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Cleanup of entries should not be skipped when using default settings #536

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merged 1 commit into from
Mar 15, 2025
Merged

Cleanup of entries should not be skipped when using default settings #536

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52 changes: 23 additions & 29 deletions apc_cache.c
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Original file line number Diff line number Diff line change
Expand Up @@ -735,8 +735,7 @@ PHP_APCU_API void apc_cache_clear(apc_cache_t* cache)
PHP_APCU_API void apc_cache_default_expunge(apc_cache_t* cache, size_t size)
{
time_t t;
size_t suitable = 0L;
size_t available = 0L;
size_t i;

if (!cache) {
return;
Expand All @@ -751,43 +750,38 @@ PHP_APCU_API void apc_cache_default_expunge(apc_cache_t* cache, size_t size)
return;
}

/* make suitable selection */
suitable = (cache->smart > 0L) ? (size_t) (cache->smart * size) : (size_t) (cache->sma->size/2);

/* gc */
apc_cache_wlocked_gc(cache);

/* get available */
available = apc_sma_get_avail_mem(cache->sma);

/* check that expunge is necessary */
if (available < suitable) {
size_t i;

/* look for junk */
for (i = 0; i < cache->nslots; i++) {
apc_cache_entry_t **entry = &cache->slots[i];
while (*entry) {
if (apc_cache_entry_expired(cache, *entry, t)) {
apc_cache_wlocked_remove_entry(cache, entry);
continue;
}
if (cache->smart > 0L && apc_sma_get_avail_mem(cache->sma) >= (size_t) (cache->smart * size)) {
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Does this even do anything useful? We're only going to call expunge if there is not enough space for size, right?

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Ah no, this is checking for total free size, not available single block. But then doesn't setting smart > 0 still result in expunge being skipped sometimes even though it may have been possible to free up consecutive space?

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Yes, it does and I'd like to change how smart works to address this issue as well. I made a suggestion how smart could be changed in #533. Then I opened this pr (#536) because i wasn't sure if it is a good idea to change the behavior of smart. But finally i think we should do it, because the current implementation seems to be not very useful and will cause unexpected behavior.

If you think it makes sense to change the behavior of smart, I could make the entire change (including smart) here or open a new PR for it. Which do you prefer?

apc_cache_wunlock(cache);
return;
}

/* grab next entry */
entry = &(*entry)->next;
/* look for junk */
for (i = 0; i < cache->nslots; i++) {
apc_cache_entry_t **entry = &cache->slots[i];
while (*entry) {
if (apc_cache_entry_expired(cache, *entry, t)) {
apc_cache_wlocked_remove_entry(cache, entry);
continue;
}
}

/* if the cache now has space, then reset last key */
if (apc_sma_get_avail_size(cache->sma, size)) {
/* wipe lastkey */
memset(&cache->header->lastkey, 0, sizeof(apc_cache_slam_key_t));
} else {
/* with not enough space left in cache, we are forced to expunge */
apc_cache_wlocked_real_expunge(cache);
/* grab next entry */
entry = &(*entry)->next;
}
}

/* if the cache now has space, then reset last key */
if (apc_sma_get_avail_size(cache->sma, size)) {
/* wipe lastkey */
memset(&cache->header->lastkey, 0, sizeof(apc_cache_slam_key_t));
} else {
/* with not enough space left in cache, we are forced to expunge */
apc_cache_wlocked_real_expunge(cache);
}

apc_cache_wunlock(cache);
}
/* }}} */
Expand Down