index for the user side */
+    uint32_t avail;           /* number of usable slots */
+    uint32_t cur;             /* 'current' index for the user side */
+    uint32_t reserved;        /* not refilled before current */
 
     const uint16_t nr_buf_size;
     uint16_t flags;
@@ -173,10 +174,14 @@ defined as follows:
 .Bd -literal
 struct nmreq {
         char      nr_name[IFNAMSIZ];
+        uint32_t  nr_version;     /* API version */
+#define NETMAP_API      2         /* current version */
         uint32_t  nr_offset;      /* nifp offset in the shared region */
         uint32_t  nr_memsize;     /* size of the shared region */
-        uint32_t  nr_numdescs;    /* descriptors per queue */
-        uint16_t  nr_numqueues;
+        uint32_t  nr_tx_slots;    /* slots in tx rings */
+        uint32_t  nr_rx_slots;    /* slots in rx rings */
+        uint16_t  nr_tx_rings;    /* number of tx rings */
+        uint16_t  nr_rx_rings;    /* number of tx rings */
         uint16_t  nr_ringid;      /* ring(s) we care about */
 #define NETMAP_HW_RING  0x4000    /* low bits indicate one hw ring */
 #define NETMAP_SW_RING  0x2000    /* we process the sw ring */
@@ -199,8 +204,10 @@ and are:
 returns information about the interface named in nr_name.
 On return, nr_memsize indicates the size of the shared netmap
 memory region (this is device-independent),
-nr_numslots indicates how many buffers are in a ring,
-nr_numrings indicates the number of rings supported by the hardware.
+nr_tx_slots and nr_rx_slots indicates how many buffers are in a
+transmit and receive ring,
+nr_tx_rings and nr_rx_rings indicates the number of transmit
+and receive rings supported by the hardware.
 .Pp
 If the device does not support netmap, the ioctl returns EINVAL.
 .It Dv NIOCREGIF
@@ -266,6 +273,7 @@ struct netmap_request nmr;
 fd = open("/dev/netmap", O_RDWR);
 bzero(&nmr, sizeof(nmr));
 strcpy(nmr.nm_name, "ix0");
+nmr.nm_version = NETMAP_API;
 ioctl(fd, NIOCREG, &nmr);
 p = mmap(0, nmr.memsize, fd);
 nifp = NETMAP_IF(p, nmr.offset);