Re: [Qemu-devel] [PATCH v5] glib: fix g_poll early timeout on windows

[Stefan Hajnoczi]

On Thu, May 08, 2014 at 12:47:10PM +0400, Stanislav Vorobiov wrote:
> From: Sangho Park <address@hidden>
> 
> g_poll has a problem on Windows when using
> timeouts < 10ms, in glib/gpoll.c:
> 
> /* If not, and we have a significant timeout, poll again with
>  * timeout then. Note that this will return indication for only
>  * one event, or only for messages. We ignore timeouts less than
>  * ten milliseconds as they are mostly pointless on Windows, the
>  * MsgWaitForMultipleObjectsEx() call will timeout right away
>  * anyway.
>  */
> if (retval == 0 && (timeout == INFINITE || timeout >= 10))
>   retval = poll_rest (poll_msgs, handles, nhandles, fds, nfds, timeout);
> 
> so whenever g_poll is called with timeout < 10ms it does
> a quick poll instead of wait, this causes significant performance
> degradation of QEMU, thus we should use WaitForMultipleObjectsEx
> directly
> 
> Signed-off-by: Stanislav Vorobiov <address@hidden>
> ---
>  include/glib-compat.h |    9 +++-
>  util/oslib-win32.c    |  112 
> +++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 120 insertions(+), 1 deletion(-)

Thanks, applied to my block tree:
https://github.com/stefanha/qemu/commits/block

Stefan