Off-topic: D-Bus in the kernel
alban.crequy at collabora.co.uk
Fri Sep 17 09:00:16 PDT 2010
Le Fri, 17 Sep 2010 11:47:28 -0400,
Havoc Pennington <hp at pobox.com> a écrit :
> On Fri, Sep 17, 2010 at 11:37 AM, Alban Crequy
> <alban.crequy at collabora.co.uk> wrote:
> > No. It does the minimum parsing required to route the messages
> > (header fields 'sender', 'destination', 'interface', etc.). There
> > is no validation, except a few incomplete ones in the headers of
> > the message.
> OK. You have to set the sender header, for example, to be correct with
> daemon semantics. (This is what I mean about the test suite.)
Yes, it sets the 'sender' header correctly when dbus-daemon is bypassed.
But it is not set when the message is delivered to dbus-daemon (for
D-Bus activation, for the bus driver, or other cases).
> >> How much of the perf gain is due to different
> >> behavior/semantics vs. avoiding the context switch and copies?
> > I don't know, I need to test that. Is there an easy way to disable
> > validation in dbus-daemon?
> Yeah, there is a pretty easy code hack. in
> dbus-message.c:load_message() change the validation mode set at the
> This still won't disable header _parsing_ though which is itself a lot
> slower than it should be in libdbus. The only performance thing
> libdbus really gets right is that it avoids a lot of gratuitous
> copying of the message.
Thanks for the pointer.
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