Re: [PATCH 1/1] eventfd: implementation of EFD_MASK flag

Martin Sustrik [off-list ref] wrote:

On 09/02/13 04:54, Eric Wong wrote:

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Using one eventfd per userspace socket still seems a bit wasteful.

Wasteful in what sense? Occupying a slot in file descriptor table?
That's the price for having the socket uniquely identified by the
fd.

Yes.  I realize eventfd is small, but I don't think eventfd is needed
at all, here.  Just one pipe.

Ah. Got you! You mean not to change the kernel, just use pipe for
the purpose.

However, the convoluted pipe-style design is the problem I am trying
to solve rather than the solution. It leads to convoluted APIs with
convoluted semantics as described in the article. I've been using
that kind of design for past 8 years and every time I have to deal
with it I swear that one day I will implement a proper in-kernel
solution to get rid of the hack.

And now I have finally done so.

Yes, your eventfd change is probably the best way if you want/need
to only watch a subset of your sockets, especially if you want
poll/select to be an option.