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LFU: Fix LFUDecrAndReturn() to just decrement. 

Splitting the popularity in half actually just needs decrementing the
counter because the counter is logarithmic.
This commit is contained in:
antirez 2017-11-27 19:04:58 +01:00
parent 9f131c9a89
commit 06ca9d6839
1 changed files with 3 additions and 13 deletions
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16
src/evict.c
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@ -335,19 +335,9 @@ uint8_t LFULogIncr(uint8_t counter) {
unsigned long LFUDecrAndReturn(robj *o) {
unsigned long ldt = o->lru >> 8;
unsigned long counter = o->lru & 255;
long halve_times = server.lfu_decay_time ? LFUTimeElapsed(ldt) / server.lfu_decay_time : 0;
if (halve_times > 0 && counter) {
if (halve_times == 1) {
if (counter > LFU_INIT_VAL*2) {
counter /= 2;
if (counter < LFU_INIT_VAL*2) counter = LFU_INIT_VAL*2;
} else {
counter--;
}
} else {
counter = counter >> halve_times;
}
}
unsigned long num_periods = server.lfu_decay_time ? LFUTimeElapsed(ldt) / server.lfu_decay_time : 0;
if (num_periods)
counter = (num_periods > counter) ? 0 : counter - num_periods;
return counter;
}