gRPC core: why polling_island has a field "merged_to"

[Wankai Zhang]

Hello, all:

I am using c/c++.

I am confused of polling_island data structure. Why it contains a field "merged_to" ? 

Could anyone help me?

[Sree Kuchibhotla]

Hi Wankai,

The following design document explains the rationale behind the new epoll implementation. Polling island was added as a part of this change.

https://github.com/grpc/grpc/blob/master/doc/epoll-polling-engine.md

(see section 4).

Here is some high level summary:

- Polling island represents the underlying epoll set containing the file descriptors (which is why it contains the epoll-fd)

- The main idea in having them is to prevent a file descriptor from being in multiple epoll sets. This means that whenever we add a file descriptor (that already belongs to an epoll set) to another epoll set,  we merge the underlying polling islands and old polling island's merged_to field points to the new polling island..

the document's section 4 explains it all

thanks,

Sree

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[Wankai Zhang]

Thanks, @Sree, it's very helpful.

在 2016年10月19日星期三 UTC+8上午5:50:01，Sree Kuchibhotla写道：

Hi Wankai,

The following design document explains the rationale behind the new epoll implementation. Polling island was added as a part of this change.

https://github.com/grpc/grpc/blob/master/doc/epoll-polling-engine.md

(see section 4).

Here is some high level summary:

- Polling island represents the underlying epoll set containing the file descriptors (which is why it contains the epoll-fd)

- The main idea in having them is to prevent a file descriptor from being in multiple epoll sets. This means that whenever we add a file descriptor (that already belongs to an epoll set) to another epoll set,  we merge the underlying polling islands and old polling island's merged_to field points to the new polling island..

the document's section 4 explains it all

thanks,

Sree

On Tue, Oct 18, 2016 at 8:38 AM, Wankai Zhang <wankai...@gmail.com> wrote:

Hello, all:

I am using c/c++.

I am confused of polling_island data structure. Why it contains a field "merged_to" ? 

Could anyone help me?

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