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Optimize dictTypeResizeAllowed to avoid mistaken OOM judgement. (#12950)

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When doing dict resizing, dictTypeResizeAllowed is used to judge whether
the new allocated memory for rehashing would cause OOM.

However when shrinking, we alloc `_dictNextExp(d->ht_used[0])` bytes of
memory, while in `dictTypeResizeAllowed` we still use
`_dictNextExp(d->ht_used[0]+1)` as the new allocated memory size. This
will overestimate the memory used by shrinking at special conditions,
causing a false OOM judgement.
This commit is contained in:
Chen Tianjie 2024-01-18 22:35:12 +08:00 committed by GitHub
parent 1c7eb0ad37
commit f81c3fd89e
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GPG Key ID: B5690EEEBB952194
1 changed files with 6 additions and 6 deletions
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12
src/dict.c
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@ -1421,12 +1421,12 @@ unsigned long dictScanDefrag(dict *d,
/* ------------------------- private functions ------------------------------ */
/* Because we may need to allocate huge memory chunk at once when dict
* expands, we will check this allocation is allowed or not if the dict
* type has expandAllowed member function. */
static int dictTypeResizeAllowed(dict *d) {
* resizes, we will check this allocation is allowed or not if the dict
* type has resizeAllowed member function. */
static int dictTypeResizeAllowed(dict *d, size_t size) {
if (d->type->resizeAllowed == NULL) return 1;
return d->type->resizeAllowed(
DICTHT_SIZE(_dictNextExp(d->ht_used[0] + 1)) * sizeof(dictEntry*),
DICTHT_SIZE(_dictNextExp(size)) * sizeof(dictEntry*),
(double)d->ht_used[0] / DICTHT_SIZE(d->ht_size_exp[0]));
}
@ -1454,7 +1454,7 @@ static void _dictExpandIfNeeded(dict *d)
(dict_can_resize != DICT_RESIZE_FORBID &&
d->ht_used[0] >= dict_force_resize_ratio * DICTHT_SIZE(d->ht_size_exp[0])))
{
if (!dictTypeResizeAllowed(d))
if (!dictTypeResizeAllowed(d, d->ht_used[0] + 1))
return;
dictExpand(d, d->ht_used[0] + 1);
}
@ -1479,7 +1479,7 @@ static void _dictShrinkIfNeeded(dict *d)
(dict_can_resize != DICT_RESIZE_FORBID &&
d->ht_used[0] * 100 * dict_force_resize_ratio <= HASHTABLE_MIN_FILL * DICTHT_SIZE(d->ht_size_exp[0])))
{
if (!dictTypeResizeAllowed(d))
if (!dictTypeResizeAllowed(d, d->ht_used[0]))
return;
dictShrink(d, d->ht_used[0]);
}