Linux 3.8-rc7
[cris-mirror.git] / net / ceph / crush / mapper.c
blob35fce755ce103528071d422ca6e9ca2e0faf6a27
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
21 #include <linux/crush/crush.h>
22 #include <linux/crush/hash.h>
23 #include <linux/crush/mapper.h>
26 * Implement the core CRUSH mapping algorithm.
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
36 int crush_find_rule(const struct crush_map *map, int ruleset, int type, int size)
38 __u32 i;
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;
48 return -1;
53 * bucket choose methods
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.
61 * Choose based on a random permutation of the bucket.
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.
69 static int bucket_perm_choose(struct crush_bucket *bucket,
70 int x, int r)
72 unsigned int pr = r % bucket->size;
73 unsigned int i, s;
75 /* start a new permutation if @x has changed */
76 if (bucket->perm_x != (__u32)x || bucket->perm_n == 0) {
77 dprintk("bucket %d new x=%d\n", bucket->id, x);
78 bucket->perm_x = x;
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;
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;
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;
114 dprintk(" perm_choose swap %d with %d\n", p, p+i);
116 bucket->perm_n++;
118 for (i = 0; i < bucket->size; i++)
119 dprintk(" perm_choose %d: %d\n", i, bucket->perm[i]);
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];
128 /* uniform */
129 static int bucket_uniform_choose(struct crush_bucket_uniform *bucket,
130 int x, int r)
132 return bucket_perm_choose(&bucket->h, x, r);
135 /* list */
136 static int bucket_list_choose(struct crush_bucket_list *bucket,
137 int x, int r)
139 int i;
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];
156 dprintk("bad list sums for bucket %d\n", bucket->h.id);
157 return bucket->h.items[0];
161 /* (binary) tree */
162 static int height(int n)
164 int h = 0;
165 while ((n & 1) == 0) {
166 h++;
167 n = n >> 1;
169 return h;
172 static int left(int x)
174 int h = height(x);
175 return x - (1 << (h-1));
178 static int right(int x)
180 int h = height(x);
181 return x + (1 << (h-1));
184 static int terminal(int x)
186 return x & 1;
189 static int bucket_tree_choose(struct crush_bucket_tree *bucket,
190 int x, int r)
192 int n, l;
193 __u32 w;
194 __u64 t;
196 /* start at root */
197 n = bucket->num_nodes >> 1;
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;
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);
214 return bucket->h.items[n >> 1];
218 /* straw */
220 static int bucket_straw_choose(struct crush_bucket_straw *bucket,
221 int x, int r)
223 __u32 i;
224 int high = 0;
225 __u64 high_draw = 0;
226 __u64 draw;
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;
237 return bucket->h.items[high];
240 static int crush_bucket_choose(struct crush_bucket *in, int x, int r)
242 dprintk(" crush_bucket_choose %d x=%d r=%d\n", in->id, x, r);
243 BUG_ON(in->size == 0);
244 switch (in->alg) {
245 case CRUSH_BUCKET_UNIFORM:
246 return bucket_uniform_choose((struct crush_bucket_uniform *)in,
247 x, r);
248 case CRUSH_BUCKET_LIST:
249 return bucket_list_choose((struct crush_bucket_list *)in,
250 x, r);
251 case CRUSH_BUCKET_TREE:
252 return bucket_tree_choose((struct crush_bucket_tree *)in,
253 x, r);
254 case CRUSH_BUCKET_STRAW:
255 return bucket_straw_choose((struct crush_bucket_straw *)in,
256 x, r);
257 default:
258 dprintk("unknown bucket %d alg %d\n", in->id, in->alg);
259 return in->items[0];
264 * true if device is marked "out" (failed, fully offloaded)
265 * of the cluster
267 static int is_out(const struct crush_map *map, const __u32 *weight, int item, int x)
269 if (weight[item] >= 0x10000)
270 return 0;
271 if (weight[item] == 0)
272 return 1;
273 if ((crush_hash32_2(CRUSH_HASH_RJENKINS1, x, item) & 0xffff)
274 < weight[item])
275 return 0;
276 return 1;
280 * crush_choose - choose numrep distinct items of given type
281 * @map: the crush_map
282 * @bucket: the bucket we are choose an item from
283 * @x: crush input value
284 * @numrep: the number of items to choose
285 * @type: the type of item to choose
286 * @out: pointer to output vector
287 * @outpos: our position in that vector
288 * @firstn: true if choosing "first n" items, false if choosing "indep"
289 * @recurse_to_leaf: true if we want one device under each item of given type
290 * @out2: second output vector for leaf items (if @recurse_to_leaf)
292 static int crush_choose(const struct crush_map *map,
293 struct crush_bucket *bucket,
294 const __u32 *weight,
295 int x, int numrep, int type,
296 int *out, int outpos,
297 int firstn, int recurse_to_leaf,
298 int *out2)
300 int rep;
301 unsigned int ftotal, flocal;
302 int retry_descent, retry_bucket, skip_rep;
303 struct crush_bucket *in = bucket;
304 int r;
305 int i;
306 int item = 0;
307 int itemtype;
308 int collide, reject;
310 dprintk("CHOOSE%s bucket %d x %d outpos %d numrep %d\n", recurse_to_leaf ? "_LEAF" : "",
311 bucket->id, x, outpos, numrep);
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 */
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 || (__u32)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);
348 /* bucket choose */
349 if (in->size == 0) {
350 reject = 1;
351 goto reject;
353 if (map->choose_local_fallback_tries > 0 &&
354 flocal >= (in->size>>1) &&
355 flocal > map->choose_local_fallback_tries)
356 item = bucket_perm_choose(in, x, r);
357 else
358 item = crush_bucket_choose(in, x, r);
359 if (item >= map->max_devices) {
360 dprintk(" bad item %d\n", item);
361 skip_rep = 1;
362 break;
365 /* desired type? */
366 if (item < 0)
367 itemtype = map->buckets[-1-item]->type;
368 else
369 itemtype = 0;
370 dprintk(" item %d type %d\n", item, itemtype);
372 /* keep going? */
373 if (itemtype != type) {
374 if (item >= 0 ||
375 (-1-item) >= map->max_buckets) {
376 dprintk(" bad item type %d\n", type);
377 skip_rep = 1;
378 break;
380 in = map->buckets[-1-item];
381 retry_bucket = 1;
382 continue;
385 /* collision? */
386 for (i = 0; i < outpos; i++) {
387 if (out[i] == item) {
388 collide = 1;
389 break;
393 reject = 0;
394 if (recurse_to_leaf) {
395 if (item < 0) {
396 if (crush_choose(map,
397 map->buckets[-1-item],
398 weight,
399 x, outpos+1, 0,
400 out2, outpos,
401 firstn, 0,
402 NULL) <= outpos)
403 /* didn't get leaf */
404 reject = 1;
405 } else {
406 /* we already have a leaf! */
407 out2[outpos] = item;
411 if (!reject) {
412 /* out? */
413 if (itemtype == 0)
414 reject = is_out(map, weight,
415 item, x);
416 else
417 reject = 0;
420 reject:
421 if (reject || collide) {
422 ftotal++;
423 flocal++;
425 if (collide && flocal <= map->choose_local_tries)
426 /* retry locally a few times */
427 retry_bucket = 1;
428 else if (map->choose_local_fallback_tries > 0 &&
429 flocal <= in->size + map->choose_local_fallback_tries)
430 /* exhaustive bucket search */
431 retry_bucket = 1;
432 else if (ftotal <= map->choose_total_tries)
433 /* then retry descent */
434 retry_descent = 1;
435 else
436 /* else give up */
437 skip_rep = 1;
438 dprintk(" reject %d collide %d "
439 "ftotal %u flocal %u\n",
440 reject, collide, ftotal,
441 flocal);
443 } while (retry_bucket);
444 } while (retry_descent);
446 if (skip_rep) {
447 dprintk("skip rep\n");
448 continue;
451 dprintk("CHOOSE got %d\n", item);
452 out[outpos] = item;
453 outpos++;
456 dprintk("CHOOSE returns %d\n", outpos);
457 return outpos;
462 * crush_do_rule - calculate a mapping with the given input and rule
463 * @map: the crush_map
464 * @ruleno: the rule id
465 * @x: hash input
466 * @result: pointer to result vector
467 * @result_max: maximum result size
469 int crush_do_rule(const struct crush_map *map,
470 int ruleno, int x, int *result, int result_max,
471 const __u32 *weight)
473 int result_len;
474 int a[CRUSH_MAX_SET];
475 int b[CRUSH_MAX_SET];
476 int c[CRUSH_MAX_SET];
477 int recurse_to_leaf;
478 int *w;
479 int wsize = 0;
480 int *o;
481 int osize;
482 int *tmp;
483 struct crush_rule *rule;
484 __u32 step;
485 int i, j;
486 int numrep;
487 int firstn;
489 if ((__u32)ruleno >= map->max_rules) {
490 dprintk(" bad ruleno %d\n", ruleno);
491 return 0;
494 rule = map->rules[ruleno];
495 result_len = 0;
496 w = a;
497 o = b;
499 for (step = 0; step < rule->len; step++) {
500 struct crush_rule_step *curstep = &rule->steps[step];
502 firstn = 0;
503 switch (curstep->op) {
504 case CRUSH_RULE_TAKE:
505 w[0] = curstep->arg1;
506 wsize = 1;
507 break;
509 case CRUSH_RULE_CHOOSE_LEAF_FIRSTN:
510 case CRUSH_RULE_CHOOSE_FIRSTN:
511 firstn = 1;
512 /* fall through */
513 case CRUSH_RULE_CHOOSE_LEAF_INDEP:
514 case CRUSH_RULE_CHOOSE_INDEP:
515 if (wsize == 0)
516 break;
518 recurse_to_leaf =
519 curstep->op ==
520 CRUSH_RULE_CHOOSE_LEAF_FIRSTN ||
521 curstep->op ==
522 CRUSH_RULE_CHOOSE_LEAF_INDEP;
524 /* reset output */
525 osize = 0;
527 for (i = 0; i < wsize; i++) {
529 * see CRUSH_N, CRUSH_N_MINUS macros.
530 * basically, numrep <= 0 means relative to
531 * the provided result_max
533 numrep = curstep->arg1;
534 if (numrep <= 0) {
535 numrep += result_max;
536 if (numrep <= 0)
537 continue;
539 j = 0;
540 osize += crush_choose(map,
541 map->buckets[-1-w[i]],
542 weight,
543 x, numrep,
544 curstep->arg2,
545 o+osize, j,
546 firstn,
547 recurse_to_leaf, c+osize);
550 if (recurse_to_leaf)
551 /* copy final _leaf_ values to output set */
552 memcpy(o, c, osize*sizeof(*o));
554 /* swap t and w arrays */
555 tmp = o;
556 o = w;
557 w = tmp;
558 wsize = osize;
559 break;
562 case CRUSH_RULE_EMIT:
563 for (i = 0; i < wsize && result_len < result_max; i++) {
564 result[result_len] = w[i];
565 result_len++;
567 wsize = 0;
568 break;
570 default:
571 dprintk(" unknown op %d at step %d\n",
572 curstep->op, step);
573 break;
576 return result_len;