Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...
[sfrench/cifs-2.6.git] / net / ceph / crush / mapper.c
1
2 #ifdef __KERNEL__
3 # include <linux/string.h>
4 # include <linux/slab.h>
5 # include <linux/bug.h>
6 # include <linux/kernel.h>
7 # ifndef dprintk
8 #  define dprintk(args...)
9 # endif
10 #else
11 # include <string.h>
12 # include <stdio.h>
13 # include <stdlib.h>
14 # include <assert.h>
15 # define BUG_ON(x) assert(!(x))
16 # define dprintk(args...) /* printf(args) */
17 # define kmalloc(x, f) malloc(x)
18 # define kfree(x) free(x)
19 #endif
20
21 #include <linux/crush/crush.h>
22 #include <linux/crush/hash.h>
23 #include <linux/crush/mapper.h>
24
25 /*
26  * Implement the core CRUSH mapping algorithm.
27  */
28
29 /**
30  * crush_find_rule - find a crush_rule id for a given ruleset, type, and size.
31  * @map: the crush_map
32  * @ruleset: the storage ruleset id (user defined)
33  * @type: storage ruleset type (user defined)
34  * @size: output set size
35  */
36 int crush_find_rule(struct crush_map *map, int ruleset, int type, int size)
37 {
38         int i;
39
40         for (i = 0; i < map->max_rules; i++) {
41                 if (map->rules[i] &&
42                     map->rules[i]->mask.ruleset == ruleset &&
43                     map->rules[i]->mask.type == type &&
44                     map->rules[i]->mask.min_size <= size &&
45                     map->rules[i]->mask.max_size >= size)
46                         return i;
47         }
48         return -1;
49 }
50
51
52 /*
53  * bucket choose methods
54  *
55  * For each bucket algorithm, we have a "choose" method that, given a
56  * crush input @x and replica position (usually, position in output set) @r,
57  * will produce an item in the bucket.
58  */
59
60 /*
61  * Choose based on a random permutation of the bucket.
62  *
63  * We used to use some prime number arithmetic to do this, but it
64  * wasn't very random, and had some other bad behaviors.  Instead, we
65  * calculate an actual random permutation of the bucket members.
66  * Since this is expensive, we optimize for the r=0 case, which
67  * captures the vast majority of calls.
68  */
69 static int bucket_perm_choose(struct crush_bucket *bucket,
70                               int x, int r)
71 {
72         unsigned int pr = r % bucket->size;
73         unsigned int i, s;
74
75         /* start a new permutation if @x has changed */
76         if (bucket->perm_x != x || bucket->perm_n == 0) {
77                 dprintk("bucket %d new x=%d\n", bucket->id, x);
78                 bucket->perm_x = x;
79
80                 /* optimize common r=0 case */
81                 if (pr == 0) {
82                         s = crush_hash32_3(bucket->hash, x, bucket->id, 0) %
83                                 bucket->size;
84                         bucket->perm[0] = s;
85                         bucket->perm_n = 0xffff;   /* magic value, see below */
86                         goto out;
87                 }
88
89                 for (i = 0; i < bucket->size; i++)
90                         bucket->perm[i] = i;
91                 bucket->perm_n = 0;
92         } else if (bucket->perm_n == 0xffff) {
93                 /* clean up after the r=0 case above */
94                 for (i = 1; i < bucket->size; i++)
95                         bucket->perm[i] = i;
96                 bucket->perm[bucket->perm[0]] = 0;
97                 bucket->perm_n = 1;
98         }
99
100         /* calculate permutation up to pr */
101         for (i = 0; i < bucket->perm_n; i++)
102                 dprintk(" perm_choose have %d: %d\n", i, bucket->perm[i]);
103         while (bucket->perm_n <= pr) {
104                 unsigned int p = bucket->perm_n;
105                 /* no point in swapping the final entry */
106                 if (p < bucket->size - 1) {
107                         i = crush_hash32_3(bucket->hash, x, bucket->id, p) %
108                                 (bucket->size - p);
109                         if (i) {
110                                 unsigned int t = bucket->perm[p + i];
111                                 bucket->perm[p + i] = bucket->perm[p];
112                                 bucket->perm[p] = t;
113                         }
114                         dprintk(" perm_choose swap %d with %d\n", p, p+i);
115                 }
116                 bucket->perm_n++;
117         }
118         for (i = 0; i < bucket->size; i++)
119                 dprintk(" perm_choose  %d: %d\n", i, bucket->perm[i]);
120
121         s = bucket->perm[pr];
122 out:
123         dprintk(" perm_choose %d sz=%d x=%d r=%d (%d) s=%d\n", bucket->id,
124                 bucket->size, x, r, pr, s);
125         return bucket->items[s];
126 }
127
128 /* uniform */
129 static int bucket_uniform_choose(struct crush_bucket_uniform *bucket,
130                                  int x, int r)
131 {
132         return bucket_perm_choose(&bucket->h, x, r);
133 }
134
135 /* list */
136 static int bucket_list_choose(struct crush_bucket_list *bucket,
137                               int x, int r)
138 {
139         int i;
140
141         for (i = bucket->h.size-1; i >= 0; i--) {
142                 __u64 w = crush_hash32_4(bucket->h.hash,x, bucket->h.items[i],
143                                          r, bucket->h.id);
144                 w &= 0xffff;
145                 dprintk("list_choose i=%d x=%d r=%d item %d weight %x "
146                         "sw %x rand %llx",
147                         i, x, r, bucket->h.items[i], bucket->item_weights[i],
148                         bucket->sum_weights[i], w);
149                 w *= bucket->sum_weights[i];
150                 w = w >> 16;
151                 /*dprintk(" scaled %llx\n", w);*/
152                 if (w < bucket->item_weights[i])
153                         return bucket->h.items[i];
154         }
155
156         BUG_ON(1);
157         return 0;
158 }
159
160
161 /* (binary) tree */
162 static int height(int n)
163 {
164         int h = 0;
165         while ((n & 1) == 0) {
166                 h++;
167                 n = n >> 1;
168         }
169         return h;
170 }
171
172 static int left(int x)
173 {
174         int h = height(x);
175         return x - (1 << (h-1));
176 }
177
178 static int right(int x)
179 {
180         int h = height(x);
181         return x + (1 << (h-1));
182 }
183
184 static int terminal(int x)
185 {
186         return x & 1;
187 }
188
189 static int bucket_tree_choose(struct crush_bucket_tree *bucket,
190                               int x, int r)
191 {
192         int n, l;
193         __u32 w;
194         __u64 t;
195
196         /* start at root */
197         n = bucket->num_nodes >> 1;
198
199         while (!terminal(n)) {
200                 /* pick point in [0, w) */
201                 w = bucket->node_weights[n];
202                 t = (__u64)crush_hash32_4(bucket->h.hash, x, n, r,
203                                           bucket->h.id) * (__u64)w;
204                 t = t >> 32;
205
206                 /* descend to the left or right? */
207                 l = left(n);
208                 if (t < bucket->node_weights[l])
209                         n = l;
210                 else
211                         n = right(n);
212         }
213
214         return bucket->h.items[n >> 1];
215 }
216
217
218 /* straw */
219
220 static int bucket_straw_choose(struct crush_bucket_straw *bucket,
221                                int x, int r)
222 {
223         int i;
224         int high = 0;
225         __u64 high_draw = 0;
226         __u64 draw;
227
228         for (i = 0; i < bucket->h.size; i++) {
229                 draw = crush_hash32_3(bucket->h.hash, x, bucket->h.items[i], r);
230                 draw &= 0xffff;
231                 draw *= bucket->straws[i];
232                 if (i == 0 || draw > high_draw) {
233                         high = i;
234                         high_draw = draw;
235                 }
236         }
237         return bucket->h.items[high];
238 }
239
240 static int crush_bucket_choose(struct crush_bucket *in, int x, int r)
241 {
242         dprintk(" crush_bucket_choose %d x=%d r=%d\n", in->id, x, r);
243         switch (in->alg) {
244         case CRUSH_BUCKET_UNIFORM:
245                 return bucket_uniform_choose((struct crush_bucket_uniform *)in,
246                                           x, r);
247         case CRUSH_BUCKET_LIST:
248                 return bucket_list_choose((struct crush_bucket_list *)in,
249                                           x, r);
250         case CRUSH_BUCKET_TREE:
251                 return bucket_tree_choose((struct crush_bucket_tree *)in,
252                                           x, r);
253         case CRUSH_BUCKET_STRAW:
254                 return bucket_straw_choose((struct crush_bucket_straw *)in,
255                                            x, r);
256         default:
257                 BUG_ON(1);
258                 return in->items[0];
259         }
260 }
261
262 /*
263  * true if device is marked "out" (failed, fully offloaded)
264  * of the cluster
265  */
266 static int is_out(struct crush_map *map, __u32 *weight, int item, int x)
267 {
268         if (weight[item] >= 0x10000)
269                 return 0;
270         if (weight[item] == 0)
271                 return 1;
272         if ((crush_hash32_2(CRUSH_HASH_RJENKINS1, x, item) & 0xffff)
273             < weight[item])
274                 return 0;
275         return 1;
276 }
277
278 /**
279  * crush_choose - choose numrep distinct items of given type
280  * @map: the crush_map
281  * @bucket: the bucket we are choose an item from
282  * @x: crush input value
283  * @numrep: the number of items to choose
284  * @type: the type of item to choose
285  * @out: pointer to output vector
286  * @outpos: our position in that vector
287  * @firstn: true if choosing "first n" items, false if choosing "indep"
288  * @recurse_to_leaf: true if we want one device under each item of given type
289  * @out2: second output vector for leaf items (if @recurse_to_leaf)
290  */
291 static int crush_choose(struct crush_map *map,
292                         struct crush_bucket *bucket,
293                         __u32 *weight,
294                         int x, int numrep, int type,
295                         int *out, int outpos,
296                         int firstn, int recurse_to_leaf,
297                         int *out2)
298 {
299         int rep;
300         int ftotal, flocal;
301         int retry_descent, retry_bucket, skip_rep;
302         struct crush_bucket *in = bucket;
303         int r;
304         int i;
305         int item = 0;
306         int itemtype;
307         int collide, reject;
308         const int orig_tries = 5; /* attempts before we fall back to search */
309
310         dprintk("CHOOSE%s bucket %d x %d outpos %d numrep %d\n", recurse_to_leaf ? "_LEAF" : "",
311                 bucket->id, x, outpos, numrep);
312
313         for (rep = outpos; rep < numrep; rep++) {
314                 /* keep trying until we get a non-out, non-colliding item */
315                 ftotal = 0;
316                 skip_rep = 0;
317                 do {
318                         retry_descent = 0;
319                         in = bucket;               /* initial bucket */
320
321                         /* choose through intervening buckets */
322                         flocal = 0;
323                         do {
324                                 collide = 0;
325                                 retry_bucket = 0;
326                                 r = rep;
327                                 if (in->alg == CRUSH_BUCKET_UNIFORM) {
328                                         /* be careful */
329                                         if (firstn || numrep >= in->size)
330                                                 /* r' = r + f_total */
331                                                 r += ftotal;
332                                         else if (in->size % numrep == 0)
333                                                 /* r'=r+(n+1)*f_local */
334                                                 r += (numrep+1) *
335                                                         (flocal+ftotal);
336                                         else
337                                                 /* r' = r + n*f_local */
338                                                 r += numrep * (flocal+ftotal);
339                                 } else {
340                                         if (firstn)
341                                                 /* r' = r + f_total */
342                                                 r += ftotal;
343                                         else
344                                                 /* r' = r + n*f_local */
345                                                 r += numrep * (flocal+ftotal);
346                                 }
347
348                                 /* bucket choose */
349                                 if (in->size == 0) {
350                                         reject = 1;
351                                         goto reject;
352                                 }
353                                 if (flocal >= (in->size>>1) &&
354                                     flocal > orig_tries)
355                                         item = bucket_perm_choose(in, x, r);
356                                 else
357                                         item = crush_bucket_choose(in, x, r);
358                                 BUG_ON(item >= map->max_devices);
359
360                                 /* desired type? */
361                                 if (item < 0)
362                                         itemtype = map->buckets[-1-item]->type;
363                                 else
364                                         itemtype = 0;
365                                 dprintk("  item %d type %d\n", item, itemtype);
366
367                                 /* keep going? */
368                                 if (itemtype != type) {
369                                         BUG_ON(item >= 0 ||
370                                                (-1-item) >= map->max_buckets);
371                                         in = map->buckets[-1-item];
372                                         retry_bucket = 1;
373                                         continue;
374                                 }
375
376                                 /* collision? */
377                                 for (i = 0; i < outpos; i++) {
378                                         if (out[i] == item) {
379                                                 collide = 1;
380                                                 break;
381                                         }
382                                 }
383
384                                 reject = 0;
385                                 if (recurse_to_leaf) {
386                                         if (item < 0) {
387                                                 if (crush_choose(map,
388                                                          map->buckets[-1-item],
389                                                          weight,
390                                                          x, outpos+1, 0,
391                                                          out2, outpos,
392                                                          firstn, 0,
393                                                          NULL) <= outpos)
394                                                         /* didn't get leaf */
395                                                         reject = 1;
396                                         } else {
397                                                 /* we already have a leaf! */
398                                                 out2[outpos] = item;
399                                         }
400                                 }
401
402                                 if (!reject) {
403                                         /* out? */
404                                         if (itemtype == 0)
405                                                 reject = is_out(map, weight,
406                                                                 item, x);
407                                         else
408                                                 reject = 0;
409                                 }
410
411 reject:
412                                 if (reject || collide) {
413                                         ftotal++;
414                                         flocal++;
415
416                                         if (collide && flocal < 3)
417                                                 /* retry locally a few times */
418                                                 retry_bucket = 1;
419                                         else if (flocal < in->size + orig_tries)
420                                                 /* exhaustive bucket search */
421                                                 retry_bucket = 1;
422                                         else if (ftotal < 20)
423                                                 /* then retry descent */
424                                                 retry_descent = 1;
425                                         else
426                                                 /* else give up */
427                                                 skip_rep = 1;
428                                         dprintk("  reject %d  collide %d  "
429                                                 "ftotal %d  flocal %d\n",
430                                                 reject, collide, ftotal,
431                                                 flocal);
432                                 }
433                         } while (retry_bucket);
434                 } while (retry_descent);
435
436                 if (skip_rep) {
437                         dprintk("skip rep\n");
438                         continue;
439                 }
440
441                 dprintk("CHOOSE got %d\n", item);
442                 out[outpos] = item;
443                 outpos++;
444         }
445
446         dprintk("CHOOSE returns %d\n", outpos);
447         return outpos;
448 }
449
450
451 /**
452  * crush_do_rule - calculate a mapping with the given input and rule
453  * @map: the crush_map
454  * @ruleno: the rule id
455  * @x: hash input
456  * @result: pointer to result vector
457  * @result_max: maximum result size
458  * @force: force initial replica choice; -1 for none
459  */
460 int crush_do_rule(struct crush_map *map,
461                   int ruleno, int x, int *result, int result_max,
462                   int force, __u32 *weight)
463 {
464         int result_len;
465         int force_context[CRUSH_MAX_DEPTH];
466         int force_pos = -1;
467         int a[CRUSH_MAX_SET];
468         int b[CRUSH_MAX_SET];
469         int c[CRUSH_MAX_SET];
470         int recurse_to_leaf;
471         int *w;
472         int wsize = 0;
473         int *o;
474         int osize;
475         int *tmp;
476         struct crush_rule *rule;
477         int step;
478         int i, j;
479         int numrep;
480         int firstn;
481
482         BUG_ON(ruleno >= map->max_rules);
483
484         rule = map->rules[ruleno];
485         result_len = 0;
486         w = a;
487         o = b;
488
489         /*
490          * determine hierarchical context of force, if any.  note
491          * that this may or may not correspond to the specific types
492          * referenced by the crush rule.
493          */
494         if (force >= 0 &&
495             force < map->max_devices &&
496             map->device_parents[force] != 0 &&
497             !is_out(map, weight, force, x)) {
498                 while (1) {
499                         force_context[++force_pos] = force;
500                         if (force >= 0)
501                                 force = map->device_parents[force];
502                         else
503                                 force = map->bucket_parents[-1-force];
504                         if (force == 0)
505                                 break;
506                 }
507         }
508
509         for (step = 0; step < rule->len; step++) {
510                 firstn = 0;
511                 switch (rule->steps[step].op) {
512                 case CRUSH_RULE_TAKE:
513                         w[0] = rule->steps[step].arg1;
514
515                         /* find position in force_context/hierarchy */
516                         while (force_pos >= 0 &&
517                                force_context[force_pos] != w[0])
518                                 force_pos--;
519                         /* and move past it */
520                         if (force_pos >= 0)
521                                 force_pos--;
522
523                         wsize = 1;
524                         break;
525
526                 case CRUSH_RULE_CHOOSE_LEAF_FIRSTN:
527                 case CRUSH_RULE_CHOOSE_FIRSTN:
528                         firstn = 1;
529                 case CRUSH_RULE_CHOOSE_LEAF_INDEP:
530                 case CRUSH_RULE_CHOOSE_INDEP:
531                         BUG_ON(wsize == 0);
532
533                         recurse_to_leaf =
534                                 rule->steps[step].op ==
535                                  CRUSH_RULE_CHOOSE_LEAF_FIRSTN ||
536                                 rule->steps[step].op ==
537                                 CRUSH_RULE_CHOOSE_LEAF_INDEP;
538
539                         /* reset output */
540                         osize = 0;
541
542                         for (i = 0; i < wsize; i++) {
543                                 /*
544                                  * see CRUSH_N, CRUSH_N_MINUS macros.
545                                  * basically, numrep <= 0 means relative to
546                                  * the provided result_max
547                                  */
548                                 numrep = rule->steps[step].arg1;
549                                 if (numrep <= 0) {
550                                         numrep += result_max;
551                                         if (numrep <= 0)
552                                                 continue;
553                                 }
554                                 j = 0;
555                                 if (osize == 0 && force_pos >= 0) {
556                                         /* skip any intermediate types */
557                                         while (force_pos &&
558                                                force_context[force_pos] < 0 &&
559                                                rule->steps[step].arg2 !=
560                                                map->buckets[-1 -
561                                                force_context[force_pos]]->type)
562                                                 force_pos--;
563                                         o[osize] = force_context[force_pos];
564                                         if (recurse_to_leaf)
565                                                 c[osize] = force_context[0];
566                                         j++;
567                                         force_pos--;
568                                 }
569                                 osize += crush_choose(map,
570                                                       map->buckets[-1-w[i]],
571                                                       weight,
572                                                       x, numrep,
573                                                       rule->steps[step].arg2,
574                                                       o+osize, j,
575                                                       firstn,
576                                                       recurse_to_leaf, c+osize);
577                         }
578
579                         if (recurse_to_leaf)
580                                 /* copy final _leaf_ values to output set */
581                                 memcpy(o, c, osize*sizeof(*o));
582
583                         /* swap t and w arrays */
584                         tmp = o;
585                         o = w;
586                         w = tmp;
587                         wsize = osize;
588                         break;
589
590
591                 case CRUSH_RULE_EMIT:
592                         for (i = 0; i < wsize && result_len < result_max; i++) {
593                                 result[result_len] = w[i];
594                                 result_len++;
595                         }
596                         wsize = 0;
597                         break;
598
599                 default:
600                         BUG_ON(1);
601                 }
602         }
603         return result_len;
604 }
605
606