如何确定.NET中的并发HTTP请求瓶颈？

我正在尝试尽可能快地向URL发出尽可能多的HTTP请求.

我正在使用这段代码来限制最大的并行度,所以我不会通过Tasks一次性产生大量的内容来溢出内存.

    public static Task ForEachAsync(this IEnumerable source, int dop, Func body)
    {
        return Task.WhenAll(
            from partition in Partitioner.Create(source).GetPartitions(dop)
            select Task.Run(async delegate {
                using (partition)
                    while (partition.MoveNext())
                        await body(partition.Current);
            }));
    }

这似乎工作正常.

body() 基本归结为:

async Task Body()
{
    var r = WebRequest.Create("// the url");
    await r.GetResponseAsync();
}

但是,我似乎在某个地方遇到了瓶颈.如果我尝试进行2500迭代,使用不同的值,dop我会得到以下结果:

DOP: 50
Total Time: 00:00:14.4801781
Average (ms): 246.6088
StDev: 84.1327983759009

DOP: 75
Total Time: 00:00:09.8089530
Average (ms): 265.758
StDev: 110.22912244956

DOP: 100
Total Time: 00:00:11.9899793
Average (ms): 344.9168
StDev: 173.281468939295

DOP: 200
Total Time: 00:00:09.1512825
Average (ms): 627.0492
StDev: 572.616238312676

DOP: 500
Total Time: 00:00:09.3556978
Average (ms): 1361.5328
StDev: 1798.70589239157

DOP: 750
Total Time: 00:00:12.6076035
Average (ms): 2009.058
Normal Total: 5022646
StDev: 2348.20874093199


DOP: 1000
Total Time: 00:00:11.4721195
Average (ms): 2453.782
StDev: 2481.56238190299

DOP: 2000
Total: 00:00:11.6039888
Average (ms): 4100.5536
StDev: 2459.36983911063

这似乎暗示dop=50不到瓶颈.dop~=100然而,当你达到上面时,你会注意到Average每个请求所花费的时间(Func body即运行2500时间的平均值)几乎呈线性增加DOP(这些结果中的噪声确实存在,但它们可以重复,但误差很小).

这表明工作中有一个"队列" body正在做,对吧？

我已经开始了

ServicePointManager.DefaultConnectionLimit = int.MaxValue;

如果我这样做

servicePoint = ServicePointManager.FindServicePoint("// the url", null);

和监视器

servicePoint.CurrentConnections 

在每次执行时body,它总是等于dop(除了初始加速和尾部关闭).

我从各种网络尝试过这个,所以它不太可能是基于硬件的,它不应该是远程服务器,因为它设计用于大量入站负载(不是我所说的数字甚至很重)

我怎样才能更好地描述我在做什么？