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Vector Packet Processing
refcount.h
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1 /*
2  * Copyright (c) 2016 Cisco and/or its affiliates.
3  * Licensed under the Apache License, Version 2.0 (the "License");
4  * you may not use this file except in compliance with the License.
5  * You may obtain a copy of the License at:
6  *
7  * http://www.apache.org/licenses/LICENSE-2.0
8  *
9  * Unless required by applicable law or agreed to in writing, software
10  * distributed under the License is distributed on an "AS IS" BASIS,
11  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12  * See the License for the specific language governing permissions and
13  * limitations under the License.
14  */
15 
16 /*
17  * vlib provides lock-free counters but those
18  * - Have 16bits per-CPU counter, which may overflow.
19  * - Would only increment.
20  *
21  * This is very similar to vlib counters, but may be used to count reference.
22  * Such a counter includes an arbitrary number of counters. Each counter
23  * is identified by its index. This is used to aggregate per-cpu memory.
24  *
25  * Warning:
26  * This reference counter is lock-free but is not race-condition free.
27  * The counting result is approximate and another mechanism needs to be used
28  * in order to ensure that an object may be freed.
29  *
30  */
31 
32 #include <vnet/vnet.h>
33 
34 /*
35  * Reference counting
36  * A specific reference counter is used. The design is quite
37  * similar to vlib counters but:
38  * - It is possible to decrease the value
39  * - Summing will not zero the per-thread counters
40  * - Only the thread can reallocate its own counters vector (to avoid concurrency issues)
41 */
42 typedef struct {
44  volatile u32 *counter_lock;
47 
48 typedef struct {
51 
53 void vlib_refcount_lock (volatile u32 *counter_lock)
54 {
55  while (clib_atomic_test_and_set (counter_lock))
56  ;
57 }
58 
60 void vlib_refcount_unlock (volatile u32 *counter_lock)
61 {
62  clib_atomic_release(counter_lock);
63 }
64 
65 void __vlib_refcount_resize(vlib_refcount_per_cpu_t *per_cpu, u32 size);
66 
69 {
70  vlib_refcount_per_cpu_t *per_cpu = &r->per_cpu[thread_index];
71  if (PREDICT_FALSE(counter_index >= vec_len(per_cpu->counters)))
72  __vlib_refcount_resize(per_cpu, clib_max(counter_index + 16,(vec_len(per_cpu->counters)) * 2));
73 
74  per_cpu->counters[counter_index] += v;
75 }
76 
78 
81 {
83  u32 thread_index;
84  r->per_cpu = 0;
85  vec_validate (r->per_cpu, tm->n_vlib_mains - 1);
86 
87  for (thread_index = 0; thread_index < tm->n_vlib_mains; thread_index++)
88  {
89  r->per_cpu[thread_index].counter_lock =
91  r->per_cpu[thread_index].counter_lock[0] = 0;
92  }
93 }
94 
95 
#define vec_validate(V, I)
Make sure vector is long enough for given index (no header, unspecified alignment) ...
Definition: vec.h:439
#define CLIB_CACHE_LINE_ALIGN_MARK(mark)
Definition: cache.h:60
volatile u32 * counter_lock
Definition: refcount.h:44
unsigned long u64
Definition: types.h:89
u64 vlib_refcount_get(vlib_refcount_t *r, u32 index)
Definition: refcount.c:31
static_always_inline void vlib_refcount_init(vlib_refcount_t *r)
Definition: refcount.h:80
#define static_always_inline
Definition: clib.h:99
unsigned int u32
Definition: types.h:88
#define clib_atomic_test_and_set(a)
Definition: atomics.h:40
uword size
#define clib_atomic_release(a)
Definition: atomics.h:41
#define PREDICT_FALSE(x)
Definition: clib.h:111
static_always_inline void vlib_refcount_unlock(volatile u32 *counter_lock)
Definition: refcount.h:60
static u32 counter_index(vlib_main_t *vm, vlib_error_t e)
Definition: drop.c:67
static_always_inline void vlib_refcount_add(vlib_refcount_t *r, u32 thread_index, u32 counter_index, i32 v)
Definition: refcount.h:68
signed int i32
Definition: types.h:77
#define clib_max(x, y)
Definition: clib.h:288
static_always_inline void vlib_refcount_lock(volatile u32 *counter_lock)
Definition: refcount.h:53
#define vec_len(v)
Number of elements in vector (rvalue-only, NULL tolerant)
static void * clib_mem_alloc_aligned(uword size, uword align)
Definition: mem.h:140
static vlib_thread_main_t * vlib_get_thread_main()
Definition: global_funcs.h:32
#define CLIB_CACHE_LINE_BYTES
Definition: cache.h:59
vlib_refcount_per_cpu_t * per_cpu
Definition: refcount.h:49