1 /* SPDX-License-Identifier: BSD-3-Clause
2  * Copyright(c) 2010-2014 Intel Corporation
3  */
4 
5 #include <stdio.h>
6 #include <sys/queue.h>
7 #include <string.h>
8 #include <rte_mbuf.h>
9 #include <rte_memory.h>
10 #include <rte_memzone.h>
11 #include <rte_errno.h>
12 #include <rte_string_fns.h>
13 #include <rte_eal_memconfig.h>
14 #include <rte_pause.h>
15 #include <rte_tailq.h>
16 
17 #include "rte_distributor_single.h"
18 #include "distributor_private.h"
19 
20 TAILQ_HEAD(rte_distributor_list, rte_distributor_single);
21 
22 static struct rte_tailq_elem rte_distributor_tailq = {
23 	.name = "RTE_DISTRIBUTOR",
24 };
25 EAL_REGISTER_TAILQ(rte_distributor_tailq)
26 
27 /**** APIs called by workers ****/
28 
29 void
30 rte_distributor_request_pkt_single(struct rte_distributor_single *d,
31 		unsigned worker_id, struct rte_mbuf *oldpkt)
32 {
33 	union rte_distributor_buffer_single *buf = &d->bufs[worker_id];
34 	int64_t req = (((int64_t)(uintptr_t)oldpkt) << RTE_DISTRIB_FLAG_BITS)
35 			| RTE_DISTRIB_GET_BUF;
36 	while (unlikely(__atomic_load_n(&buf->bufptr64, __ATOMIC_RELAXED)
37 			& RTE_DISTRIB_FLAGS_MASK))
38 		rte_pause();
39 
40 	/* Sync with distributor on GET_BUF flag. */
41 	__atomic_store_n(&(buf->bufptr64), req, __ATOMIC_RELEASE);
42 }
43 
44 struct rte_mbuf *
45 rte_distributor_poll_pkt_single(struct rte_distributor_single *d,
46 		unsigned worker_id)
47 {
48 	union rte_distributor_buffer_single *buf = &d->bufs[worker_id];
49 	/* Sync with distributor. Acquire bufptr64. */
50 	if (__atomic_load_n(&buf->bufptr64, __ATOMIC_ACQUIRE)
51 		& RTE_DISTRIB_GET_BUF)
52 		return NULL;
53 
54 	/* since bufptr64 is signed, this should be an arithmetic shift */
55 	int64_t ret = buf->bufptr64 >> RTE_DISTRIB_FLAG_BITS;
56 	return (struct rte_mbuf *)((uintptr_t)ret);
57 }
58 
59 struct rte_mbuf *
60 rte_distributor_get_pkt_single(struct rte_distributor_single *d,
61 		unsigned worker_id, struct rte_mbuf *oldpkt)
62 {
63 	struct rte_mbuf *ret;
64 	rte_distributor_request_pkt_single(d, worker_id, oldpkt);
65 	while ((ret = rte_distributor_poll_pkt_single(d, worker_id)) == NULL)
66 		rte_pause();
67 	return ret;
68 }
69 
70 int
71 rte_distributor_return_pkt_single(struct rte_distributor_single *d,
72 		unsigned worker_id, struct rte_mbuf *oldpkt)
73 {
74 	union rte_distributor_buffer_single *buf = &d->bufs[worker_id];
75 	uint64_t req = (((int64_t)(uintptr_t)oldpkt) << RTE_DISTRIB_FLAG_BITS)
76 			| RTE_DISTRIB_RETURN_BUF;
77 	while (unlikely(__atomic_load_n(&buf->bufptr64, __ATOMIC_RELAXED)
78 			& RTE_DISTRIB_FLAGS_MASK))
79 		rte_pause();
80 
81 	/* Sync with distributor on RETURN_BUF flag. */
82 	__atomic_store_n(&(buf->bufptr64), req, __ATOMIC_RELEASE);
83 	return 0;
84 }
85 
86 /**** APIs called on distributor core ***/
87 
88 /* as name suggests, adds a packet to the backlog for a particular worker */
89 static int
90 add_to_backlog(struct rte_distributor_backlog *bl, int64_t item)
91 {
92 	if (bl->count == RTE_DISTRIB_BACKLOG_SIZE)
93 		return -1;
94 
95 	bl->pkts[(bl->start + bl->count++) & (RTE_DISTRIB_BACKLOG_MASK)]
96 			= item;
97 	return 0;
98 }
99 
100 /* takes the next packet for a worker off the backlog */
101 static int64_t
102 backlog_pop(struct rte_distributor_backlog *bl)
103 {
104 	bl->count--;
105 	return bl->pkts[bl->start++ & RTE_DISTRIB_BACKLOG_MASK];
106 }
107 
108 /* stores a packet returned from a worker inside the returns array */
109 static inline void
110 store_return(uintptr_t oldbuf, struct rte_distributor_single *d,
111 		unsigned *ret_start, unsigned *ret_count)
112 {
113 	/* store returns in a circular buffer - code is branch-free */
114 	d->returns.mbufs[(*ret_start + *ret_count) & RTE_DISTRIB_RETURNS_MASK]
115 			= (void *)oldbuf;
116 	*ret_start += (*ret_count == RTE_DISTRIB_RETURNS_MASK) & !!(oldbuf);
117 	*ret_count += (*ret_count != RTE_DISTRIB_RETURNS_MASK) & !!(oldbuf);
118 }
119 
120 static inline void
121 handle_worker_shutdown(struct rte_distributor_single *d, unsigned int wkr)
122 {
123 	d->in_flight_tags[wkr] = 0;
124 	d->in_flight_bitmask &= ~(1UL << wkr);
125 	/* Sync with worker. Release bufptr64. */
126 	__atomic_store_n(&(d->bufs[wkr].bufptr64), 0, __ATOMIC_RELEASE);
127 	if (unlikely(d->backlog[wkr].count != 0)) {
128 		/* On return of a packet, we need to move the
129 		 * queued packets for this core elsewhere.
130 		 * Easiest solution is to set things up for
131 		 * a recursive call. That will cause those
132 		 * packets to be queued up for the next free
133 		 * core, i.e. it will return as soon as a
134 		 * core becomes free to accept the first
135 		 * packet, as subsequent ones will be added to
136 		 * the backlog for that core.
137 		 */
138 		struct rte_mbuf *pkts[RTE_DISTRIB_BACKLOG_SIZE];
139 		unsigned i;
140 		struct rte_distributor_backlog *bl = &d->backlog[wkr];
141 
142 		for (i = 0; i < bl->count; i++) {
143 			unsigned idx = (bl->start + i) &
144 					RTE_DISTRIB_BACKLOG_MASK;
145 			pkts[i] = (void *)((uintptr_t)(bl->pkts[idx] >>
146 					RTE_DISTRIB_FLAG_BITS));
147 		}
148 		/* recursive call.
149 		 * Note that the tags were set before first level call
150 		 * to rte_distributor_process.
151 		 */
152 		rte_distributor_process_single(d, pkts, i);
153 		bl->count = bl->start = 0;
154 	}
155 }
156 
157 /* this function is called when process() fn is called without any new
158  * packets. It goes through all the workers and clears any returned packets
159  * to do a partial flush.
160  */
161 static int
162 process_returns(struct rte_distributor_single *d)
163 {
164 	unsigned wkr;
165 	unsigned flushed = 0;
166 	unsigned ret_start = d->returns.start,
167 			ret_count = d->returns.count;
168 
169 	for (wkr = 0; wkr < d->num_workers; wkr++) {
170 		uintptr_t oldbuf = 0;
171 		/* Sync with worker. Acquire bufptr64. */
172 		const int64_t data = __atomic_load_n(&(d->bufs[wkr].bufptr64),
173 							__ATOMIC_ACQUIRE);
174 
175 		if (data & RTE_DISTRIB_GET_BUF) {
176 			flushed++;
177 			if (d->backlog[wkr].count)
178 				/* Sync with worker. Release bufptr64. */
179 				__atomic_store_n(&(d->bufs[wkr].bufptr64),
180 					backlog_pop(&d->backlog[wkr]),
181 					__ATOMIC_RELEASE);
182 			else {
183 				/* Sync with worker on GET_BUF flag. */
184 				__atomic_store_n(&(d->bufs[wkr].bufptr64),
185 					RTE_DISTRIB_GET_BUF,
186 					__ATOMIC_RELEASE);
187 				d->in_flight_tags[wkr] = 0;
188 				d->in_flight_bitmask &= ~(1UL << wkr);
189 			}
190 			oldbuf = data >> RTE_DISTRIB_FLAG_BITS;
191 		} else if (data & RTE_DISTRIB_RETURN_BUF) {
192 			handle_worker_shutdown(d, wkr);
193 			oldbuf = data >> RTE_DISTRIB_FLAG_BITS;
194 		}
195 
196 		store_return(oldbuf, d, &ret_start, &ret_count);
197 	}
198 
199 	d->returns.start = ret_start;
200 	d->returns.count = ret_count;
201 
202 	return flushed;
203 }
204 
205 /* process a set of packets to distribute them to workers */
206 int
207 rte_distributor_process_single(struct rte_distributor_single *d,
208 		struct rte_mbuf **mbufs, unsigned num_mbufs)
209 {
210 	unsigned next_idx = 0;
211 	unsigned wkr = 0;
212 	struct rte_mbuf *next_mb = NULL;
213 	int64_t next_value = 0;
214 	uint32_t new_tag = 0;
215 	unsigned ret_start = d->returns.start,
216 			ret_count = d->returns.count;
217 
218 	if (unlikely(num_mbufs == 0))
219 		return process_returns(d);
220 
221 	while (next_idx < num_mbufs || next_mb != NULL) {
222 		uintptr_t oldbuf = 0;
223 		/* Sync with worker. Acquire bufptr64. */
224 		int64_t data = __atomic_load_n(&(d->bufs[wkr].bufptr64),
225 						__ATOMIC_ACQUIRE);
226 
227 		if (!next_mb) {
228 			next_mb = mbufs[next_idx++];
229 			next_value = (((int64_t)(uintptr_t)next_mb)
230 					<< RTE_DISTRIB_FLAG_BITS);
231 			/*
232 			 * User is advocated to set tag value for each
233 			 * mbuf before calling rte_distributor_process.
234 			 * User defined tags are used to identify flows,
235 			 * or sessions.
236 			 */
237 			new_tag = next_mb->hash.usr;
238 
239 			/*
240 			 * Note that if RTE_DISTRIB_MAX_WORKERS is larger than 64
241 			 * then the size of match has to be expanded.
242 			 */
243 			uint64_t match = 0;
244 			unsigned i;
245 			/*
246 			 * to scan for a match use "xor" and "not" to get a 0/1
247 			 * value, then use shifting to merge to single "match"
248 			 * variable, where a one-bit indicates a match for the
249 			 * worker given by the bit-position
250 			 */
251 			for (i = 0; i < d->num_workers; i++)
252 				match |= (!(d->in_flight_tags[i] ^ new_tag)
253 					<< i);
254 
255 			/* Only turned-on bits are considered as match */
256 			match &= d->in_flight_bitmask;
257 
258 			if (match) {
259 				next_mb = NULL;
260 				unsigned worker = __builtin_ctzl(match);
261 				if (add_to_backlog(&d->backlog[worker],
262 						next_value) < 0)
263 					next_idx--;
264 			}
265 		}
266 
267 		if ((data & RTE_DISTRIB_GET_BUF) &&
268 				(d->backlog[wkr].count || next_mb)) {
269 
270 			if (d->backlog[wkr].count)
271 				/* Sync with worker. Release bufptr64. */
272 				__atomic_store_n(&(d->bufs[wkr].bufptr64),
273 						backlog_pop(&d->backlog[wkr]),
274 						__ATOMIC_RELEASE);
275 
276 			else {
277 				/* Sync with worker. Release bufptr64.  */
278 				__atomic_store_n(&(d->bufs[wkr].bufptr64),
279 						next_value,
280 						__ATOMIC_RELEASE);
281 				d->in_flight_tags[wkr] = new_tag;
282 				d->in_flight_bitmask |= (1UL << wkr);
283 				next_mb = NULL;
284 			}
285 			oldbuf = data >> RTE_DISTRIB_FLAG_BITS;
286 		} else if (data & RTE_DISTRIB_RETURN_BUF) {
287 			handle_worker_shutdown(d, wkr);
288 			oldbuf = data >> RTE_DISTRIB_FLAG_BITS;
289 		}
290 
291 		/* store returns in a circular buffer */
292 		store_return(oldbuf, d, &ret_start, &ret_count);
293 
294 		if (++wkr == d->num_workers)
295 			wkr = 0;
296 	}
297 	/* to finish, check all workers for backlog and schedule work for them
298 	 * if they are ready */
299 	for (wkr = 0; wkr < d->num_workers; wkr++)
300 		if (d->backlog[wkr].count &&
301 				/* Sync with worker. Acquire bufptr64. */
302 				(__atomic_load_n(&(d->bufs[wkr].bufptr64),
303 				__ATOMIC_ACQUIRE) & RTE_DISTRIB_GET_BUF)) {
304 
305 			int64_t oldbuf = d->bufs[wkr].bufptr64 >>
306 					RTE_DISTRIB_FLAG_BITS;
307 
308 			store_return(oldbuf, d, &ret_start, &ret_count);
309 
310 			/* Sync with worker. Release bufptr64. */
311 			__atomic_store_n(&(d->bufs[wkr].bufptr64),
312 				backlog_pop(&d->backlog[wkr]),
313 				__ATOMIC_RELEASE);
314 		}
315 
316 	d->returns.start = ret_start;
317 	d->returns.count = ret_count;
318 	return num_mbufs;
319 }
320 
321 /* return to the caller, packets returned from workers */
322 int
323 rte_distributor_returned_pkts_single(struct rte_distributor_single *d,
324 		struct rte_mbuf **mbufs, unsigned max_mbufs)
325 {
326 	struct rte_distributor_returned_pkts *returns = &d->returns;
327 	unsigned retval = (max_mbufs < returns->count) ?
328 			max_mbufs : returns->count;
329 	unsigned i;
330 
331 	for (i = 0; i < retval; i++) {
332 		unsigned idx = (returns->start + i) & RTE_DISTRIB_RETURNS_MASK;
333 		mbufs[i] = returns->mbufs[idx];
334 	}
335 	returns->start += i;
336 	returns->count -= i;
337 
338 	return retval;
339 }
340 
341 /* return the number of packets in-flight in a distributor, i.e. packets
342  * being worked on or queued up in a backlog.
343  */
344 static inline unsigned
345 total_outstanding(const struct rte_distributor_single *d)
346 {
347 	unsigned wkr, total_outstanding;
348 
349 	total_outstanding = __builtin_popcountl(d->in_flight_bitmask);
350 
351 	for (wkr = 0; wkr < d->num_workers; wkr++)
352 		total_outstanding += d->backlog[wkr].count;
353 
354 	return total_outstanding;
355 }
356 
357 /* flush the distributor, so that there are no outstanding packets in flight or
358  * queued up. */
359 int
360 rte_distributor_flush_single(struct rte_distributor_single *d)
361 {
362 	const unsigned flushed = total_outstanding(d);
363 
364 	while (total_outstanding(d) > 0)
365 		rte_distributor_process_single(d, NULL, 0);
366 
367 	return flushed;
368 }
369 
370 /* clears the internal returns array in the distributor */
371 void
372 rte_distributor_clear_returns_single(struct rte_distributor_single *d)
373 {
374 	d->returns.start = d->returns.count = 0;
375 #ifndef __OPTIMIZE__
376 	memset(d->returns.mbufs, 0, sizeof(d->returns.mbufs));
377 #endif
378 }
379 
380 /* creates a distributor instance */
381 struct rte_distributor_single *
382 rte_distributor_create_single(const char *name,
383 		unsigned socket_id,
384 		unsigned num_workers)
385 {
386 	struct rte_distributor_single *d;
387 	struct rte_distributor_list *distributor_list;
388 	char mz_name[RTE_MEMZONE_NAMESIZE];
389 	const struct rte_memzone *mz;
390 
391 	/* compilation-time checks */
392 	RTE_BUILD_BUG_ON((sizeof(*d) & RTE_CACHE_LINE_MASK) != 0);
393 	RTE_BUILD_BUG_ON((RTE_DISTRIB_MAX_WORKERS & 7) != 0);
394 	RTE_BUILD_BUG_ON(RTE_DISTRIB_MAX_WORKERS >
395 				sizeof(d->in_flight_bitmask) * CHAR_BIT);
396 
397 	if (name == NULL || num_workers >= RTE_DISTRIB_MAX_WORKERS) {
398 		rte_errno = EINVAL;
399 		return NULL;
400 	}
401 
402 	snprintf(mz_name, sizeof(mz_name), RTE_DISTRIB_PREFIX"%s", name);
403 	mz = rte_memzone_reserve(mz_name, sizeof(*d), socket_id, NO_FLAGS);
404 	if (mz == NULL) {
405 		rte_errno = ENOMEM;
406 		return NULL;
407 	}
408 
409 	d = mz->addr;
410 	strlcpy(d->name, name, sizeof(d->name));
411 	d->num_workers = num_workers;
412 
413 	distributor_list = RTE_TAILQ_CAST(rte_distributor_tailq.head,
414 					  rte_distributor_list);
415 
416 	rte_mcfg_tailq_write_lock();
417 	TAILQ_INSERT_TAIL(distributor_list, d, next);
418 	rte_mcfg_tailq_write_unlock();
419 
420 	return d;
421 }
422