[systemd-devel] sd-bus vs gdbus on dbus-daemon

[Greg KH]

On Wed, Apr 29, 2015 at 04:08:50PM +0200, Umut Tezduyar Lindskog wrote:
> Hi,
> 
> We [1] have noticed that there could be up to %50 performance gain on
> using sd-bus over gdbus on dbus-daemon. For this reason, we have high
> interest in using sd-bus. What are the plans in terms of making sd-bus
> API public?
> 
> Details of the test [2]:
> 
> gdbus.c
>   - g_dbus_proxy_new_for_bus_sync()
>   - 50 x g_dbus_proxy_call_sync()
> 
> sdbus.c
>   - sd_bus_open_system()
>   - 50 x sd_bus_get_property()
> 
> Two applications are run with "ltrace", "perf stat -e cycles", "time"
> and the results are compared.

I'll echo Simon's statement here, making a call to
g_dbus_proxy_call_sync() seems like an odd thing to test.  Is this
really how your application wants to work?  Is it the normal call path
that you need optimized?  How many messages do you normally send, or
want to send, and how big of the data "blob" are you wanting to
transmit/receive here?

I ask as I'm trying to find how people would like to use D-Bus, if the
existing dbus-daemon were sped up in various ways.

Both of these traces show that userspace is sitting around for most of
the time, I don't see a whole lot of actual CPU usage happening, do you?

thanks,

greg k-h