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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 v17 14/18] trace-cmd: Add host trace clock as guest trace argument
Date: Tue, 10 Dec 2019 10:49:43 +0200
Message-ID: <CAPpZLN6xhsdd8Xyocm2rRGesCsW5Wsk2X3ZiEvJW948xXda-kQ@mail.gmail.com> (raw)
In-Reply-To: <20191209143101.146cb619@gandalf.local.home>

On Mon, Dec 9, 2019 at 9:31 PM Steven Rostedt <rostedt@goodmis.org> wrote:
>
[ ... ]
> > diff --git a/tracecmd/trace-record.c b/tracecmd/trace-record.c
> > index 49730d6..e7fb1bd 100644
> > --- a/tracecmd/trace-record.c
> > +++ b/tracecmd/trace-record.c
> > @@ -5405,6 +5405,8 @@ static void parse_record_options(int argc,
> >       char *sav;
> >       int name_counter = 0;
> >       int neg_event = 0;
> > +     struct buffer_instance *instance;
> > +     bool guest_config = false;
>
> Should have a different name, like "clock_set", as "guest_config"
> doesn't let us know what this is about.

I use the same flag in patch 16 from the same series, with the same purpose -
to apply host config to the guest. That's why decided to call it "guest_config".

>
>
> >
> >       init_common_record_context(ctx, curr_cmd);
> >
> > @@ -5562,6 +5564,7 @@ static void parse_record_options(int argc,
> >                       break;
> >               case 'C':
> >                       ctx->instance->ftrace->clock = optarg;
> > +                     guest_config = true;
> >                       break;
> >               case 'v':
> >                       neg_event = 1;
> > @@ -5779,14 +5782,26 @@ static void parse_record_options(int argc,
> >
> >       /* If --date is specified, prepend it to all guest VM flags */
> >       if (ctx->date) {
> > -             struct buffer_instance *instance;
> > -
> >               for_all_instances(instance) {
> >                       if (is_guest(instance))
> >                               add_argv(instance, "--date", true);
> >               }
> >       }
> >
> > +     if (guest_config) {
> > +             /* If -C is specified, prepend clock to all guest VM flags */
> > +             for_all_instances(instance) {
> > +                     if (top_instance.ftrace->clock) {
> > +                             if (is_guest(instance)) {
>
> We should only append this, if the guest didn't have a clock set
> already. As the change log seems to say, if the user states a "-C
> clock" for the guest, that should take precedence over the host clock
> set. That is, a user may specifically state that they are using a
> different clock. If we have frequency and offset set, it should still
> work with different clocks.

The guest config string is not parsed in the host context, that's why the host
doesn't know if a guest has an explicit  "-C clock" argument.
I can parse the guest config here, but this will complicate the implementation.
Using the current approach still guarantees that the user specified
config has higher
priority than injected one - add_argv() API prepends to the beginning
of the string, so
user arguments are always after the injected one. When guest parses
the string, in case of
duplicated "-C clock" arguments, the last one wins.


>
> -- Steve
>
>
> > +                                     add_argv(instance,
> > +                                              (char *)top_instance.ftrace->clock,
> > +                                              true);
> > +                                     add_argv(instance, "-C", true);
> > +                             }
> > +                     }
> > +             }
> > +     }
> > +
> >       if (!ctx->filtered && ctx->instance->filter_mod)
> >               add_func(&ctx->instance->filter_funcs,
> >                        ctx->instance->filter_mod, "*");
>

Thanks !

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

  reply index

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-03 10:35 [PATCH v17 00/18]Timestamp synchronization of host - guest tracing session Tzvetomir Stoyanov (VMware)
2019-12-03 10:35 ` [PATCH v17 01/18] trace-cmd: Implement new lib API: tracecmd_local_events_system() Tzvetomir Stoyanov (VMware)
2019-12-03 10:35 ` [PATCH v17 02/18] trace-cmd: Add support for negative time offsets in trace.dat file Tzvetomir Stoyanov (VMware)
2019-12-03 10:35 ` [PATCH v17 03/18] trace-cmd: Add implementations of htonll() and ntohll() Tzvetomir Stoyanov (VMware)
2019-12-20 13:50   ` Steven Rostedt
2020-01-06 14:30     ` Tzvetomir Stoyanov
2019-12-03 10:35 ` [PATCH v17 04/18] trace-cmd: Add new library APIs for ftrace instances Tzvetomir Stoyanov (VMware)
2019-12-04 16:17   ` Steven Rostedt
2019-12-05 14:40     ` Tzvetomir Stoyanov
2019-12-03 10:35 ` [PATCH v17 05/18] trace-cmd: Add new library API for local CPU count Tzvetomir Stoyanov (VMware)
2019-12-04 20:09   ` Steven Rostedt
2019-12-03 10:35 ` [PATCH v17 06/18] trace-cmd: Add new library API for reading ftrace buffers Tzvetomir Stoyanov (VMware)
2019-12-04 21:10   ` Steven Rostedt
2019-12-03 10:35 ` [PATCH v17 07/18] trace-cmd: Find and store pids of tasks, which run virtual CPUs of given VM Tzvetomir Stoyanov (VMware)
2019-12-04 21:35   ` Steven Rostedt
2019-12-03 10:35 ` [PATCH v17 08/18] trace-cmd: Implement new API tracecmd_add_option_v() Tzvetomir Stoyanov (VMware)
2019-12-04 21:47   ` Steven Rostedt
2019-12-03 10:35 ` [PATCH v17 09/18] trace-cmd: Add new API to generate a unique ID of the tracing session Tzvetomir Stoyanov (VMware)
2019-12-03 10:35 ` [PATCH v17 10/18] trace-cmd: Store the session tracing ID in the trace.dat file Tzvetomir Stoyanov (VMware)
2019-12-03 10:35 ` [PATCH v17 11/18] trace-cmd: Exchange tracing IDs between host and guest Tzvetomir Stoyanov (VMware)
2019-12-04 22:03   ` Steven Rostedt
2019-12-03 10:35 ` [PATCH v17 12/18] trace-cmd: Implement new option in trace.dat file: TRACECMD_OPTION_TIME_SHIFT Tzvetomir Stoyanov (VMware)
2019-12-05  0:46   ` Steven Rostedt
2019-12-05 15:09     ` Tzvetomir Stoyanov
2019-12-03 10:35 ` [PATCH v17 13/18] trace-cmd: Add guest information in host's trace.dat file Tzvetomir Stoyanov (VMware)
2019-12-05  0:59   ` Steven Rostedt
2019-12-03 10:35 ` [PATCH v17 14/18] trace-cmd: Add host trace clock as guest trace argument Tzvetomir Stoyanov (VMware)
2019-12-09 19:31   ` Steven Rostedt
2019-12-10  8:49     ` Tzvetomir Stoyanov [this message]
2019-12-10 15:48       ` Steven Rostedt
2019-12-11  8:21         ` Tzvetomir Stoyanov
2019-12-11 15:01           ` Steven Rostedt
2019-12-03 10:35 ` [PATCH v17 15/18] trace-cmd: Refactor few trace-cmd internal functions Tzvetomir Stoyanov (VMware)
2019-12-09 19:32   ` Steven Rostedt
2019-12-03 10:35 ` [PATCH v17 16/18] trace-cmd: Basic infrastructure for host - guest timestamp synchronization Tzvetomir Stoyanov (VMware)
2019-12-10 17:04   ` Steven Rostedt
2019-12-10 18:39   ` Steven Rostedt
2019-12-12 12:34     ` Tzvetomir Stoyanov
2019-12-12 14:54       ` Steven Rostedt
2019-12-12 14:00     ` Tzvetomir Stoyanov
2019-12-03 10:35 ` [PATCH v17 17/18] trace-cmd: [POC] PTP-like algorithm " Tzvetomir Stoyanov (VMware)
2019-12-03 10:35 ` [PATCH v17 18/18] trace-cmd: Debug scripts for " Tzvetomir Stoyanov (VMware)

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