private static void doShrinkCycle()
{
var baselines = CalculateBaselines();
// sort all caches that have existed and not been grown for a full shrink cycle by score ascending
// score = (1 + impact/baselineImpact) / (1 + cost/baselineCost)
// calculate forever and this cycle and take the higher (better) answer
var shrinkCandidates = (from hitInfo in Nrdo.GetCacheHitInfoUnsorted()
where hitInfo.Cache.IsEnabled && hitInfo.lastShrinkCycleStats != null && (hitInfo.lastGrownStats == null || hitInfo.lastGrownStats.LatestGlobalStats.LatestOperationStamp < hitInfo.lastShrinkCycleStats.LatestGlobalStats.LatestOperationStamp)
let stats = hitInfo.CacheStats.ToNow()
let thisCycle = stats.Since(hitInfo.lastShrinkCycleStats)
let sinceLastShrink = stats.Since(hitInfo.lastShrunkStats)
let globalScore = (1 + Portion.SafeRatio(stats.Impact, baselines.Baseline.Impact)) / (1 + sinceLastShrink.CumulativeCost / baselines.Baseline.Cost)
let cycleScore = (1 + Portion.SafeRatio(thisCycle.Impact, baselines.CycleBaseline.Impact)) - (1 + thisCycle.CumulativeCost / baselines.CycleBaseline.Cost)
let score = Portion.Max(globalScore, cycleScore)
orderby score ascending
select new { hitInfo, score }).ToList();
// shrink the first 1/4 of the caches in that list as long as their score is strictly < 100%
shrinkCandidates = shrinkCandidates.Take(shrinkCandidates.Count / 4).Where(c => c.score < Portion.Complete).ToList();
foreach (var candidate in shrinkCandidates)
{
if (candidate.hitInfo.IsList)
{
var listCache = (IListCache)candidate.hitInfo.Cache;
if (listCache.Capacity == 0 && listCache.ItemCapacity == 1)
{
listCache.Clear();
}
else if (listCache.ItemCapacity == 0 && listCache.Capacity == 1)
{
listCache.ItemCapacity = (int)candidate.hitInfo.CacheStats.AverageResultItems + 1;
listCache.Capacity = 0;
}
else
{
listCache.Capacity = listCache.Capacity * 3 / 4;
listCache.ItemCapacity = listCache.ItemCapacity * 3 / 4;
}
}
else
{
if (candidate.hitInfo.Cache.Capacity <= 1)
{
candidate.hitInfo.Cache.Clear();
}
else
{
candidate.hitInfo.Cache.Capacity = candidate.hitInfo.Cache.Capacity * 3 / 4;
}
}
candidate.hitInfo.shrinkCount++;
candidate.hitInfo.lastShrunkStats = candidate.hitInfo.CacheStats.ToNow();
}
// store last shrink cycle info for each individual cache
lastShrinkCycleStats = globalStats.ToNow();
foreach (var hitInfo in Nrdo.GetCacheHitInfoUnsorted())
{
hitInfo.lastShrinkCycleStats = hitInfo.CacheStats.ToNow();
}
}
private static void doGrowPulse()
{
// - Grow caches where ImpactGainHybrid is "high" both as a percentage of total DB time and in
// absolute value as measured over the period *since this cache was last rebalanced*.
// Algorithm:
// - Take all caches where ImpactGainHybrid[since last grown] is greater than zero
// - Sort by ImpactGainHybrid[since last grown]/Nrdo.TotalQueryTime[since last grown]
// - Take all caches that existed at last cycle, haven't grown since then, and where ImpactGainHybrid[this cycle] is greater than zero
// (using this pulse would be better but we don't have this cache's stats for that)
// - Sort by ImpactGainHybrid[this cycle]/Nrdo.TotalQueryTime[this cycle]
// - Grow any caches that are in the top 50% of either list and also have ImpactGainHybrid[since last grown] > CacheGrowThreshold
var growCandidates = (from hitInfo in Nrdo.GetCacheHitInfoUnsorted()
let stats = hitInfo.CacheStats.ToNow()
let sinceGrow = stats.Since(hitInfo.lastGrownStats)
let gainSinceGrow = sinceGrow.PotentialImpactGainHybrid
where gainSinceGrow > TimeSpan.Zero
let ratioSinceGrow = Portion.SafeRatio(gainSinceGrow, sinceGrow.LatestGlobalStats.TotalQueryTime)
let thisCycle = hitInfo.lastShrinkCycleStats == null ||
(hitInfo.lastGrownStats != null && hitInfo.lastGrownStats.LatestGlobalStats.LatestOperationStamp >= hitInfo.lastShrinkCycleStats.LatestGlobalStats.LatestOperationStamp)
? null : stats.Since(hitInfo.lastShrinkCycleStats)
let gainThisCycle = thisCycle == null ? TimeSpan.Zero : thisCycle.PotentialImpactGainHybrid
let ratioThisCycle = thisCycle == null ? Portion.Zero : Portion.SafeRatio(gainThisCycle, thisCycle.LatestGlobalStats.TotalQueryTime)
select new
{
hitInfo,
stats,
sinceGrow,
gainSinceGrow,
ratioSinceGrow,
thisCycle,
gainThisCycle,
ratioThisCycle
}).ToList();
if (!growCandidates.Any())
{
return;
}
var sinceGrowRatioLimit = growCandidates.OrderBy(c => c.ratioSinceGrow).ElementAt(growCandidates.Count / 2).ratioSinceGrow;
var cycleCandidates = growCandidates.Where(c => c.gainThisCycle > TimeSpan.Zero).ToList();
var cycleRatioLimit = cycleCandidates.Any() ? cycleCandidates.OrderBy(c => c.ratioThisCycle).ElementAt(cycleCandidates.Count / 2).ratioThisCycle : Portion.Complete;
var growCaches = from cache in growCandidates
where cache.gainSinceGrow > CacheGrowThreshold &&
(cache.ratioSinceGrow >= sinceGrowRatioLimit ||
(cache.gainThisCycle > TimeSpan.Zero && cache.ratioThisCycle >= cycleRatioLimit))
select cache;
foreach (var candidate in growCaches)
{
// - Calculate GrowthFactor: 1 + Max(NonHitsOverCapacity / TotalQueries, 0.2)
var growthFactor = 1 + Math.Max((double)candidate.sinceGrow.NonHitsOverCapacity / candidate.sinceGrow.TotalQueries, 0.2);
// - For non-list caches, Capacity = Max(Capacity * GrowthFactor, Capacity + 2)
if (!candidate.hitInfo.IsList)
{
var targetCapacity = Math.Max((int)(candidate.hitInfo.Cache.Capacity * growthFactor), candidate.hitInfo.Cache.Capacity + 2);
candidate.hitInfo.Cache.Capacity = Math.Min(targetCapacity, Nrdo.MaxCacheCapacity);
}
else
{
var listSinceGrow = candidate.sinceGrow.ListStats;
var listCache = (IListCache)candidate.hitInfo.Cache;
// - For list caches,
// - Calculate PotentialCost: Max(PeakItemCount, ItemCapacity, Capacity * WeightedResultItems)
var potentialCost = Math.Max(Math.Max(listCache.ItemCapacity, listCache.PeakItemCount), listCache.Capacity * candidate.sinceGrow.WeightedResultItems);
// - Calculate TargetCost = GrowthFactor * Max(PotentialCost, WeightedResultItems)
var targetCost = Math.Min(growthFactor * Math.Max(potentialCost, candidate.hitInfo.CacheStats.WeightedResultItems), Nrdo.MaxCacheCapacity);
// - Calculate TargetCapacity = Max(TargetCost / WeightedResultItems, Capacity + 1)
var targetCapacity = Math.Max((int)(targetCost / candidate.hitInfo.CacheStats.WeightedResultItems), listCache.Capacity + 1);
// - If ItemCapacity < TargetCapacity * AvgResultItems or (Capacity = 0 and Skipped = 0)
if (listCache.ItemCapacity < targetCapacity * candidate.hitInfo.CacheStats.AverageResultItems ||
(listCache.Capacity == 0 && listSinceGrow.Skipped == 0))
{
// - Set ItemCapacity = Max(TargetCost, ItemCapacity + 2)
listCache.ItemCapacity = Math.Max((int)targetCost, listCache.ItemCapacity + 2);
}
else
{
// - Set Capacity = TargetCapacity and ItemCapacity = TargetCapacity * AvgResultItems
listCache.Capacity = targetCapacity;
listCache.ItemCapacity = (int)(targetCapacity * candidate.hitInfo.CacheStats.AverageResultItems);
}
}
candidate.hitInfo.growCount++;
candidate.hitInfo.lastGrownStats = candidate.hitInfo.CacheStats.ToNow();
}
}
