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From: Gerd Hoffmann <kraxel@redhat.com>
Date: Thu, 21 Jan 2016 11:39:20 +0100
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Subject: Re: [Qemu-devel] RFC: running the user interface in a thread ...
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To: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, David Airlie <airlied@redhat.com>, =?ISO-8859-1?Q?Marc-Andr=E9?= Lureau <mlureau@redhat.com>, qemu-devel <qemu-devel@nongnu.org>

  Hi,

> That sounds good in theory (but see below) since AioContext integrates
> with the glib main loop because it is a GSource.  QEMU code should use
> AioContext where we have high resolution timers and APIs for file
> descriptor, EventNotifier, and BH.

Sounds good.

> Use BH or EventNotifier instead.  BH has optimizations to avoid syscalls
> where possible while EventNotifier is just a plain eventfd/pipe
> (requires a write() syscall for each notification).

How does BH signaling work?  I know I can qemu_bh_schedule from !main
thread to kick BH in main thread context.  The other way around works
using aio_bh_new + aio_bh_call I guess?

thanks,
  Gerd