Re: [PATCH RFC 0/5] rust: implement tracing

["Daniel P. Berrangé" <berrange@redhat.com>]

On Tue, Aug 05, 2025 at 07:25:39PM +0300, Manos Pitsidianakis wrote:
> On Tue, Aug 5, 2025 at 7:05 PM Daniel P. Berrangé <berrange@redhat.com> wrote:
> >
> > On Mon, Aug 04, 2025 at 04:47:13PM +0300, Manos Pitsidianakis wrote:
> > > This RFC series contains some simple patches I've been sitting on for
> > > some months to allow tracing in rust devices in a similar matter to C,
> > > only it's done via a proc-macro codegen instead of using tracetool
> > > script or equivalent.
> >
> > IIUC, this series is only emitting the traces events via the
> > qemu_log function, and so feels like it is missing the benefit
> > of tracing, vs the traditional logging framework.
> >
> > In our RHEL & Fedora distro builds we disable the log backend
> > and enable dtrace, so that we have fully dynamic tracing and
> > observability across the kernel, qemu, libvirt and other
> > components with dtrace integration.
> 
> Hi Daniel,
> 
> Thanks for the insight! Do you have any points where I should look at
> the trace implementation for how the different backends are supported?
> 
> So I think there's already work in progress to support proper tracing
> for Rust, I only sent this as a temporary fixup to provide some kind
> of parity between C and Rust implementations until a proper, better
> solution is available that can replace it.

Can the rust code not easily consume the existing functions in the
trace.h files generated for the C code as a short-term solution ?

It would not benefit from the code inlining in the same way as C
would, but it would at least give feature parity for tracing with
all the trace backends are available.

Then, we can look at optimizing with a pure rust impl of some
backends at a later date, to regain what we lost from lack of
inlining ?

With regards,
Daniel
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