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mdbx: simplify/speedup scan4seq().

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Леонид Юрьев (Leonid Yuriev) 2022-07-25 12:53:58 +03:00
parent 75d19b5806
commit 268b33cbf7
1 changed files with 82 additions and 50 deletions
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132
src/core.c
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@ -6562,59 +6562,86 @@ __cold static int mdbx_wipe_steady(MDBX_env *env, const txnid_t last_steady) {
return MDBX_SUCCESS;
}
__hot static pgno_t *scan4range(const MDBX_PNL pnl, const unsigned len,
const int num) {
assert(num > 0 && len >= (unsigned)num && len == MDBX_PNL_SIZE(pnl));
__hot static pgno_t *scan4seq(pgno_t *range, const size_t len,
const unsigned seq) {
assert(seq > 0 && len > seq);
#if MDBX_PNL_ASCENDING
const pgno_t *const detent = pnl + len - num;
pgno_t *scan = pnl + 1;
while (likely(scan + 7 <= detent)) {
if (unlikely(scan[num] == *scan + num))
return scan;
if (unlikely(scan[num + 1] == scan[1] + num))
return scan + 1;
if (unlikely(scan[num + 2] == scan[2] + num))
return scan + 2;
if (unlikely(scan[num + 3] == scan[3] + num))
return scan + 3;
if (unlikely(scan[num + 4] == scan[4] + num))
return scan + 4;
if (unlikely(scan[num + 5] == scan[5] + num))
return scan + 5;
if (unlikely(scan[num + 6] == scan[6] + num))
return scan + 6;
if (unlikely(scan[num + 7] == scan[7] + num))
return scan + 7;
scan += 8;
assert(range[-1] == len);
const pgno_t *const detent = range + len - seq;
const ptrdiff_t offset = (ptrdiff_t)seq;
const pgno_t target = (pgno_t)offset;
if (likely(len > seq + 3)) {
do {
const pgno_t diff0 = range[offset + 0] - range[0];
const pgno_t diff1 = range[offset + 1] - range[1];
const pgno_t diff2 = range[offset + 2] - range[2];
const pgno_t diff3 = range[offset + 3] - range[3];
if (diff0 == target)
return range + 0;
if (diff1 == target)
return range + 1;
if (diff2 == target)
return range + 2;
if (diff3 == target)
return range + 3;
range += 4;
} while (range + 3 < detent);
if (range == detent)
return nullptr;
}
for (; scan <= detent; ++scan)
if (scan[num] == *scan + num)
return scan;
do
if (range[offset] - *range == target)
return range;
while (++range < detent);
#else
const pgno_t *const detent = pnl + num;
pgno_t *scan = pnl + len;
while (likely(scan - 7 >= detent)) {
if (unlikely(scan[-num] == *scan + num))
return scan;
if (unlikely(scan[-num - 1] == scan[-1] + num))
return scan - 1;
if (unlikely(scan[-num - 2] == scan[-2] + num))
return scan - 2;
if (unlikely(scan[-num - 3] == scan[-3] + num))
return scan - 3;
if (unlikely(scan[-num - 4] == scan[-4] + num))
return scan - 4;
if (unlikely(scan[-num - 5] == scan[-5] + num))
return scan - 5;
if (unlikely(scan[-num - 6] == scan[-6] + num))
return scan - 6;
if (unlikely(scan[-num - 7] == scan[-7] + num))
return scan - 7;
scan -= 8;
assert(range[-len] == len);
const pgno_t *const detent = range - len + seq;
const ptrdiff_t offset = -(ptrdiff_t)seq;
const pgno_t target = (pgno_t)offset;
if (likely(len > seq + 3)) {
do {
const pgno_t diff0 = range[-0] - range[offset - 0];
const pgno_t diff1 = range[-1] - range[offset - 1];
const pgno_t diff2 = range[-2] - range[offset - 2];
const pgno_t diff3 = range[-3] - range[offset - 3];
/* Смысл вычислений до ветвлений в том, чтобы позволить компилятору
* загружать и вычислять все значения параллельно. */
if (diff0 == target)
return range - 0;
if (diff1 == target)
return range - 1;
if (diff2 == target)
return range - 2;
if (diff3 == target)
return range - 3;
range -= 4;
} while (range > detent + 3);
if (range == detent)
return nullptr;
}
do
if (*range - range[offset] == target)
return range;
while (--range > detent);
#endif /* MDBX_PNL sort-order */
return nullptr;
}
MDBX_MAYBE_UNUSED static const pgno_t *scan4range_checker(const MDBX_PNL pnl,
const unsigned seq) {
size_t begin = MDBX_PNL_ASCENDING ? 1 : MDBX_PNL_SIZE(pnl);
#if MDBX_PNL_ASCENDING
while (seq <= MDBX_PNL_SIZE(pnl) - begin) {
if (pnl[begin + seq] - pnl[begin] == seq)
return pnl + begin;
++begin;
}
#else
while (begin > seq) {
if (pnl[begin - seq] - pnl[begin] == seq)
return pnl + begin;
--begin;
}
for (; scan >= detent; --scan)
if (scan[-num] == *scan + num)
return scan;
#endif /* MDBX_PNL sort-order */
return nullptr;
}
@ -6692,7 +6719,12 @@ static pgr_t page_alloc_slowpath(MDBX_cursor *mc, const pgno_t num, int flags) {
if (!(flags & (MDBX_ALLOC_COALESCE | MDBX_ALLOC_SLOT)) && re_len >= num) {
mdbx_assert(env, MDBX_PNL_LAST(re_list) < txn->mt_next_pgno &&
MDBX_PNL_FIRST(re_list) < txn->mt_next_pgno);
range = scan4range(re_list, re_len, num);
range = re_list + (MDBX_PNL_ASCENDING ? 1 : re_len);
pgno = *range;
if (num == 1)
goto done;
range = scan4seq(range, re_len, num - 1);
mdbx_tassert(txn, range == scan4range_checker(re_list, num - 1));
if (likely(range)) {
pgno = *range;
goto done;