Re: [PATCH] kernel-shark-2.alpha: Use new tracecmd API to open guest tracing file

["Yordan Karadzhov (VMware)" <y.karadz@xxxxxxxxx>]

On 3.04.20 г. 15:26 ч., Tzvetomir Stoyanov wrote:
> On Fri, Apr 3, 2020 at 2:39 PM Yordan Karadzhov (VMware)
> <y.karadz@xxxxxxxxx> wrote:
> > On 1.04.20 г. 19:45 ч., Tzvetomir Stoyanov (VMware) wrote:
> > > From: Tzvetomir (VMware)  Stoyanov <tz.stoyanov@xxxxxxxxx>
> > >
> > > The new tracecmd API tracecmd_open_merge() is used to open guest
> > > tracing file and synchronize it to the host file.
> > > This change is for testing purposes only, to test the new per CPU
> > > timestamps synchronization logic.
> > > It assumes that the stream with id 0 is the host one, and all others are
> > > guest streams.
> > > This change depends on commit:
> > >    "trace-cmd: Add new API to merge two trace files"
> > > where the new tracecmd API is introduced.
> > >
> > > Signed-off-by: Tzvetomir (VMware)  Stoyanov <tz.stoyanov@xxxxxxxxx>
> > > ---
> > >    src/libkshark-tepdata.c | 13 +++++++++++--
> > >    1 file changed, 11 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/src/libkshark-tepdata.c b/src/libkshark-tepdata.c
> > > index 8678e12..b80b945 100644
> > > --- a/src/libkshark-tepdata.c
> > > +++ b/src/libkshark-tepdata.c
> > > @@ -1008,8 +1008,17 @@ int kshark_tep_init_input(struct kshark_data_stream *stream,
> > >        tep_handle = calloc(1, sizeof(*tep_handle));
> > >        if (!tep_handle)
> > >                return -EFAULT;
> > > -
> > > -     tep_handle->input = tracecmd_open(file);
> >
> > Hi Ceco,
> >
> > Is it possible to avoid the hard-coded ID number of the primary stream
> > (zero in this case)?
>
> Yes, the first version of the patch is more a POC, to test the new
> tracecmd_open_merge() API.
>
> > Maybe we can add data field to "struct tepdata_handle" that can be used
> > to indicate if the stream is "primary" or not. Note that "struct
> > tepdata_handle" is defined only for "libkshark-tepdata.c".
>
> I think a new "unsigned int flags" member should be added to
> struct kshark_data_stream;
> and flags should indicate if the stream is primary or not, depending
> on the way the file is loaded:
>   using "-i" option, or "File -> Open" from the menu - primary
>   using "-a" option, or "File -> Append" from the menu - secondary

Maybe it has to be a bit more sophisticated. Does the "primary" stream 
know how to recognize its "secondary" streams?


> > Also do we consider a case when we will need to load more than one
> > "primary" stream?
>
> In the host - guest tracing, there is no use case with more than one
> primary stream,
> but may be there could be other use cases where more than one primary
> stream will
> be needed ?
>
> Is it possible to append more than one secondary files, using the
> current KernelShark 2 ?
> I tried appending two files, specifying "-a" option twice, but only
> the first "-a" file was appended.
Yes, this can be done from the menus, but you are right that something 
goes wrong when trying to do this from the command line. I will 
investigate and will try to get it fixed.

Thanks!
Yordan

> > Thanks!
> > Yordan
> >
> >
> > > +     if (stream->stream_id > 0) {
> > > +             struct kshark_data_stream *primary;
> > > +
> > > +             primary = kshark_get_data_stream(kshark_ctx, 0);
> > > +             if (primary && primary->file)
> > > +                     tep_handle->input = tracecmd_open_merge(file,
> > > +                                                             primary->file);
> > > +             else
> > > +                     tep_handle->input = tracecmd_open(file);
> > > +     } else
> > > +             tep_handle->input = tracecmd_open(file);
> > >        if (!tep_handle->input) {
> > >                free(tep_handle);
> > >                stream->interface.handle = NULL;