lsquic_spi.c revision 03fb9352 
1/* Copyright (c) 2017 - 2019 LiteSpeed Technologies Inc.  See LICENSE. */
2/*
3 * lsquic_spi.c - implementation of Stream Priority Iterator.
4 */
5
6#include <assert.h>
7#include <inttypes.h>
8#include <stdint.h>
9#include <stdlib.h>
10#include <string.h>
11#include <sys/queue.h>
12#include <sys/types.h>
13#ifdef WIN32
14#include <vc_compat.h>
15#endif
16
17#include "lsquic_types.h"
18#include "lsquic_int_types.h"
19#include "lsquic_sfcw.h"
20#include "lsquic_stream.h"
21#include "lsquic_spi.h"
22
23#define LSQUIC_LOGGER_MODULE LSQLM_SPI
24#define LSQUIC_LOG_CONN_ID iter->spi_cid
25#include "lsquic_logger.h"
26
27#define SPI_DEBUG(fmt, ...) LSQ_DEBUG("%s: " fmt, iter->spi_name, __VA_ARGS__)
28
29#define NEXT_STREAM(stream, off) \
30    (* (struct lsquic_stream **) ((unsigned char *) (stream) + (off)))
31
32
33static void
34add_stream_to_spi (struct stream_prio_iter *iter, lsquic_stream_t *stream)
35{
36    unsigned set, bit;
37    set = stream->sm_priority >> 6;
38    bit = stream->sm_priority & 0x3F;
39    if (!(iter->spi_set[set] & (1ULL << bit)))
40    {
41        iter->spi_set[set] |= 1ULL << bit;
42        TAILQ_INIT(&iter->spi_streams[ stream->sm_priority ]);
43    }
44    TAILQ_INSERT_TAIL(&iter->spi_streams[ stream->sm_priority ],
45                                                stream, next_prio_stream);
46}
47
48
49void
50lsquic_spi_init (struct stream_prio_iter *iter, struct lsquic_stream *first,
51        struct lsquic_stream *last, uintptr_t next_ptr_offset,
52        enum stream_flags onlist_mask, lsquic_cid_t cid, const char *name,
53        int (*filter)(void *filter_ctx, struct lsquic_stream *),
54        void *filter_ctx)
55{
56    struct lsquic_stream *stream;
57    unsigned count;
58
59    iter->spi_cid           = cid;
60    iter->spi_name          = name ? name : "UNSET";
61    iter->spi_set[0]        = 0;
62    iter->spi_set[1]        = 0;
63    iter->spi_set[2]        = 0;
64    iter->spi_set[3]        = 0;
65    iter->spi_onlist_mask   = onlist_mask;
66    iter->spi_cur_prio      = 0;
67    iter->spi_prev_stream   = NULL;
68    iter->spi_next_stream   = NULL;
69
70    stream = first;
71    count = 0;
72
73    if (filter)
74        while (1)
75        {
76            if (filter(filter_ctx, stream))
77            {
78                add_stream_to_spi(iter, stream);
79                ++count;
80            }
81            if (stream == last)
82                break;
83            stream = NEXT_STREAM(stream, next_ptr_offset);
84        }
85    else
86        while (1)
87        {
88            add_stream_to_spi(iter, stream);
89            ++count;
90            if (stream == last)
91                break;
92            stream = NEXT_STREAM(stream, next_ptr_offset);
93        }
94
95    if (count > 2)
96        SPI_DEBUG("initialized; # elems: %u; sets: [ %016"PRIX64", %016"PRIX64
97            ", %016"PRIX64", %016"PRIX64" ]", count, iter->spi_set[0],
98            iter->spi_set[1], iter->spi_set[2], iter->spi_set[3]);
99}
100
101
102static int
103find_and_set_lowest_priority (struct stream_prio_iter *iter)
104{
105    unsigned set, prio;
106    uint64_t mask;
107
108    for (set = 0, prio = 0; set < 4; ++set, prio += 64)
109        if (iter->spi_set[ set ])
110            break;
111
112    if (set == 4)
113    {
114        //SPI_DEBUG("%s: cannot find any", __func__);
115        return -1;
116    }
117
118    mask = iter->spi_set[set];
119    if (!(mask & ((1ULL << 32) - 1))) { prio += 32; mask >>= 32; }
120    if (!(mask & ((1ULL << 16) - 1))) { prio += 16; mask >>= 16; }
121    if (!(mask & ((1ULL <<  8) - 1))) { prio +=  8; mask >>=  8; }
122    if (!(mask & ((1ULL <<  4) - 1))) { prio +=  4; mask >>=  4; }
123    if (!(mask & ((1ULL <<  2) - 1))) { prio +=  2; mask >>=  2; }
124    if (!(mask & ((1ULL <<  1) - 1))) { prio +=  1;              }
125
126#ifndef NDEBUG
127    unsigned bit;
128    set = prio >> 6;
129    bit = prio & 0x3F;
130    assert(iter->spi_set[ set ] & (1ULL << bit));
131#endif
132
133    SPI_DEBUG("%s: prio %u -> %u", __func__, iter->spi_cur_prio, prio);
134    iter->spi_cur_prio = (unsigned char) prio;
135    return 0;
136}
137
138
139static int
140find_and_set_next_priority (struct stream_prio_iter *iter)
141{
142    unsigned set, bit, prio;
143    uint64_t mask;
144
145    /* Examine values in the same set first */
146    set = iter->spi_cur_prio >> 6;
147    bit = iter->spi_cur_prio & 0x3F;
148    prio = 64 * set;
149
150    if (bit < 63)
151    {
152        mask = iter->spi_set[set];
153        mask &= ~((1ULL << (bit + 1)) - 1);
154        if (mask)
155            goto calc_priority;
156    }
157
158    ++set;
159    prio += 64;
160    for (; set < 4; ++set, prio += 64)
161        if (iter->spi_set[ set ])
162            break;
163
164    if (set >= 4)
165    {
166        //SPI_DEBUG("%s: cannot find any", __func__);
167        return -1;
168    }
169
170    mask = iter->spi_set[set];
171
172  calc_priority:
173    if (!(mask & ((1ULL << 32) - 1))) { prio += 32; mask >>= 32; }
174    if (!(mask & ((1ULL << 16) - 1))) { prio += 16; mask >>= 16; }
175    if (!(mask & ((1ULL <<  8) - 1))) { prio +=  8; mask >>=  8; }
176    if (!(mask & ((1ULL <<  4) - 1))) { prio +=  4; mask >>=  4; }
177    if (!(mask & ((1ULL <<  2) - 1))) { prio +=  2; mask >>=  2; }
178    if (!(mask & ((1ULL <<  1) - 1))) { prio +=  1;              }
179
180#ifndef NDEBUG
181    set = prio >> 6;
182    bit = prio & 0x3F;
183    assert(iter->spi_set[ set ] & (1ULL << bit));
184#endif
185
186    SPI_DEBUG("%s: prio %u -> %u", __func__, iter->spi_cur_prio, prio);
187    iter->spi_cur_prio = (unsigned char) prio;
188    return 0;
189}
190
191
192/* Each stream returned by the iterator is processed in some fashion.  If,
193 * as a result of this, the stream gets taken off the original list, we
194 * have to follow suit and remove it from the iterator's set of streams.
195 */
196static void
197maybe_evict_prev (struct stream_prio_iter *iter)
198{
199    unsigned set, bit;
200
201    if (0 == (iter->spi_prev_stream->stream_flags & iter->spi_onlist_mask))
202    {
203        SPI_DEBUG("evict stream %u", iter->spi_prev_stream->id);
204        TAILQ_REMOVE(&iter->spi_streams[ iter->spi_prev_prio ],
205                                    iter->spi_prev_stream, next_prio_stream);
206        if (TAILQ_EMPTY(&iter->spi_streams[ iter->spi_prev_prio ]))
207        {
208            set = iter->spi_prev_prio >> 6;
209            bit = iter->spi_prev_prio & 0x3F;
210            iter->spi_set[ set ] &= ~(1ULL << bit);
211            SPI_DEBUG("priority %u now has no elements", iter->spi_prev_prio);
212        }
213        iter->spi_prev_stream = NULL;
214    }
215}
216
217
218lsquic_stream_t *
219lsquic_spi_first (struct stream_prio_iter *iter)
220{
221    lsquic_stream_t *stream;
222    unsigned set, bit;
223
224    if (iter->spi_prev_stream)
225        maybe_evict_prev(iter);
226
227    iter->spi_cur_prio = 0;
228    set = iter->spi_cur_prio >> 6;
229    bit = iter->spi_cur_prio & 0x3F;
230
231    if (!(iter->spi_set[set] & (1ULL << bit)))
232    {
233        if (0 != find_and_set_lowest_priority(iter))
234        {
235            SPI_DEBUG("%s: return NULL", __func__);
236            return NULL;
237        }
238    }
239
240    stream = TAILQ_FIRST(&iter->spi_streams[ iter->spi_cur_prio ]);
241    iter->spi_prev_prio   = iter->spi_cur_prio;
242    iter->spi_prev_stream = stream;
243    iter->spi_next_stream = TAILQ_NEXT(stream, next_prio_stream);
244    if (stream->id != 1 && stream->id != 3)
245        SPI_DEBUG("%s: return stream %u, priority %u", __func__, stream->id,
246                                                            iter->spi_cur_prio);
247    return stream;
248}
249
250
251lsquic_stream_t *
252lsquic_spi_next (struct stream_prio_iter *iter)
253{
254    lsquic_stream_t *stream;
255
256    if (iter->spi_prev_stream)
257        maybe_evict_prev(iter);
258
259    stream = iter->spi_next_stream;
260    if (stream)
261    {
262        assert(iter->spi_prev_prio == iter->spi_cur_prio);
263        iter->spi_prev_stream = stream;
264        iter->spi_next_stream = TAILQ_NEXT(stream, next_prio_stream);
265        if (stream->id != 1 && stream->id != 3)
266            SPI_DEBUG("%s: return stream %u, priority %u", __func__, stream->id,
267                                                            iter->spi_cur_prio);
268        return stream;
269    }
270
271    if (0 != find_and_set_next_priority(iter))
272    {
273        //SPI_DEBUG("%s: return NULL", __func__);
274        return NULL;
275    }
276
277    stream = TAILQ_FIRST(&iter->spi_streams[ iter->spi_cur_prio ]);
278    iter->spi_prev_prio   = iter->spi_cur_prio;
279    iter->spi_prev_stream = stream;
280    iter->spi_next_stream = TAILQ_NEXT(stream, next_prio_stream);
281
282    if (!lsquic_stream_is_critical(stream))
283        SPI_DEBUG("%s: return stream %u, priority %u", __func__, stream->id,
284                                                        iter->spi_cur_prio);
285    return stream;
286}
287
288
289static int
290have_non_critical_streams (const struct stream_prio_iter *iter)
291{
292    const struct lsquic_stream *stream;
293    TAILQ_FOREACH(stream, &iter->spi_streams[ iter->spi_cur_prio ],
294                                                        next_prio_stream)
295        if (!lsquic_stream_is_critical(stream))
296            return 1;
297    return 0;
298}
299
300
301static void
302spi_drop_high_or_non_high (struct stream_prio_iter *iter, int drop_high)
303{
304    uint64_t new_set[ sizeof(iter->spi_set) / sizeof(iter->spi_set[0]) ];
305    unsigned bit, set, n;
306
307    memset(new_set, 0, sizeof(new_set));
308
309    find_and_set_lowest_priority(iter);
310    set = iter->spi_cur_prio >> 6;
311    bit = iter->spi_cur_prio & 0x3F;
312    new_set[set] |= 1ULL << bit;
313
314    if (!have_non_critical_streams(iter))
315    {
316        ++iter->spi_cur_prio;
317        find_and_set_lowest_priority(iter);
318        set = iter->spi_cur_prio >> 6;
319        bit = iter->spi_cur_prio & 0x3F;
320        new_set[set] |= 1ULL << bit;
321    }
322
323    for (n = 0; n < sizeof(new_set) / sizeof(new_set[0]); ++n)
324        if (drop_high)
325            iter->spi_set[n] &= ~new_set[n];
326        else
327            iter->spi_set[n] = new_set[n];
328}
329
330
331void
332lsquic_spi_drop_high (struct stream_prio_iter *iter)
333{
334    spi_drop_high_or_non_high(iter, 1);
335}
336
337
338void
339lsquic_spi_drop_non_high (struct stream_prio_iter *iter)
340{
341    spi_drop_high_or_non_high(iter, 0);
342}
343