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linux/net/ceph/crush/mapper.c
Ilya Dryomov 958a27658d crush: straw2 bucket type with an efficient 64-bit crush_ln() 
This is an improved straw bucket that correctly avoids any data movement
between items A and B when neither A nor B's weights are changed.  Said
differently, if we adjust the weight of item C (including adding it anew
or removing it completely), we will only see inputs move to or from C,
never between other items in the bucket.

Notably, there is not intermediate scaling factor that needs to be
calculated.  The mapping function is a simple function of the item weights.

The below commits were squashed together into this one (mostly to avoid
adding and then yanking a ~6000 lines worth of crush_ln_table):

- crush: add a straw2 bucket type
- crush: add crush_ln to calculate nature log efficently
- crush: improve straw2 adjustment slightly
- crush: change crush_ln to provide 32 more digits
- crush: fix crush_get_bucket_item_weight and bucket destroy for straw2
- crush/mapper: fix divide-by-0 in straw2
  (with div64_s64() for draw = ln / w and INT64_MIN -> S64_MIN - need
   to create a proper compat.h in ceph.git)

Reflects ceph.git commits 242293c908e923d474910f2b8203fa3b41eb5a53,
                          32a1ead92efcd351822d22a5fc37d159c65c1338,
                          6289912418c4a3597a11778bcf29ed5415117ad9,
                          35fcb04e2945717cf5cfe150b9fa89cb3d2303a1,
                          6445d9ee7290938de1e4ee9563912a6ab6d8ee5f,
                          b5921d55d16796e12d66ad2c4add7305f9ce2353.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
2015-04-22 18:33:43 +03:00

928 lines
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#ifdef __KERNEL__
# include <linux/string.h>
# include <linux/slab.h>
# include <linux/bug.h>
# include <linux/kernel.h>
# ifndef dprintk
# define dprintk(args...)
# endif
#else
# include <string.h>
# include <stdio.h>
# include <stdlib.h>
# include <assert.h>
# define BUG_ON(x) assert(!(x))
# define dprintk(args...) /* printf(args) */
# define kmalloc(x, f) malloc(x)
# define kfree(x) free(x)
#endif
#include <linux/crush/crush.h>
#include <linux/crush/hash.h>
#include "crush_ln_table.h"
/*
* Implement the core CRUSH mapping algorithm.
*/
/**
* crush_find_rule - find a crush_rule id for a given ruleset, type, and size.
* @map: the crush_map
* @ruleset: the storage ruleset id (user defined)
* @type: storage ruleset type (user defined)
* @size: output set size
*/
int crush_find_rule(const struct crush_map *map, int ruleset, int type, int size)
{
__u32 i;
for (i = 0; i < map->max_rules; i++) {
if (map->rules[i] &&
map->rules[i]->mask.ruleset == ruleset &&
map->rules[i]->mask.type == type &&
map->rules[i]->mask.min_size <= size &&
map->rules[i]->mask.max_size >= size)
return i;
}
return -1;
}
/*
* bucket choose methods
*
* For each bucket algorithm, we have a "choose" method that, given a
* crush input @x and replica position (usually, position in output set) @r,
* will produce an item in the bucket.
*/
/*
* Choose based on a random permutation of the bucket.
*
* We used to use some prime number arithmetic to do this, but it
* wasn't very random, and had some other bad behaviors. Instead, we
* calculate an actual random permutation of the bucket members.
* Since this is expensive, we optimize for the r=0 case, which
* captures the vast majority of calls.
*/
static int bucket_perm_choose(struct crush_bucket *bucket,
int x, int r)
{
unsigned int pr = r % bucket->size;
unsigned int i, s;
/* start a new permutation if @x has changed */
if (bucket->perm_x != (__u32)x || bucket->perm_n == 0) {
dprintk("bucket %d new x=%d\n", bucket->id, x);
bucket->perm_x = x;
/* optimize common r=0 case */
if (pr == 0) {
s = crush_hash32_3(bucket->hash, x, bucket->id, 0) %
bucket->size;
bucket->perm[0] = s;
bucket->perm_n = 0xffff; /* magic value, see below */
goto out;
}
for (i = 0; i < bucket->size; i++)
bucket->perm[i] = i;
bucket->perm_n = 0;
} else if (bucket->perm_n == 0xffff) {
/* clean up after the r=0 case above */
for (i = 1; i < bucket->size; i++)
bucket->perm[i] = i;
bucket->perm[bucket->perm[0]] = 0;
bucket->perm_n = 1;
}
/* calculate permutation up to pr */
for (i = 0; i < bucket->perm_n; i++)
dprintk(" perm_choose have %d: %d\n", i, bucket->perm[i]);
while (bucket->perm_n <= pr) {
unsigned int p = bucket->perm_n;
/* no point in swapping the final entry */
if (p < bucket->size - 1) {
i = crush_hash32_3(bucket->hash, x, bucket->id, p) %
(bucket->size - p);
if (i) {
unsigned int t = bucket->perm[p + i];
bucket->perm[p + i] = bucket->perm[p];
bucket->perm[p] = t;
}
dprintk(" perm_choose swap %d with %d\n", p, p+i);
}
bucket->perm_n++;
}
for (i = 0; i < bucket->size; i++)
dprintk(" perm_choose %d: %d\n", i, bucket->perm[i]);
s = bucket->perm[pr];
out:
dprintk(" perm_choose %d sz=%d x=%d r=%d (%d) s=%d\n", bucket->id,
bucket->size, x, r, pr, s);
return bucket->items[s];
}
/* uniform */
static int bucket_uniform_choose(struct crush_bucket_uniform *bucket,
int x, int r)
{
return bucket_perm_choose(&bucket->h, x, r);
}
/* list */
static int bucket_list_choose(struct crush_bucket_list *bucket,
int x, int r)
{
int i;
for (i = bucket->h.size-1; i >= 0; i--) {
__u64 w = crush_hash32_4(bucket->h.hash,x, bucket->h.items[i],
r, bucket->h.id);
w &= 0xffff;
dprintk("list_choose i=%d x=%d r=%d item %d weight %x "
"sw %x rand %llx",
i, x, r, bucket->h.items[i], bucket->item_weights[i],
bucket->sum_weights[i], w);
w *= bucket->sum_weights[i];
w = w >> 16;
/*dprintk(" scaled %llx\n", w);*/
if (w < bucket->item_weights[i])
return bucket->h.items[i];
}
dprintk("bad list sums for bucket %d\n", bucket->h.id);
return bucket->h.items[0];
}
/* (binary) tree */
static int height(int n)
{
int h = 0;
while ((n & 1) == 0) {
h++;
n = n >> 1;
}
return h;
}
static int left(int x)
{
int h = height(x);
return x - (1 << (h-1));
}
static int right(int x)
{
int h = height(x);
return x + (1 << (h-1));
}
static int terminal(int x)
{
return x & 1;
}
static int bucket_tree_choose(struct crush_bucket_tree *bucket,
int x, int r)
{
int n;
__u32 w;
__u64 t;
/* start at root */
n = bucket->num_nodes >> 1;
while (!terminal(n)) {
int l;
/* pick point in [0, w) */
w = bucket->node_weights[n];
t = (__u64)crush_hash32_4(bucket->h.hash, x, n, r,
bucket->h.id) * (__u64)w;
t = t >> 32;
/* descend to the left or right? */
l = left(n);
if (t < bucket->node_weights[l])
n = l;
else
n = right(n);
}
return bucket->h.items[n >> 1];
}
/* straw */
static int bucket_straw_choose(struct crush_bucket_straw *bucket,
int x, int r)
{
__u32 i;
int high = 0;
__u64 high_draw = 0;
__u64 draw;
for (i = 0; i < bucket->h.size; i++) {
draw = crush_hash32_3(bucket->h.hash, x, bucket->h.items[i], r);
draw &= 0xffff;
draw *= bucket->straws[i];
if (i == 0 || draw > high_draw) {
high = i;
high_draw = draw;
}
}
return bucket->h.items[high];
}
// compute 2^44*log2(input+1)
uint64_t crush_ln(unsigned xin)
{
unsigned x=xin, x1;
int iexpon, index1, index2;
uint64_t RH, LH, LL, xl64, result;
x++;
// normalize input
iexpon = 15;
while(!(x&0x18000)) { x<<=1; iexpon--; }
index1 = (x>>8)<<1;
// RH ~ 2^56/index1
RH = __RH_LH_tbl[index1 - 256];
// LH ~ 2^48 * log2(index1/256)
LH = __RH_LH_tbl[index1 + 1 - 256];
// RH*x ~ 2^48 * (2^15 + xf), xf<2^8
xl64 = (int64_t)x * RH;
xl64 >>= 48;
x1 = xl64;
result = iexpon;
result <<= (12 + 32);
index2 = x1 & 0xff;
// LL ~ 2^48*log2(1.0+index2/2^15)
LL = __LL_tbl[index2];
LH = LH + LL;
LH >>= (48-12 - 32);
result += LH;
return result;
}
/*
* straw2
*
* for reference, see:
*
* http://en.wikipedia.org/wiki/Exponential_distribution#Distribution_of_the_minimum_of_exponential_random_variables
*
*/
static int bucket_straw2_choose(struct crush_bucket_straw2 *bucket,
int x, int r)
{
unsigned i, high = 0;
unsigned u;
unsigned w;
__s64 ln, draw, high_draw = 0;
for (i = 0; i < bucket->h.size; i++) {
w = bucket->item_weights[i];
if (w) {
u = crush_hash32_3(bucket->h.hash, x,
bucket->h.items[i], r);
u &= 0xffff;
/*
* for some reason slightly less than 0x10000 produces
* a slightly more accurate distribution... probably a
* rounding effect.
*
* the natural log lookup table maps [0,0xffff]
* (corresponding to real numbers [1/0x10000, 1] to
* [0, 0xffffffffffff] (corresponding to real numbers
* [-11.090355,0]).
*/
ln = crush_ln(u) - 0x1000000000000ll;
/*
* divide by 16.16 fixed-point weight. note
* that the ln value is negative, so a larger
* weight means a larger (less negative) value
* for draw.
*/
draw = div64_s64(ln, w);
} else {
draw = S64_MIN;
}
if (i == 0 || draw > high_draw) {
high = i;
high_draw = draw;
}
}
return bucket->h.items[high];
}
static int crush_bucket_choose(struct crush_bucket *in, int x, int r)
{
dprintk(" crush_bucket_choose %d x=%d r=%d\n", in->id, x, r);
BUG_ON(in->size == 0);
switch (in->alg) {
case CRUSH_BUCKET_UNIFORM:
return bucket_uniform_choose((struct crush_bucket_uniform *)in,
x, r);
case CRUSH_BUCKET_LIST:
return bucket_list_choose((struct crush_bucket_list *)in,
x, r);
case CRUSH_BUCKET_TREE:
return bucket_tree_choose((struct crush_bucket_tree *)in,
x, r);
case CRUSH_BUCKET_STRAW:
return bucket_straw_choose((struct crush_bucket_straw *)in,
x, r);
case CRUSH_BUCKET_STRAW2:
return bucket_straw2_choose((struct crush_bucket_straw2 *)in,
x, r);
default:
dprintk("unknown bucket %d alg %d\n", in->id, in->alg);
return in->items[0];
}
}
/*
* true if device is marked "out" (failed, fully offloaded)
* of the cluster
*/
static int is_out(const struct crush_map *map,
const __u32 *weight, int weight_max,
int item, int x)
{
if (item >= weight_max)
return 1;
if (weight[item] >= 0x10000)
return 0;
if (weight[item] == 0)
return 1;
if ((crush_hash32_2(CRUSH_HASH_RJENKINS1, x, item) & 0xffff)
< weight[item])
return 0;
return 1;
}
/**
* crush_choose_firstn - choose numrep distinct items of given type
* @map: the crush_map
* @bucket: the bucket we are choose an item from
* @x: crush input value
* @numrep: the number of items to choose
* @type: the type of item to choose
* @out: pointer to output vector
* @outpos: our position in that vector
* @out_size: size of the out vector
* @tries: number of attempts to make
* @recurse_tries: number of attempts to have recursive chooseleaf make
* @local_retries: localized retries
* @local_fallback_retries: localized fallback retries
* @recurse_to_leaf: true if we want one device under each item of given type (chooseleaf instead of choose)
* @vary_r: pass r to recursive calls
* @out2: second output vector for leaf items (if @recurse_to_leaf)
* @parent_r: r value passed from the parent
*/
static int crush_choose_firstn(const struct crush_map *map,
struct crush_bucket *bucket,
const __u32 *weight, int weight_max,
int x, int numrep, int type,
int *out, int outpos,
int out_size,
unsigned int tries,
unsigned int recurse_tries,
unsigned int local_retries,
unsigned int local_fallback_retries,
int recurse_to_leaf,
unsigned int vary_r,
int *out2,
int parent_r)
{
int rep;
unsigned int ftotal, flocal;
int retry_descent, retry_bucket, skip_rep;
struct crush_bucket *in = bucket;
int r;
int i;
int item = 0;
int itemtype;
int collide, reject;
int count = out_size;
dprintk("CHOOSE%s bucket %d x %d outpos %d numrep %d tries %d recurse_tries %d local_retries %d local_fallback_retries %d parent_r %d\n",
recurse_to_leaf ? "_LEAF" : "",
bucket->id, x, outpos, numrep,
tries, recurse_tries, local_retries, local_fallback_retries,
parent_r);
for (rep = outpos; rep < numrep && count > 0 ; rep++) {
/* keep trying until we get a non-out, non-colliding item */
ftotal = 0;
skip_rep = 0;
do {
retry_descent = 0;
in = bucket; /* initial bucket */
/* choose through intervening buckets */
flocal = 0;
do {
collide = 0;
retry_bucket = 0;
r = rep + parent_r;
/* r' = r + f_total */
r += ftotal;
/* bucket choose */
if (in->size == 0) {
reject = 1;
goto reject;
}
if (local_fallback_retries > 0 &&
flocal >= (in->size>>1) &&
flocal > local_fallback_retries)
item = bucket_perm_choose(in, x, r);
else
item = crush_bucket_choose(in, x, r);
if (item >= map->max_devices) {
dprintk(" bad item %d\n", item);
skip_rep = 1;
break;
}
/* desired type? */
if (item < 0)
itemtype = map->buckets[-1-item]->type;
else
itemtype = 0;
dprintk(" item %d type %d\n", item, itemtype);
/* keep going? */
if (itemtype != type) {
if (item >= 0 ||
(-1-item) >= map->max_buckets) {
dprintk(" bad item type %d\n", type);
skip_rep = 1;
break;
}
in = map->buckets[-1-item];
retry_bucket = 1;
continue;
}
/* collision? */
for (i = 0; i < outpos; i++) {
if (out[i] == item) {
collide = 1;
break;
}
}
reject = 0;
if (!collide && recurse_to_leaf) {
if (item < 0) {
int sub_r;
if (vary_r)
sub_r = r >> (vary_r-1);
else
sub_r = 0;
if (crush_choose_firstn(map,
map->buckets[-1-item],
weight, weight_max,
x, outpos+1, 0,
out2, outpos, count,
recurse_tries, 0,
local_retries,
local_fallback_retries,
0,
vary_r,
NULL,
sub_r) <= outpos)
/* didn't get leaf */
reject = 1;
} else {
/* we already have a leaf! */
out2[outpos] = item;
}
}
if (!reject) {
/* out? */
if (itemtype == 0)
reject = is_out(map, weight,
weight_max,
item, x);
else
reject = 0;
}
reject:
if (reject || collide) {
ftotal++;
flocal++;
if (collide && flocal <= local_retries)
/* retry locally a few times */
retry_bucket = 1;
else if (local_fallback_retries > 0 &&
flocal <= in->size + local_fallback_retries)
/* exhaustive bucket search */
retry_bucket = 1;
else if (ftotal < tries)
/* then retry descent */
retry_descent = 1;
else
/* else give up */
skip_rep = 1;
dprintk(" reject %d collide %d "
"ftotal %u flocal %u\n",
reject, collide, ftotal,
flocal);
}
} while (retry_bucket);
} while (retry_descent);
if (skip_rep) {
dprintk("skip rep\n");
continue;
}
dprintk("CHOOSE got %d\n", item);
out[outpos] = item;
outpos++;
count--;
}
dprintk("CHOOSE returns %d\n", outpos);
return outpos;
}
/**
* crush_choose_indep: alternative breadth-first positionally stable mapping
*
*/
static void crush_choose_indep(const struct crush_map *map,
struct crush_bucket *bucket,
const __u32 *weight, int weight_max,
int x, int left, int numrep, int type,
int *out, int outpos,
unsigned int tries,
unsigned int recurse_tries,
int recurse_to_leaf,
int *out2,
int parent_r)
{
struct crush_bucket *in = bucket;
int endpos = outpos + left;
int rep;
unsigned int ftotal;
int r;
int i;
int item = 0;
int itemtype;
int collide;
dprintk("CHOOSE%s INDEP bucket %d x %d outpos %d numrep %d\n", recurse_to_leaf ? "_LEAF" : "",
bucket->id, x, outpos, numrep);
/* initially my result is undefined */
for (rep = outpos; rep < endpos; rep++) {
out[rep] = CRUSH_ITEM_UNDEF;
if (out2)
out2[rep] = CRUSH_ITEM_UNDEF;
}
for (ftotal = 0; left > 0 && ftotal < tries; ftotal++) {
for (rep = outpos; rep < endpos; rep++) {
if (out[rep] != CRUSH_ITEM_UNDEF)
continue;
in = bucket; /* initial bucket */
/* choose through intervening buckets */
for (;;) {
/* note: we base the choice on the position
* even in the nested call. that means that
* if the first layer chooses the same bucket
* in a different position, we will tend to
* choose a different item in that bucket.
* this will involve more devices in data
* movement and tend to distribute the load.
*/
r = rep + parent_r;
/* be careful */
if (in->alg == CRUSH_BUCKET_UNIFORM &&
in->size % numrep == 0)
/* r'=r+(n+1)*f_total */
r += (numrep+1) * ftotal;
else
/* r' = r + n*f_total */
r += numrep * ftotal;
/* bucket choose */
if (in->size == 0) {
dprintk(" empty bucket\n");
break;
}
item = crush_bucket_choose(in, x, r);
if (item >= map->max_devices) {
dprintk(" bad item %d\n", item);
out[rep] = CRUSH_ITEM_NONE;
if (out2)
out2[rep] = CRUSH_ITEM_NONE;
left--;
break;
}
/* desired type? */
if (item < 0)
itemtype = map->buckets[-1-item]->type;
else
itemtype = 0;
dprintk(" item %d type %d\n", item, itemtype);
/* keep going? */
if (itemtype != type) {
if (item >= 0 ||
(-1-item) >= map->max_buckets) {
dprintk(" bad item type %d\n", type);
out[rep] = CRUSH_ITEM_NONE;
if (out2)
out2[rep] =
CRUSH_ITEM_NONE;
left--;
break;
}
in = map->buckets[-1-item];
continue;
}
/* collision? */
collide = 0;
for (i = outpos; i < endpos; i++) {
if (out[i] == item) {
collide = 1;
break;
}
}
if (collide)
break;
if (recurse_to_leaf) {
if (item < 0) {
crush_choose_indep(map,
map->buckets[-1-item],
weight, weight_max,
x, 1, numrep, 0,
out2, rep,
recurse_tries, 0,
0, NULL, r);
if (out2[rep] == CRUSH_ITEM_NONE) {
/* placed nothing; no leaf */
break;
}
} else {
/* we already have a leaf! */
out2[rep] = item;
}
}
/* out? */
if (itemtype == 0 &&
is_out(map, weight, weight_max, item, x))
break;
/* yay! */
out[rep] = item;
left--;
break;
}
}
}
for (rep = outpos; rep < endpos; rep++) {
if (out[rep] == CRUSH_ITEM_UNDEF) {
out[rep] = CRUSH_ITEM_NONE;
}
if (out2 && out2[rep] == CRUSH_ITEM_UNDEF) {
out2[rep] = CRUSH_ITEM_NONE;
}
}
}
/**
* crush_do_rule - calculate a mapping with the given input and rule
* @map: the crush_map
* @ruleno: the rule id
* @x: hash input
* @result: pointer to result vector
* @result_max: maximum result size
* @weight: weight vector (for map leaves)
* @weight_max: size of weight vector
* @scratch: scratch vector for private use; must be >= 3 * result_max
*/
int crush_do_rule(const struct crush_map *map,
int ruleno, int x, int *result, int result_max,
const __u32 *weight, int weight_max,
int *scratch)
{
int result_len;
int *a = scratch;
int *b = scratch + result_max;
int *c = scratch + result_max*2;
int recurse_to_leaf;
int *w;
int wsize = 0;
int *o;
int osize;
int *tmp;
struct crush_rule *rule;
__u32 step;
int i, j;
int numrep;
int out_size;
/*
* the original choose_total_tries value was off by one (it
* counted "retries" and not "tries"). add one.
*/
int choose_tries = map->choose_total_tries + 1;
int choose_leaf_tries = 0;
/*
* the local tries values were counted as "retries", though,
* and need no adjustment
*/
int choose_local_retries = map->choose_local_tries;
int choose_local_fallback_retries = map->choose_local_fallback_tries;
int vary_r = map->chooseleaf_vary_r;
if ((__u32)ruleno >= map->max_rules) {
dprintk(" bad ruleno %d\n", ruleno);
return 0;
}
rule = map->rules[ruleno];
result_len = 0;
w = a;
o = b;
for (step = 0; step < rule->len; step++) {
int firstn = 0;
struct crush_rule_step *curstep = &rule->steps[step];
switch (curstep->op) {
case CRUSH_RULE_TAKE:
w[0] = curstep->arg1;
wsize = 1;
break;
case CRUSH_RULE_SET_CHOOSE_TRIES:
if (curstep->arg1 > 0)
choose_tries = curstep->arg1;
break;
case CRUSH_RULE_SET_CHOOSELEAF_TRIES:
if (curstep->arg1 > 0)
choose_leaf_tries = curstep->arg1;
break;
case CRUSH_RULE_SET_CHOOSE_LOCAL_TRIES:
if (curstep->arg1 >= 0)
choose_local_retries = curstep->arg1;
break;
case CRUSH_RULE_SET_CHOOSE_LOCAL_FALLBACK_TRIES:
if (curstep->arg1 >= 0)
choose_local_fallback_retries = curstep->arg1;
break;
case CRUSH_RULE_SET_CHOOSELEAF_VARY_R:
if (curstep->arg1 >= 0)
vary_r = curstep->arg1;
break;
case CRUSH_RULE_CHOOSELEAF_FIRSTN:
case CRUSH_RULE_CHOOSE_FIRSTN:
firstn = 1;
/* fall through */
case CRUSH_RULE_CHOOSELEAF_INDEP:
case CRUSH_RULE_CHOOSE_INDEP:
if (wsize == 0)
break;
recurse_to_leaf =
curstep->op ==
CRUSH_RULE_CHOOSELEAF_FIRSTN ||
curstep->op ==
CRUSH_RULE_CHOOSELEAF_INDEP;
/* reset output */
osize = 0;
for (i = 0; i < wsize; i++) {
/*
* see CRUSH_N, CRUSH_N_MINUS macros.
* basically, numrep <= 0 means relative to
* the provided result_max
*/
numrep = curstep->arg1;
if (numrep <= 0) {
numrep += result_max;
if (numrep <= 0)
continue;
}
j = 0;
if (firstn) {
int recurse_tries;
if (choose_leaf_tries)
recurse_tries =
choose_leaf_tries;
else if (map->chooseleaf_descend_once)
recurse_tries = 1;
else
recurse_tries = choose_tries;
osize += crush_choose_firstn(
map,
map->buckets[-1-w[i]],
weight, weight_max,
x, numrep,
curstep->arg2,
o+osize, j,
result_max-osize,
choose_tries,
recurse_tries,
choose_local_retries,
choose_local_fallback_retries,
recurse_to_leaf,
vary_r,
c+osize,
0);
} else {
out_size = ((numrep < (result_max-osize)) ?
numrep : (result_max-osize));
crush_choose_indep(
map,
map->buckets[-1-w[i]],
weight, weight_max,
x, out_size, numrep,
curstep->arg2,
o+osize, j,
choose_tries,
choose_leaf_tries ?
choose_leaf_tries : 1,
recurse_to_leaf,
c+osize,
0);
osize += out_size;
}
}
if (recurse_to_leaf)
/* copy final _leaf_ values to output set */
memcpy(o, c, osize*sizeof(*o));
/* swap o and w arrays */
tmp = o;
o = w;
w = tmp;
wsize = osize;
break;
case CRUSH_RULE_EMIT:
for (i = 0; i < wsize && result_len < result_max; i++) {
result[result_len] = w[i];
result_len++;
}
wsize = 0;
break;
default:
dprintk(" unknown op %d at step %d\n",
curstep->op, step);
break;
}
}
return result_len;
}
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