VPP-130: MagLev-like Load Balancer

This plugin provides load balancing for VPP in a way that is largely inspired
from Google's MagLev: http://research.google.com/pubs/pub44824.html

More info in the README.md

Change-Id: I1223f495d5c2d5200808a398504119f2830337e9
Signed-off-by: Pierre Pfister <ppfister@cisco.com>

1 files changed, 67 insertions, 0 deletions

diff --git a/plugins/lb-plugin/lb/refcount.h b/plugins/lb-plugin/lb/refcount.h
new file mode 100644
index 00000000000..8c26e7be76f
--- /dev/null
+++ b/plugins/lb-plugin/lb/refcount.h
@@ -0,0 +1,67 @@
+/*
+ * Copyright (c) 2016 Cisco and/or its affiliates.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/*
+ * vlib provides lock-free counters but those
+ * - Have 16bits per-CPU counter, which may overflow.
+ * - Would only increment.
+ *
+ * This is very similar to vlib counters, but may be used to count reference.
+ * Such a counter includes an arbitrary number of counters. Each counter
+ * is identified by its index. This is used to aggregate per-cpu memory.
+ *
+ * Warning:
+ *   This reference counter is lock-free but is not race-condition free.
+ *   The counting result is approximate and another mechanism needs to be used
+ *   in order to ensure that an object may be freed.
+ *
+ */
+
+#include <vnet/vnet.h>
+
+typedef struct {
+  u32 *counters;
+  u32 length;
+  u32 *reader_lengths;
+  CLIB_CACHE_LINE_ALIGN_MARK(o);
+} vlib_refcount_per_cpu_t;
+
+typedef struct {
+  vlib_refcount_per_cpu_t *per_cpu;
+} vlib_refcount_t;
+
+void __vlib_refcount_resize(vlib_refcount_per_cpu_t *per_cpu, u32 size);
+
+static_always_inline
+void vlib_refcount_add(vlib_refcount_t *r, u32 cpu_index, u32 counter_index, i32 v)
+{
+  vlib_refcount_per_cpu_t *per_cpu = &r->per_cpu[cpu_index];
+  if (PREDICT_FALSE(counter_index >= per_cpu->length))
+    __vlib_refcount_resize(per_cpu, clib_max(counter_index + 16, per_cpu->length * 2));
+
+  per_cpu->counters[counter_index] += v;
+}
+
+u64 vlib_refcount_get(vlib_refcount_t *r, u32 index);
+
+static_always_inline
+void vlib_refcount_init(vlib_refcount_t *r)
+{
+  vlib_thread_main_t *tm = vlib_get_thread_main ();
+  r->per_cpu = 0;
+  vec_validate (r->per_cpu, tm->n_vlib_mains - 1);
+}
+
+