About performance of D-Bus

[Jerome Philbert]

100ms / 4.7ms = 21 messages only
Moreover, this is the ideal case where the CPU has nothing else to do than
sending messages ...
In the reality, the CPU has lots'of things to do, so I could never send up
to 21 messages.

Jerome

2008/11/4 Thiago Macieira <thiago at kde.org>

> On Tuesday 04 November 2008 11:14:50 Jerome Philbert wrote:
> > For me, the message speed is important and 4.7ms per message is too slow,
> > because :
> >  - 100ms is the max reaction time for the user
> >  - I have several applications interconnected together through an IPC
> (will
> > be DBus or another)
> >  - that can send several messages in the same time
> >
> > In my system, there are situations where several applications send
> several
> > messages in the same time, and it cannot fit the 100ms.
> >
> > That is why I would be interested by a quicker direct DBus.
>
> My desktop system (Intel Core 2 Duo @ 2.33 GHz) can do 3270 calls/sec
> without
> payload, just the roundtrips when both cores are online. That's 0.31 ms per
> round-trip.
>
> With only one core online, the rate drops to 2798 calls/sec.
>
> The system was not idle when I ran those tests. (about 15% of the CPU in
> use)
>
> In any case, if you have more than 100 messages in the space of 100 ms
> (i.e.,
> more than 1000 calls/sec), then there's something wrong with your design.
>
> Yes, the D-Bus library can be profiled and optimised. No one has done that
> since the last major rewrite, apparently because the developers driving the
> development are on the desktop. The embedded developers should take up that
> task if D-Bus isn't fast enough yet.
>
> --
> Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
>  Senior Software Engineer - Nokia, Qt Software
>  Qt Software is hiring - ask me
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