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From: Tzvetomir Stoyanov <tz.stoyanov@gmail.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-trace-devel@vger.kernel.org
Subject: Re: [PATCH v18 13/18] trace-cmd: Add guest information in host's trace.dat file
Date: Mon, 6 Jan 2020 16:43:03 +0200
Message-ID: <CAPpZLN5HaooBR4i=gb874eyTVBjdtwT2e=3G7+1gBv1yqiBOPw@mail.gmail.com> (raw)
In-Reply-To: <20191220155221.6face370@gandalf.local.home>

On Fri, Dec 20, 2019 at 10:52 PM Steven Rostedt <rostedt@goodmis.org> wrote:
>
> On Fri, 13 Dec 2019 17:30:24 +0200
> "Tzvetomir Stoyanov (VMware)" <tz.stoyanov@gmail.com> wrote:
>
> > New trace.dat option is introduced: TRACECMD_OPTION_GUEST.
> > Written in the host's trace.dat file, it contains information about
> > guests, traced at the same time: guest trace ID, number of VCPUs and
> > PIDs of the host tasks, running those VCPU. The data is stored in
> > the file as NULL terminated string:
> >       "Guest %s %llu %d\n" -> guest name, number of VCPUs
> >       "%d %d\n" -> VCPU, PID of host task
> >       .....
> >       "%d %d\n" -> VCPU, PID of host task
>
> Why is this a string, and not a structure?

To avoid endian long long conversions, and to simplify reading of
trace.dat file, for debug purposes.
I would suggest to keep it text, for two reasons:
 - this information is not huge, the binary format will not reduce the
size of the trace.dat file significantly.
 - it is very useful to be possible to check what guest information is
stored in the file, using simple cat

We could think of implementing some stand alone trace.dat file reader,
to extract and display that meta data information.

>
> -- Steve



-- 
Tzvetomir (Ceco) Stoyanov
VMware Open Source Technology Center

  reply index

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-13 15:30 [PATCH v18 00/18]Timestamp synchronization of host - guest tracing session Tzvetomir Stoyanov (VMware)
2019-12-13 15:30 ` [PATCH v18 01/18] trace-cmd: Implement new lib API: tracecmd_local_events_system() Tzvetomir Stoyanov (VMware)
2019-12-13 15:30 ` [PATCH v18 02/18] trace-cmd: Add support for negative time offsets in trace.dat file Tzvetomir Stoyanov (VMware)
2019-12-13 15:30 ` [PATCH v18 03/18] trace-cmd: Add implementations of htonll() and ntohll() Tzvetomir Stoyanov (VMware)
2019-12-21  2:34   ` Steven Rostedt
2019-12-13 15:30 ` [PATCH v18 04/18] trace-cmd: Add new library APIs for ftrace instances Tzvetomir Stoyanov (VMware)
2019-12-21  3:03   ` Steven Rostedt
2020-01-06 14:47     ` Tzvetomir Stoyanov
2019-12-13 15:30 ` [PATCH v18 05/18] trace-cmd: Add new library API for local CPU count Tzvetomir Stoyanov (VMware)
2019-12-13 15:30 ` [PATCH v18 06/18] trace-cmd: Add new library API for reading ftrace buffers Tzvetomir Stoyanov (VMware)
2019-12-13 15:30 ` [PATCH v18 07/18] trace-cmd: Find and store pids of tasks, which run virtual CPUs of given VM Tzvetomir Stoyanov (VMware)
2019-12-13 15:30 ` [PATCH v18 08/18] trace-cmd: Implement new API tracecmd_add_option_v() Tzvetomir Stoyanov (VMware)
2019-12-13 15:30 ` [PATCH v18 09/18] trace-cmd: Add new API to generate a unique ID of the tracing session Tzvetomir Stoyanov (VMware)
2019-12-13 15:30 ` [PATCH v18 10/18] trace-cmd: Store the session tracing ID in the trace.dat file Tzvetomir Stoyanov (VMware)
2019-12-20 20:04   ` Steven Rostedt
2020-01-06 14:33     ` Tzvetomir Stoyanov
2019-12-13 15:30 ` [PATCH v18 11/18] trace-cmd: Exchange tracing IDs between host and guest Tzvetomir Stoyanov (VMware)
2019-12-13 15:30 ` [PATCH v18 12/18] trace-cmd: Implement new option in trace.dat file: TRACECMD_OPTION_TIME_SHIFT Tzvetomir Stoyanov (VMware)
2019-12-21  3:19   ` Steven Rostedt
2019-12-13 15:30 ` [PATCH v18 13/18] trace-cmd: Add guest information in host's trace.dat file Tzvetomir Stoyanov (VMware)
2019-12-20 20:52   ` Steven Rostedt
2020-01-06 14:43     ` Tzvetomir Stoyanov [this message]
2020-01-06 14:55       ` Steven Rostedt
2019-12-13 15:30 ` [PATCH v18 14/18] trace-cmd: Add host trace clock as guest trace argument Tzvetomir Stoyanov (VMware)
2019-12-13 15:30 ` [PATCH v18 15/18] trace-cmd: Refactor few trace-cmd internal functions Tzvetomir Stoyanov (VMware)
2019-12-13 15:30 ` [PATCH v18 16/18] trace-cmd: Basic infrastructure for host - guest timestamp synchronization Tzvetomir Stoyanov (VMware)
2019-12-21  4:48   ` Steven Rostedt
2020-01-31  9:53     ` Tzvetomir Stoyanov
2020-01-31 14:49       ` Steven Rostedt
2019-12-13 15:30 ` [PATCH v18 17/18] trace-cmd: [POC] PTP-like algorithm " Tzvetomir Stoyanov (VMware)
2019-12-13 15:30 ` [PATCH v18 18/18] trace-cmd: Debug scripts for " Tzvetomir Stoyanov (VMware)

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