[Qemu-devel] 100% host cpu with gtk3

[Qemu-devel] 100% host cpu with gtk3

[Fam Zheng]

Hi Gerd,

When using the gtk frontend, it seems there is a busy loop in libgtk repeatedly
calling recvmsg, causing 100% cpu on the main thread. This started to appear
after I upgraded to Fedora 28. Is this a known problem?

Any hints on how to track it down?

Fam

Re: [Qemu-devel] 100% host cpu with gtk3

[Gerd Hoffmann]

On Wed, Jun 06, 2018 at 06:43:57PM +0800, Fam Zheng wrote:
> Hi Gerd,
> 
> When using the gtk frontend, it seems there is a busy loop in libgtk repeatedly
> calling recvmsg, causing 100% cpu on the main thread. This started to appear
> after I upgraded to Fedora 28. Is this a known problem?

No, didn't saw this (but running rhel-7 on my workstation).

> Any hints on how to track it down?

perf top, maybe with with call graphs would be the first thing I
would try ...

cheers,
  Gerd

Re: [Qemu-devel] 100% host cpu with gtk3

[Daniel P. Berrangé]

On Wed, Jun 06, 2018 at 06:43:57PM +0800, Fam Zheng wrote:
> Hi Gerd,
> 
> When using the gtk frontend, it seems there is a busy loop in libgtk repeatedly
> calling recvmsg, causing 100% cpu on the main thread. This started to appear
> after I upgraded to Fedora 28. Is this a known problem?
> 
> Any hints on how to track it down?

GLib has systemtap probes registered in its dispatch code. These probes
will include the name of the GSource. You could possibly use this to
identify which GSource is firing too often.

eg in gmain.c in glib code there are these events to hook into:

          TRACE (GLIB_MAIN_BEFORE_DISPATCH (g_source_get_name (source), source,
                                            dispatch, callback, user_data));
          need_destroy = !(* dispatch) (source, callback, user_data);
          TRACE (GLIB_MAIN_AFTER_DISPATCH (g_source_get_name (source), source,
                                           dispatch, need_destroy));



Regards,
Daniel
-- 
|: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org         -o-            https://fstop138.berrange.com :|
|: https://entangle-photo.org    -o-    https://www.instagram.com/dberrange :|