Messages in this thread | | | Date | Mon, 16 Oct 2023 11:03:12 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH v1] dynamic_debug: add support for logs destination |
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On Thu, 12 Oct 2023 11:53:52 +0200 Daniel Vetter <daniel@ffwll.ch> wrote:
> > You said that turning the kernel ring buffer contents into strings is a > > very heavy operation, so it is not possible to push this scope > > separation to userspace, right? > > I think it's the kernel that does the formatting, but honestly not sure > how this works with perf traces. Might be that it's actually userspace > doing the formatting later on so that it doesn't incur the overhead while > recording.
perf and trace-cmd do the formatting in user space via libtraceevent:
git://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git
It reads the format files of the events:
/sys/kernel/tracing/events/*/*/format
and uses that to read the raw data saved from the kernel into human readable output.
Note, this means that addresses coming from kernel trace events are not hashed!
-- Steve
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