From: Steven Rostedt <rostedt@goodmis.org>
To: Tzvetomir Stoyanov <tz.stoyanov@gmail.com>
Cc: Linux Trace Devel <linux-trace-devel@vger.kernel.org>,
Dario Faggioli <dfaggioli@suse.com>
Subject: Re: Clock sync priorities
Date: Thu, 11 Mar 2021 09:53:54 -0500 [thread overview]
Message-ID: <20210311095354.19bfbe1f@gandalf.local.home> (raw)
In-Reply-To: <20210311094401.7c6bf259@gandalf.local.home>
On Thu, 11 Mar 2021 09:44:01 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:
> Dario, feel free to comment on this as well. The host-guest is the
> information stored in each guest file that tells it how its TSC matches the
> host (if -C is not used in the record). The ts2nsecs is done on the host
> where it reads the perf data to find out how the kernels converts the TSC
> to nanoseconds, and this information is stored in each trace.dat file (host
> and guest). This email is about how those will affect the current options
> listed above.
Correction, it's the ts2nsecs that is not done if -C is specified on the
record command line. The host / guest is done if the two can agree on a
protocol.
If -C is not specified, and the host knows exactly how the guest TSC is
set, and it has information (from perf) on how to convert TSC to
nanoseconds, then it will use the TSC clock by default and place the
information needed to convert TSC to nanoseconds in each trace.dat file.
-- Steve
next prev parent reply other threads:[~2021-03-11 14:54 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-11 14:44 Clock sync priorities Steven Rostedt
2021-03-11 14:53 ` Steven Rostedt [this message]
2021-03-11 14:55 ` Tzvetomir Stoyanov
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