Message ID | cb04b3ee9392b9930801d2c400f1e64645ba7003.1724405387.git.anatoly.burakov@intel.com (mailing list archive) |
---|---|

State | New |

Delegated to: | Thomas Monjalon |

Headers | |

Series | [v1,1/3] fbarray: rename tests to be more meaningful | |

## Checks

Context | Check | Description |
---|---|---|

ci/checkpatch | warning | coding style issues |

## Commit Message

diff --git a/lib/eal/common/eal_common_fbarray.c b/lib/eal/common/eal_common_fbarray.c index 22b43073c6..d38a43d8d1 100644 --- a/lib/eal/common/eal_common_fbarray.c +++ b/lib/eal/common/eal_common_fbarray.c @@ -117,9 +117,11 @@ find_next_n(const struct rte_fbarray *arr, unsigned int start, unsigned int n, { const struct used_mask *msk = get_used_mask(arr->data, arr->elt_sz, arr->len); - unsigned int msk_idx, lookahead_idx, first, first_mod; + unsigned int msk_idx, first, first_mod; unsigned int last, last_mod; - uint64_t last_msk, ignore_msk; + uint64_t last_msk, first_msk; + unsigned int run_start, left = 0; + bool run_started = false; /* * mask only has granularity of MASK_ALIGN, but start may not be aligned @@ -128,7 +130,7 @@ find_next_n(const struct rte_fbarray *arr, unsigned int start, unsigned int n, */ first = MASK_LEN_TO_IDX(start); first_mod = MASK_LEN_TO_MOD(start); - ignore_msk = ~((1ULL << first_mod) - 1); + first_msk = ~((1ULL << first_mod) - 1); /* array length may not be aligned, so calculate ignore mask for last * mask index. @@ -137,131 +139,120 @@ find_next_n(const struct rte_fbarray *arr, unsigned int start, unsigned int n, last_mod = MASK_LEN_TO_MOD(arr->len); last_msk = ~(UINT64_MAX << last_mod); + left = n; + for (msk_idx = first; msk_idx < msk->n_masks; msk_idx++) { - uint64_t cur_msk, lookahead_msk; - unsigned int run_start, clz, left; - bool found = false; + unsigned int s_idx, clz, need; + uint64_t cur_msk, tmp_msk; + /* - * The process of getting n consecutive bits for arbitrary n is - * a bit involved, but here it is in a nutshell: + * In order to find N consecutive bits for arbitrary N, we need + * to be aware of the following: * - * 1. let n be the number of consecutive bits we're looking for - * 2. check if n can fit in one mask, and if so, do n-1 - * rshift-ands to see if there is an appropriate run inside - * our current mask - * 2a. if we found a run, bail out early - * 2b. if we didn't find a run, proceed - * 3. invert the mask and count leading zeroes (that is, count - * how many consecutive set bits we had starting from the - * end of current mask) as k - * 3a. if k is 0, continue to next mask - * 3b. if k is not 0, we have a potential run - * 4. to satisfy our requirements, next mask must have n-k - * consecutive set bits right at the start, so we will do - * (n-k-1) rshift-ands and check if first bit is set. + * 1. To find N number of consecutive bits within a mask, we + * need to do N-1 rshift-ands and see if we still have set + * bits anywhere in the mask + * 2. N may be larger than mask size, in which case we need to + * do a search in multiple consecutive masks + * 3. For multi-mask search to be meaningful, we need to anchor + * our searches, i.e. first we find a run of M bits at the + * end of current mask, then we look for N-M bits at the + * beginning of next mask (or multiple masks) * - * Step 4 will need to be repeated if (n-k) > MASK_ALIGN until - * we either run out of masks, lose the run, or find what we - * were looking for. + * With all of the above, the algorihm looks as follows: + * + * 1. let N be the number of consecutive bits we're looking for + * 2. if we already started a run, check if we can continue it + * by looking for remainder of N at the beginning of current + * mask + * 3. if we lost a run or if we never had a run, we look for N + * bits anywhere within the current mask (up to mask size, + * we can finish this run in the next mask if N > mask size) + * 4. if we didn't find anything up to this point, check if any + * topmost bits of the mask are set (meaning we can start a + * run and finish it in the next mask) + * 5. at any point in steps 2-4, we may do an early exit due to + * finding what we were looking for, or continue searching + * further */ cur_msk = msk->data[msk_idx]; - left = n; /* if we're looking for free spaces, invert the mask */ if (!used) cur_msk = ~cur_msk; - /* combine current ignore mask with last index ignore mask */ + /* first and last mask may not be aligned */ + if (msk_idx == first) + cur_msk &= first_msk; if (msk_idx == last) - ignore_msk &= last_msk; + cur_msk &= last_msk; - /* if we have an ignore mask, ignore once */ - if (ignore_msk) { - cur_msk &= ignore_msk; - ignore_msk = 0; - } + /* do we have an active previous run? */ + if (run_started) { + /* figure out how many consecutive bits we need here */ + need = RTE_MIN(left, MASK_ALIGN); - /* if n can fit in within a single mask, do a search */ - if (n <= MASK_ALIGN) { - uint64_t tmp_msk = cur_msk; - unsigned int s_idx; - for (s_idx = 0; s_idx < n - 1; s_idx++) + /* see if we get a run of needed length */ + tmp_msk = cur_msk; + for (s_idx = 0; s_idx < need - 1; s_idx++) tmp_msk &= tmp_msk >> 1ULL; - /* we found what we were looking for */ - if (tmp_msk != 0) { - run_start = rte_ctz64(tmp_msk); - return MASK_GET_IDX(msk_idx, run_start); + + /* if first bit is set, we keep the run */ + if (tmp_msk & 1) { + left -= need; + + /* did we find what we were looking for? */ + if (left == 0) + return run_start; + + /* keep looking */ + continue; } + /* we lost the run, reset */ + run_started = false; + left = n; } - /* - * we didn't find our run within the mask, or n > MASK_ALIGN, - * so we're going for plan B. - */ + /* if we're here, we either lost the run or never had it */ + + /* figure out how many consecutive bits we need here */ + need = RTE_MIN(left, MASK_ALIGN); + + /* do a search */ + tmp_msk = cur_msk; + for (s_idx = 0; s_idx < need - 1; s_idx++) + tmp_msk &= tmp_msk >> 1ULL; + + /* have we found something? */ + if (tmp_msk != 0) { + /* figure out where the run started */ + run_start = MASK_GET_IDX(msk_idx, rte_ctz64(tmp_msk)); + run_started = true; + left -= need; + + /* do we need to look further? */ + if (left == 0) + return run_start; + + /* we need to keep looking */ + continue; + } + + /* we didn't find our run within current mask, go for plan B. */ /* count leading zeroes on inverted mask */ - if (~cur_msk == 0) - clz = sizeof(cur_msk) * 8; - else - clz = rte_clz64(~cur_msk); + clz = rte_clz64(~cur_msk); - /* if there aren't any runs at the end either, just continue */ + /* if there aren't any set bits at the end, just continue */ if (clz == 0) continue; - /* we have a partial run at the end, so try looking ahead */ - run_start = MASK_ALIGN - clz; + /* we have a partial run at the end */ + run_start = MASK_GET_IDX(msk_idx, MASK_ALIGN - clz); + run_started = true; left -= clz; - for (lookahead_idx = msk_idx + 1; lookahead_idx < msk->n_masks; - lookahead_idx++) { - unsigned int s_idx, need; - uint64_t first_bit = 1; - - lookahead_msk = msk->data[lookahead_idx]; - - /* if we're looking for free space, invert the mask */ - if (!used) - lookahead_msk = ~lookahead_msk; - - /* figure out how many consecutive bits we need here */ - need = RTE_MIN(left, MASK_ALIGN); - - /* count number of shifts we performed */ - for (s_idx = 0; s_idx < need - 1; s_idx++) { - lookahead_msk &= lookahead_msk >> 1ULL; - /* did we lose the run yet? */ - if ((lookahead_msk & first_bit) == 0) - break; - } - - /* if first bit is not set, we've lost the run */ - if ((lookahead_msk & first_bit) == 0) { - /* - * we've scanned this far, so we know there are - * no runs in the space we've lookahead-scanned - * as well, so skip that on next iteration. - */ - ignore_msk = ~((1ULL << (s_idx + 1)) - 1); - /* outer loop will increment msk_idx so add 1 */ - msk_idx = lookahead_idx - 1; - break; - } - - left -= need; - - /* check if we've found what we were looking for */ - if (left == 0) { - found = true; - break; - } - } - - /* we didn't find anything, so continue */ - if (!found) - continue; - - return MASK_GET_IDX(msk_idx, run_start); + /* we'll figure this out in the next iteration */ } /* we didn't find anything */ rte_errno = used ? ENOENT : ENOSPC;