FD.io VPP  v17.04.2-2-ga8f93f8
Vector Packet Processing
smp_fifo.h
Go to the documentation of this file.
1 /*
2  * Copyright (c) 2015 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  Copyright (c) 2012 Eliot Dresselhaus
17 
18  Permission is hereby granted, free of charge, to any person obtaining
19  a copy of this software and associated documentation files (the
20  "Software"), to deal in the Software without restriction, including
21  without limitation the rights to use, copy, modify, merge, publish,
22  distribute, sublicense, and/or sell copies of the Software, and to
23  permit persons to whom the Software is furnished to do so, subject to
24  the following conditions:
25 
26  The above copyright notice and this permission notice shall be
27  included in all copies or substantial portions of the Software.
28 
29  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
30  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
31  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
32  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
33  LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
34  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
35  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
36 */
37 
38 #ifndef included_clib_smp_vec_h
39 #define included_clib_smp_vec_h
40 
41 #include <vppinfra/smp.h>
42 
43 #define foreach_clib_smp_fifo_data_state \
44  _ (free) \
45  _ (write_alloc) \
46  _ (write_done) \
47  _ (read_fetch)
48 
49 typedef enum
50 {
51 #define _(f) CLIB_SMP_FIFO_DATA_STATE_##f,
53 #undef _
56 
57 /* Footer at end of each data element. */
58 typedef struct
59 {
60  /* Magic number marking valid footer plus state encoded in low bits. */
63 
64 #define CLIB_SMP_DATA_FOOTER_MAGIC 0xfafbfcf0
65 
68 {
70 
71  /* Check that magic number plus state is still valid. */
73  os_panic ();
74 
75  return s;
76 }
77 
78 always_inline void
81 {
83 }
84 
85 typedef struct
86 {
87  /* Read/write indices each on their own cache line.
88  Atomic incremented for each read/write. */
89  u32 read_index, write_index;
90 
91  /* Power of 2 number of elements in fifo less one. */
93 
94  /* Log2 of above. */
96 
97  /* Cache aligned data. */
98  void *data;
100 
101 /* External functions. */
102 clib_smp_fifo_t *clib_smp_fifo_init (uword max_n_elts, uword n_bytes_per_elt);
103 
104 /* Elements are always cache-line sized; this is to avoid smp cache thrashing. */
107 {
108  return round_pow2 (n_bytes_per_elt, CLIB_CACHE_LINE_BYTES);
109 }
110 
113 {
114  uword n = f->write_index - f->read_index;
115  ASSERT (n <= f->max_n_elts_less_one + 1);
116  return n;
117 }
118 
120 clib_smp_fifo_get_data_footer (void *d, uword n_bytes_per_elt)
121 {
123  f = d + clib_smp_fifo_round_elt_bytes (n_bytes_per_elt) - sizeof (f[0]);
124  return f;
125 }
126 
127 always_inline void *
129  uword i)
130 {
131  uword n_bytes_per_elt_cache_aligned;
132 
133  ASSERT (i <= f->max_n_elts_less_one);
134 
135  n_bytes_per_elt_cache_aligned =
136  clib_smp_fifo_round_elt_bytes (n_bytes_per_elt);
137 
138  return f->data + i * n_bytes_per_elt_cache_aligned;
139 }
140 
141 always_inline void *
143 {
144  void *d;
147  u32 wi0, wi1;
148 
149  wi0 = f->write_index;
150 
151  /* Fifo full? */
152  if (wi0 - f->read_index > f->max_n_elts_less_one)
153  return 0;
154 
155  while (1)
156  {
157  wi1 = wi0 + 1;
158 
159  d =
160  clib_smp_fifo_elt_at_index (f, n_bytes_per_elt,
161  wi0 & f->max_n_elts_less_one);
162  t = clib_smp_fifo_get_data_footer (d, n_bytes_per_elt);
163 
165  if (s != CLIB_SMP_FIFO_DATA_STATE_free)
166  {
167  d = 0;
168  break;
169  }
170 
171  wi1 = clib_smp_compare_and_swap (&f->write_index, wi1, wi0);
172 
173  if (wi1 == wi0)
174  {
176  CLIB_SMP_FIFO_DATA_STATE_write_alloc);
177  break;
178  }
179 
180  /* Other cpu wrote write index first: try again. */
181  wi0 = wi1;
182  }
183 
184  return d;
185 }
186 
187 always_inline void
188 clib_smp_fifo_write_done (clib_smp_fifo_t * f, void *d, uword n_bytes_per_elt)
189 {
191 
192  /* Flush out pending writes before we change state to write_done.
193  This will hold off readers until data is flushed. */
195 
196  t = clib_smp_fifo_get_data_footer (d, n_bytes_per_elt);
197 
199  CLIB_SMP_FIFO_DATA_STATE_write_alloc);
201  CLIB_SMP_FIFO_DATA_STATE_write_done);
202 }
203 
204 always_inline void *
206 {
207  void *d;
210  u32 ri0, ri1;
211 
212  ri0 = f->read_index;
213 
214  /* Fifo empty? */
215  if (f->write_index - ri0 == 0)
216  return 0;
217 
218  while (1)
219  {
220  ri1 = ri0 + 1;
221 
222  d =
223  clib_smp_fifo_elt_at_index (f, n_bytes_per_elt,
224  ri0 & f->max_n_elts_less_one);
225  t = clib_smp_fifo_get_data_footer (d, n_bytes_per_elt);
226 
228  if (s != CLIB_SMP_FIFO_DATA_STATE_write_done)
229  {
230  d = 0;
231  break;
232  }
233 
234  ri1 = clib_smp_compare_and_swap (&f->read_index, ri1, ri0);
235  if (ri1 == ri0)
236  {
238  CLIB_SMP_FIFO_DATA_STATE_read_fetch);
239  break;
240  }
241 
242  ri0 = ri1;
243  }
244 
245  return d;
246 }
247 
248 always_inline void
249 clib_smp_fifo_read_done (clib_smp_fifo_t * f, void *d, uword n_bytes_per_elt)
250 {
252 
253  t = clib_smp_fifo_get_data_footer (d, n_bytes_per_elt);
254 
256  CLIB_SMP_FIFO_DATA_STATE_read_fetch);
257  clib_smp_fifo_data_footer_set_state (t, CLIB_SMP_FIFO_DATA_STATE_free);
258 }
259 
260 always_inline void
261 clib_smp_fifo_memcpy (uword * dst, uword * src, uword n_bytes)
262 {
263  word n_bytes_left = n_bytes;
264 
265  while (n_bytes_left >= 4 * sizeof (uword))
266  {
267  dst[0] = src[0];
268  dst[1] = src[1];
269  dst[2] = src[2];
270  dst[3] = src[3];
271  dst += 4;
272  src += 4;
273  n_bytes_left -= 4 * sizeof (dst[0]);
274  }
275 
276  while (n_bytes_left > 0)
277  {
278  dst[0] = src[0];
279  dst += 1;
280  src += 1;
281  n_bytes_left -= 1 * sizeof (dst[0]);
282  }
283 }
284 
285 always_inline void
287  uword n_bytes_per_elt)
288 {
289  uword *dst;
290  dst = clib_smp_fifo_write_alloc (f, n_bytes_per_elt);
291  clib_smp_fifo_memcpy (dst, elt_to_write, n_bytes_per_elt);
292  clib_smp_fifo_write_done (f, dst, n_bytes_per_elt);
293 }
294 
295 always_inline void
297  uword n_bytes_per_elt)
298 {
299  uword *src;
300  src = clib_smp_fifo_read_fetch (f, n_bytes_per_elt);
301  clib_smp_fifo_memcpy (elt_to_read, src, n_bytes_per_elt);
302  clib_smp_fifo_read_done (f, src, n_bytes_per_elt);
303 }
304 
305 #endif /* included_clib_smp_vec_h */
306 
307 /*
308  * fd.io coding-style-patch-verification: ON
309  *
310  * Local Variables:
311  * eval: (c-set-style "gnu")
312  * End:
313  */
#define clib_smp_compare_and_swap(addr, new, old)
Definition: smp.h:44
sll srl srl sll sra u16x4 i
Definition: vector_sse2.h:343
static void clib_smp_fifo_memcpy(uword *dst, uword *src, uword n_bytes)
Definition: smp_fifo.h:261
static void clib_smp_fifo_write_inline(clib_smp_fifo_t *f, void *elt_to_write, uword n_bytes_per_elt)
Definition: smp_fifo.h:286
clib_smp_fifo_t * clib_smp_fifo_init(uword max_n_elts, uword n_bytes_per_elt)
Definition: smp_fifo.c:42
void os_panic(void)
Definition: unix-misc.c:172
static void * clib_smp_fifo_write_alloc(clib_smp_fifo_t *f, uword n_bytes_per_elt)
Definition: smp_fifo.h:142
#define always_inline
Definition: clib.h:84
#define foreach_clib_smp_fifo_data_state
Definition: smp_fifo.h:43
static void * clib_smp_fifo_read_fetch(clib_smp_fifo_t *f, uword n_bytes_per_elt)
Definition: smp_fifo.h:205
static uword clib_smp_fifo_round_elt_bytes(uword n_bytes_per_elt)
Definition: smp_fifo.h:106
clib_smp_fifo_data_state_t
Definition: smp_fifo.h:49
void * data
Definition: smp_fifo.h:98
static clib_smp_fifo_data_footer_t * clib_smp_fifo_get_data_footer(void *d, uword n_bytes_per_elt)
Definition: smp_fifo.h:120
static void clib_smp_fifo_read_done(clib_smp_fifo_t *f, void *d, uword n_bytes_per_elt)
Definition: smp_fifo.h:249
#define CLIB_SMP_DATA_FOOTER_MAGIC
Definition: smp_fifo.h:64
static uword round_pow2(uword x, uword pow2)
Definition: clib.h:278
#define ASSERT(truth)
unsigned int u32
Definition: types.h:88
u32 log2_max_n_elts
Definition: smp_fifo.h:95
static void clib_smp_fifo_data_footer_set_state(clib_smp_fifo_data_footer_t *f, clib_smp_fifo_data_state_t s)
Definition: smp_fifo.h:79
u64 uword
Definition: types.h:112
i64 word
Definition: types.h:111
static void clib_smp_fifo_read_inline(clib_smp_fifo_t *f, void *elt_to_read, uword n_bytes_per_elt)
Definition: smp_fifo.h:296
static clib_smp_fifo_data_state_t clib_smp_fifo_data_footer_get_state(clib_smp_fifo_data_footer_t *f)
Definition: smp_fifo.h:67
static void * clib_smp_fifo_elt_at_index(clib_smp_fifo_t *f, uword n_bytes_per_elt, uword i)
Definition: smp_fifo.h:128
#define CLIB_MEMORY_BARRIER()
Definition: clib.h:101
#define CLIB_CACHE_LINE_BYTES
Definition: cache.h:67
static uword clib_smp_fifo_n_elts(clib_smp_fifo_t *f)
Definition: smp_fifo.h:112
u32 max_n_elts_less_one
Definition: smp_fifo.h:92
static void clib_smp_fifo_write_done(clib_smp_fifo_t *f, void *d, uword n_bytes_per_elt)
Definition: smp_fifo.h:188