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Revise LRU trim logic #475

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Revise LRU trim logic #475

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5785544
trim volatile
Nov 13, 2023
ff02c46
merge
Nov 13, 2023
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35 changes: 27 additions & 8 deletions BitFaster.Caching/Lru/ConcurrentLruCore.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -513,40 +513,59 @@ private void TrimLiveItems(int itemsRemoved, int itemCount, ItemRemovedReason re
int trimWarmAttempts = 0;
int maxWarmHotAttempts = (this.capacity.Warm * 2) + this.capacity.Hot;

int warmCount = Volatile.Read(ref this.counter.warm);
int coldCount = Volatile.Read(ref this.counter.cold);

while (itemsRemoved < itemCount && trimWarmAttempts < maxWarmHotAttempts)
{
if (Volatile.Read(ref this.counter.cold) > 0)
if (coldCount > 0)
{
if (TryRemoveCold(reason) == (ItemDestination.Remove, 0))
{
itemsRemoved++;
coldCount--;
trimWarmAttempts = 0;
}

TrimWarmOrHot(reason);
TrimWarmOrHot(reason, ref warmCount, ref coldCount);
}
else
{
TrimWarmOrHot(reason);
TrimWarmOrHot(reason, ref warmCount, ref coldCount);
trimWarmAttempts++;
}
}

if (Volatile.Read(ref this.counter.warm) < this.capacity.Warm)
if (warmCount < this.capacity.Warm)
{
Volatile.Write(ref this.isWarm, false);
}
}

private void TrimWarmOrHot(ItemRemovedReason reason)
private void TrimWarmOrHot(ItemRemovedReason reason, ref int warmCount, ref int coldCount)
{
if (Volatile.Read(ref this.counter.warm) > 0)
if (warmCount > 0)
{
CycleWarmUnchecked(reason);
var (dest, count) = CycleWarmUnchecked(reason);
warmCount--;
UpdateCount(ref warmCount, ref coldCount, dest, count);
}
else if (Volatile.Read(ref this.counter.hot) > 0)
{
CycleHotUnchecked(reason);
var (dest, count) = CycleHotUnchecked(reason);
UpdateCount(ref warmCount, ref coldCount, dest, count);
}

void UpdateCount(ref int warmCount, ref int coldCount, ItemDestination dest, int count)
{
if (dest == ItemDestination.Cold)
{
coldCount = count;
}
else if (dest == ItemDestination.Warm)
{
warmCount = count;
}
}
}

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