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Make max hashLookup load factor (for tiering) greater than max 'normal'

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load factor (0.66), to avoid tiering due to natural variance in segment
load. Account non-tiered segments percentile
This commit is contained in:
leventov
2015-12-10 17:43:47 +03:00
parent af2793a8f5
commit 8abe53912a
6 changed files with 32 additions and 8 deletions
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src/main/java/net/openhft/chronicle/hash/impl/CompactOffHeapLinearHashTable.java
+11 -6
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@@ -26,7 +26,14 @@ public abstract class CompactOffHeapLinearHashTable {
// to fit 64 bits per slot.
public static final int MAX_TIER_CHUNKS = 1 << 30;
public static final int MAX_TIER_ENTRIES = 1 << 29;
public static final double MAX_LOAD_FACTOR = .2/.3;
/** Normally, hashLookup capacity is chosen so that the lf varies from 1/3 to 2/3, at most */
public static final double MAX_UPPER_BOUND_LOAD_FACTOR = .2/.3;
/**
* If average key/value sizes are configured wrong, and Chronicle Hash bloats up (size grows
* beyond configured .entries()), hashLookup might become too full. Stop insertion and trigger
* segment tiering, when hashLookup load factor > 0.8, because collision chains become too long.
*/
public static final double MAX_LOAD_FACTOR = 0.8;
public static int valueBits(long actualChunksPerSegment) {
@@ -56,12 +63,10 @@ public abstract class CompactOffHeapLinearHashTable {
public static long capacityFor(long entriesPerSegment) {
if (entriesPerSegment < 0L)
throw new IllegalArgumentException("entriesPerSegment should be positive");
throw new AssertionError("entriesPerSegment should be positive");
long capacity = Maths.nextPower2(entriesPerSegment, 64L);
if (((double) entriesPerSegment) / (double) capacity > MAX_LOAD_FACTOR) {
// hash lookup shouldn't be too dense
capacity <<= 1L;
}
if (entriesPerSegment > MAX_UPPER_BOUND_LOAD_FACTOR * capacity)
capacity *= 2;
return capacity;
}