linux-kernel - Re: [PATCH v4 01/24] ring-buffer: Introduce ring-buffer remotes

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Message-ID: <aBx1EBa6QFH7dmqs@google.com>
Date: Thu, 8 May 2025 10:10:40 +0100
From: Vincent Donnefort <vdonnefort@...gle.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: mhiramat@...nel.org, mathieu.desnoyers@...icios.com,
	linux-trace-kernel@...r.kernel.org, maz@...nel.org,
	oliver.upton@...ux.dev, joey.gouly@....com, suzuki.poulose@....com,
	yuzenghui@...wei.com, kvmarm@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org, jstultz@...gle.com,
	qperret@...gle.com, will@...nel.org, kernel-team@...roid.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 01/24] ring-buffer: Introduce ring-buffer remotes

On Wed, May 07, 2025 at 07:47:22PM -0400, Steven Rostedt wrote:
> On Tue,  6 May 2025 17:47:57 +0100
> Vincent Donnefort <vdonnefort@...gle.com> wrote:
> 
> 
> > diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
> > index 56e27263acf8..c0c7f8a0dcb3 100644
> > --- a/include/linux/ring_buffer.h
> > +++ b/include/linux/ring_buffer.h
> > @@ -248,4 +248,67 @@ int ring_buffer_map(struct trace_buffer *buffer, int cpu,
> >  		    struct vm_area_struct *vma);
> >  int ring_buffer_unmap(struct trace_buffer *buffer, int cpu);
> >  int ring_buffer_map_get_reader(struct trace_buffer *buffer, int cpu);
> > +
> > +#define meta_pages_lost(__meta) \
> > +	((__meta)->Reserved1)
> > +#define meta_pages_touched(__meta) \
> > +	((__meta)->Reserved2)
> 
> Hmm, I wonder if this would be worth adding to the user interface?

Would trace-cmd have any use for those fields? That said, even if it does not at
the moment, it would mean the meta-page has a single version between
kern/user-space and hyp/kern which is probably better?

I can add an additional patch in this series to extend the meta-page.

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