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LFU: Initial naive eviction cycle.

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It is possible to get better results by using the pool like in the LRU
case. Also from tests during the morning I believe the current
implementation has issues in the frequency decay function that should
decrease the counter at periodic intervals.
This commit is contained in:
antirez
2016-07-18 13:49:31 +02:00
parent 24dd4a8f04
commit a8e2d0849e
3 changed files with 49 additions and 4 deletions
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36
src/evict.c
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@ -294,6 +294,7 @@ unsigned long LFUDecrAndReturn(robj *o) {
if (LFUTimeElapsed(ldt) > LFU_DECR_INTERVAL && counter) {
if (counter > LFU_INIT_VAL*2) {
counter /= 2;
if (counter < LFU_INIT_VAL*2) counter = LFU_INIT_VAL*2;
} else {
counter--;
}
@ -360,9 +361,7 @@ int freeMemoryIfNeeded(void) {
dict *dict;
dictEntry *de;
if (server.maxmemory_policy == MAXMEMORY_ALLKEYS_LRU ||
server.maxmemory_policy == MAXMEMORY_VOLATILE_LRU)
{
if (server.maxmemory_policy & MAXMEMORY_FLAG_LRU) {
struct evictionPoolEntry *pool = EvictionPoolLRU;
while(bestkey == NULL) {
@ -470,6 +469,37 @@ int freeMemoryIfNeeded(void) {
}
}
/* allkeys-lfu and volatile-lfu */
else if (server.maxmemory_policy & MAXMEMORY_FLAG_LFU) {
long bestfreq = 0; /* Initialized to avoid warning. */
for (i = 0; i < server.dbnum; i++) {
j = (++next_db) % server.dbnum;
db = server.db+j;
dict = (server.maxmemory_policy == MAXMEMORY_ALLKEYS_LFU) ?
db->dict : db->expires;
if (dictSize(dict) != 0) {
for (k = 0; k < server.maxmemory_samples; k++) {
sds thiskey;
long thisfreq;
de = dictGetRandomKey(dict);
thiskey = dictGetKey(de);
robj *o = dictFetchValue(db->dict,thiskey);
thisfreq = LFUDecrAndReturn(o);
/* Keys with a smaller access frequency are
* better candidates for deletion */
if (bestkey == NULL || thisfreq < bestfreq) {
bestkey = thiskey;
bestfreq = thisfreq;
bestdbid = j;
}
}
}
}
}
/* Finally remove the selected key. */
if (bestkey) {
db = server.db+bestdbid;