ASP.NET Core 6调用WCF服务时内存占用过高问题求助

背景 #

我有一个ASP.NET Core 6应用，会定时调用WCF服务获取数据，核心依赖注入配置如下：

builder.Services.AddSingleton<StorageCostDataService>();
builder.Services.AddSingleton<PeriodicDataSnapshotService>();
builder.Services.AddHostedService<PeriodicDataSnapshotService>(provider => 
provider.GetRequiredService<PeriodicDataSnapshotService>());

其中StorageCostDataService是WCF客户端，负责从服务端获取数据；PeriodicDataSnapshotService作为后台服务定时执行逻辑，定义如下：

public class PeriodicDataSnapshotService : BackgroundService
{
    private PeriodicTimer? _periodicTimer;

    private readonly StorageCostDataService _storageCostDataService;

    public PeriodicDataSnapshotService(StorageCostDataService storageCostDataService)
    {
        _storageCostDataService = storageCostDataService;
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        _periodicTimer = new PeriodicTimer(_period);

        while (await _periodicTimer.WaitForNextTickAsync(stoppingToken))
        {
            try
            {
                using var storageStateViewerContext = new StorageStateViewerContext();

                var storageCostOverviewData = _storageCostDataService.GetStorageCostOverviewData(2000);

                var storageCostOverviewRemainingValueHistoryData = _storageCostDataService.GetStorageCostOverviewRemainingValueData(2000);

                storageStateViewerContext.StorageOverviewHistories.Add(storageOverviewHistory);
                storageStateViewerContext.SaveChanges();

                storageCostOverviewData = null;
                storageCostOverviewRemainingValueHistoryData = null;
            }
            catch (Exception ex)
            {
                _logger.LogError(ex.Message);
            }
        }

        throw new NotImplementedException();
    }
}

该服务从WCF获取数据后处理并存储到EF Core的DbContext中。调试时发现内存占用异常：启动初始约60MB，首次调用服务后增至260MB，之后每次定时执行都会新增200MB内存；GC触发后仅从3GB左右降至2GB，无法完全回收。内存快照显示，大量未被回收的死对象均来自StorageCostDataService。

WCF客户端核心实现如下：

public Dictionary<string, List<ErpBatchCostOverviewItem>> GetStorageCostOverviewData(int limit)
{
    using (var svc = new ErpInterfaceWebserviceClient())
    {
        var b = svc.Endpoint.Binding as BasicHttpBinding;

        if (b == null)
        {
            throw new Exception("Couldn't create service endpoint");
        }

        b.MaxReceivedMessageSize = int.MaxValue;
        b.BypassProxyOnLocal = true;
        b.UseDefaultWebProxy = false;

        var endpoint = svc.Endpoint;
        endpoint.Address = new EndpointAddress("http://svr-el-sql.work.local:1035/ErpInterface");

        svc.OpenAsync().Wait();

        var serverData = svc.GetErpBatchCostOverview();

        svc.Close();

        var erpBatchCostOverviewItems = serverData
                .Where(d => d.GroupId != 71)
                .GroupBy(d => d.Ident)
                .OrderByDescending(d => d.Sum(e => e.Price * e.Amount))
                .Take(limit)
                .ToDictionary(d => d.Key, d => d.ToList())
            ;

        return erpBatchCostOverviewItems;
    }
}

已按建议将DbContext包裹在using语句中，调整PeriodicTimer为局部字段，但内存问题未改善。Visual Studio诊断工具显示，GC分别在400MB、1.5GB、2.2GB时触发，回收后仍残留大量ErpInterfaceService相关对象。

疑问 #

为何这些WCF相关对象无法被GC完全回收？

内容的提问来源于stack exchange，提问作者Tom L.