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Re: Unified tracing buffer
- From: "Martin Bligh" <mbligh at google dot com>
- To: "Masami Hiramatsu" <mhiramat at redhat dot com>
- Cc: "Linux Kernel Mailing List" <linux-kernel at vger dot kernel dot org>, "Linus Torvalds" <torvalds at linux-foundation dot org>, "Thomas Gleixner" <tglx at linutronix dot de>, "Mathieu Desnoyers" <compudj at krystal dot dyndns dot org>, "Steven Rostedt" <rostedt at goodmis dot org>, darren at dvhart dot com, "Frank Ch. Eigler" <fche at redhat dot com>, systemtap-ml <systemtap at sources dot redhat dot com>
- Date: Mon, 22 Sep 2008 17:12:51 -0700
- Subject: Re: Unified tracing buffer
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>> I think we came up with a way to approximate this, using a callback every
>> ms or so as the higher order bits, and a sequential counter in the lower
>> order for those broken platforms.
>
> Sure, that will work.
OK, that'd fix 99% of it, even if we only get time within 1ms or so (but still
good ordering).
>> But perhaps it would be better if we started with a discussion of which
>> platforms can't do global timestamps, and why not? I know some of them
>> are fixable, but perhaps not all.
>
> For example, my laptop (this machine/Core2Duo) doesn't return correct TSC. :-(
Can you define incorrect for me (in this case)?
We had similar problems with some AMD platforms that we can fix by syncing
the TSCs on exit_idle, etc.