MFC r276480, r276485, r276498, r277225, r277226, r277227, r277230,

r277637, and r283149 (by emaste@).

r276485 is the real change here, the rest deal with the fallout of
mp_ring's reliance on 64b atomics.

Use the incorrectly spelled 'eigth' from struct pkthdr in this branch
instead of MFC'ing r261733, which would have renamed the field of a
public structure in a -STABLE branch.
---

r276480:
Temporarily unplug cxgbe(4) from !amd64 builds.

r276485:
cxgbe(4): major tx rework.

a) Front load as much work as possible in if_transmit, before any driver
lock or software queue has to get involved.

b) Replace buf_ring with a brand new mp_ring (multiproducer ring).  This
is specifically for the tx multiqueue model where one of the if_transmit
producer threads becomes the consumer and other producers carry on as
usual.  mp_ring is implemented as standalone code and it should be
possible to use it in any driver with tx multiqueue.  It also has:
- the ability to enqueue/dequeue multiple items.  This might become
  significant if packet batching is ever implemented.
- an abdication mechanism to allow a thread to give up writing tx
  descriptors and have another if_transmit thread take over.  A thread
  that's writing tx descriptors can end up doing so for an unbounded
  time period if a) there are other if_transmit threads continuously
  feeding the sofware queue, and b) the chip keeps up with whatever the
  thread is throwing at it.
- accurate statistics about interesting events even when the stats come
  at the expense of additional branches/conditional code.

The NIC txq lock is uncontested on the fast path at this point.  I've
left it there for synchronization with the control events (interface
up/down, modload/unload).

c) Add support for "type 1" coalescing work request in the normal NIC tx
path.  This work request is optimized for frames with a single item in
the DMA gather list.  These are very common when forwarding packets.
Note that netmap tx in cxgbe already uses these "type 1" work requests.

d) Do not request automatic cidx updates every 32 descriptors.  Instead,
request updates via bits in individual work requests (still every 32
descriptors approximately).  Also, request an automatic final update
when the queue idles after activity.  This means NIC tx reclaim is still
performed lazily but it will catch up quickly as soon as the queue
idles.  This seems to be the best middle ground and I'll probably do
something similar for netmap tx as well.

e) Implement a faster tx path for WRQs (used by TOE tx and control
queues, _not_ by the normal NIC tx).  Allow work requests to be written
directly to the hardware descriptor ring if room is available.  I will
convert t4_tom and iw_cxgbe modules to this faster style gradually.

r276498:
cxgbe(4): remove buf_ring specific restriction on the txq size.

r277225:
Make cxgbe(4) buildable with the gcc in base.

r277226:
Allow cxgbe(4) to be built on i386.  Driver attach will succeed only on
a subset of i386 systems.

r277227:
Plug cxgbe(4) back into !powerpc && !arm builds, instead of building it
on amd64 only.

r277230:
Build cxgbe(4) on powerpc64 too.

r277637:
Make sure the compiler flag to get cxgbe(4) to compile with gcc is used
only when gcc is being used.  This is what r277225 should have been.

1 files changed, 68 insertions, 0 deletions

diff --git a/sys/dev/cxgbe/t4_mp_ring.h b/sys/dev/cxgbe/t4_mp_ring.h
new file mode 100644
index 0000000..c9ee346
--- /dev/null
+++ b/sys/dev/cxgbe/t4_mp_ring.h
@@ -0,0 +1,68 @@
+/*-
+ * Copyright (c) 2014 Chelsio Communications, Inc.
+ * All rights reserved.
+ * Written by: Navdeep Parhar <np@FreeBSD.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ *
+ */
+
+#ifndef __CXGBE_MP_RING_H
+#define __CXGBE_MP_RING_H
+
+#ifndef _KERNEL
+#error "no user-serviceable parts inside"
+#endif
+
+struct mp_ring;
+typedef u_int (*ring_drain_t)(struct mp_ring *, u_int, u_int);
+typedef u_int (*ring_can_drain_t)(struct mp_ring *);
+
+struct mp_ring {
+	volatile uint64_t	state __aligned(CACHE_LINE_SIZE);
+
+	int			size __aligned(CACHE_LINE_SIZE);
+	void *			cookie;
+	struct malloc_type *	mt;
+	ring_drain_t		drain;
+	ring_can_drain_t	can_drain;	/* cheap, may be unreliable */
+	counter_u64_t		enqueues;
+	counter_u64_t		drops;
+	counter_u64_t		starts;
+	counter_u64_t		stalls;
+	counter_u64_t		restarts;	/* recovered after stalling */
+	counter_u64_t		abdications;
+
+	void * volatile		items[] __aligned(CACHE_LINE_SIZE);
+};
+
+int mp_ring_alloc(struct mp_ring **, int, void *, ring_drain_t,
+    ring_can_drain_t, struct malloc_type *, int);
+void mp_ring_free(struct mp_ring *);
+int mp_ring_enqueue(struct mp_ring *, void **, int, int);
+void mp_ring_check_drainage(struct mp_ring *, int);
+void mp_ring_reset_stats(struct mp_ring *);
+int mp_ring_is_idle(struct mp_ring *);
+
+#endif