linux-kernel - Re: Revisit AF_BUS: is it a better way to implement KDBUS?

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Date:	Fri, 31 Jul 2015 17:52:38 +0800
From:	cee1 <fykcee1@...il.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Greg KH <gregkh@...uxfoundation.org>,
	Lennart Poettering <lennart@...ttering.net>,
	David Herrmann <dh.herrmann@...il.com>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
Subject: Re: Revisit AF_BUS: is it a better way to implement KDBUS?

2015-07-31 2:12 GMT+08:00 Andy Lutomirski <luto@...capital.net>:
>
> ISTM kdbus is trying to solve a few problems that really can't be
> solved together: it wants (mostly) reliable delivery, it wants
> globally ordered messages, and it wants broadcasts.  That means that,
> if message N gets broadcast, then, until *every* recipient has
> received message N, message N and all of its successors need to be
> buffered somewhere.  I see how this works (by massive use of tmpfs),
> but I don't see how it's going to work *well*.

For broadcast, what will the kernel behave if:
1. Lots of processes open netlink socket (to receive uevents), but not
consume it. And someone continues to trigger uevents.
2. Lots of processes open inotify to monitor a directory, but not
consume the events. And someone continues to operate files under the
directory.
...

I guess it may have to drop some data if the producer produces too
fast(or the consumers consume too slow). What it needs may be a chance
for recipients to know some broadcast data lost.



-- 
Regards,

- cee1
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