具有BoundedCapacity的BufferBlock和ActionBlock不使用最大DOP [英] BufferBlock and ActionBlock with BoundedCapacity does not use max DOP
问题描述
我有此代码:
var data = new BufferBlock<int>(new DataflowBlockOptions { BoundedCapacity = 1 });
var action = new ActionBlock<int>(async id =>
{
Console.WriteLine("[{0:T}] #{1}: Start", DateTime.Now, id);
await Task.Delay(1000);
Console.WriteLine("[{0:T}] #{1}: End", DateTime.Now, id);
}, new ExecutionDataflowBlockOptions
{
BoundedCapacity = 1,
MaxDegreeOfParallelism = -1
});
data.LinkTo(action, new DataflowLinkOptions { PropagateCompletion = true });
for (var id = 1; id <= 3; id++)
{
Console.WriteLine("[{0:T}] Sending {1}", DateTime.Now, id);
data.SendAsync(id).Wait();
Console.WriteLine("[{0:T}] Sending {1} complete", DateTime.Now, id);
}
data.Complete();
Task.WhenAll(data.Completion, action.Completion).Wait();
这段代码为我提供了此输出:
And this code gets me this output:
[22:31:22] Sending 1
[22:31:22] Sending 1 complete
[22:31:22] Sending 2
[22:31:22] #1: Start
[22:31:22] Sending 2 complete
[22:31:22] Sending 3
[22:31:23] #1: End
[22:31:23] #2: Start
[22:31:23] Sending 3 complete
[22:31:24] #2: End
[22:31:24] #3: Start
[22:31:25] #3: End
ActionBlock
为什么具有不受限制的DOP不能并行工作?
Why isn't ActionBlock
working in parallel even though it has an unbounded DOP?
推荐答案
您的ActionBlock
似乎具有有限的并行度的原因是因为它的BoundedCapacity
为1.BoundedCapacity
(不同于
The reason your ActionBlock
seems to be have a limited degree of parallelism is because it has a BoundedCapacity
of 1. BoundedCapacity
(unlike InputCount
) includes the item being processed at the moment. This can be easily demonstrated:
var block = new ActionBlock<int>(_ => Task.Delay(-1), new ExecutionDataflowBlockOptions
{
BoundedCapacity = 1,
MaxDegreeOfParallelism = DataflowBlockOptions.Unbounded
});
await block.SendAsync(4); // Adds a new item
await block.SendAsync(4); // Blocks forever
这意味着当您设置MaxDegreeOfParallelism = DataflowBlockOptions.Unbounded
时,该块不能同时接受多个项目,因此实际上限制了您的并行度.
That means that while you set MaxDegreeOfParallelism = DataflowBlockOptions.Unbounded
the block can't accept more than a single item at the time and so practically limiting your degree of parallelism.
您可以通过设置更大的BoundedCapacity
来解决此问题:
You can fix that by setting a larger BoundedCapacity
:
var action = new ActionBlock<int>(async id =>
{
Console.WriteLine("[{0:T}] #{1}: Start", DateTime.Now, id);
await Task.Delay(1000);
Console.WriteLine("[{0:T}] #{1}: End", DateTime.Now, id);
}, new ExecutionDataflowBlockOptions
{
BoundedCapacity = 10,
MaxDegreeOfParallelism = DataflowBlockOptions.Unbounded
});
这篇关于具有BoundedCapacity的BufferBlock和ActionBlock不使用最大DOP的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!