Re: [GIT PULL] kdbus for 4.1-rc1

From: Andy Lutomirski
Date: Wed Apr 15 2015 - 18:29:28 EST

On Wed, Apr 15, 2015 at 3:18 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
> On Wed, Apr 15, 2015 at 03:11:17PM -0700, Andy Lutomirski wrote:
>> This is functionally identical to passing AF_UNIX socket fds over
>> SCM_RIGHTS, but I want something much lighter weight.
> Most of the weight in SCM_RIGHTS comes from the fact that you can
> pass AF_UNIX sockets over it, which requires a garbage collector.
> Exclude that and suddenly it becomes very cheap...

I should have been more specific. I don't mean the performance of
SCM_RIGHTS itself; I mean the memory overhead of keeping tons of fds
around, each with their socket data structures and buffers.

I think that dbus could be quite efficiently implemented with a
userspace daemon that just introduces peers to each other, but the fd
explosion could be rather bad for some use cases.

I'll be the first to admit that I don't have a clean API in mind.
There was a lightweight fd proposal way back when, but it never went
anywhere, and it might not be suitable anyway.

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