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perf: de-parallelize upscale ancestor lookup to avoid thread-pool starvation #264

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perf: de-parallelize upscale ancestor lookup to avoid thread-pool starvation #264

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37 changes: 9 additions & 28 deletions MergerLogic/DataTypes/Data.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,6 @@
using MergerLogic.Utils;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using System.Collections.Concurrent;
using System.Diagnostics;
using System.Reflection;
using System.Runtime.Serialization;
Expand Down Expand Up @@ -215,36 +214,18 @@ protected virtual Extent GetExtent()
coordsList.Add(new Coord(i, baseTileX, baseTileY));
}

// Async method to request all tiles that can be used for "upscale" concurrently
var getUpscaleTiles = async delegate (Coord[] coordsArray)
// coordsList runs highest zoom first, so the first hit is the closest ancestor to upscale from.
foreach (Coord coord in coordsList)
{
ConcurrentDictionary<int, Tile?> zOrderToTileDictionary = new ConcurrentDictionary<int, Tile?>();
// get all tiles concurrently
await Parallel.ForEachAsync(coordsArray, async (coord, cancellationToken) =>
Tile? tile = this.Utils.GetTile(coord.Z, coord.X, coord.Y);
if (tile != null)
{
await Task.Run(() =>
{
Tile? tile = this.Utils.GetTile(coord.Z, coord.X, coord.Y);
if (tile != null)
{
zOrderToTileDictionary.TryAdd(coord.Z, tile);
}
}, cancellationToken);
});
return zOrderToTileDictionary.ToArray();
};
var response = getUpscaleTiles(coordsList.ToArray());
var tilesResponseArray = response.Result;
if (tilesResponseArray.Length == 0)
{
return null;
this._logger.LogDebug($"[{MethodBase.GetCurrentMethod()?.Name}] ended, lastTile: z:{tile.Z}, x:{tile.X}, y:{tile.Y}");
return tile;
}
}
// Get first valid tile that can be upscaled
var orderedTilesArray = tilesResponseArray.OrderBy(kvp => kvp.Key);
Tile? lastTile = orderedTilesArray.Last().Value;
string message = lastTile == null ? "null" : $"z:{lastTile.Z}, x:{lastTile.X}, y:{lastTile.Y}";
this._logger.LogDebug($"[{MethodBase.GetCurrentMethod()?.Name}] ended, lastTile: {message}");
return lastTile;
this._logger.LogDebug($"[{MethodBase.GetCurrentMethod()?.Name}] ended, lastTile: null");
return null;
}

public bool TileExists(Tile tile)
Expand Down
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