On Thu, Jan 14, 2021 at 12:01 AM Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > > On Thu, 9 Apr 2020 16:28:25 +0300 > "Tzvetomir Stoyanov (VMware)" <tz.stoyanov@xxxxxxxxx> wrote: > > > Add an API to create a tracecmd_handle from a file, > > read and parse only the trace headers from the file. > > This allows to implement opening a trace file on > > stages - reading the trace headers and reading the trace data. > > > > Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@xxxxxxxxx> > > --- > > include/trace-cmd/trace-cmd.h | 1 + > > lib/trace-cmd/trace-input.c | 28 ++++++++++++++++++++++++++++ > > 2 files changed, 29 insertions(+) > > > > diff --git a/include/trace-cmd/trace-cmd.h b/include/trace-cmd/trace-cmd.h > > index 3f96bbde..e22aa251 100644 > > --- a/include/trace-cmd/trace-cmd.h > > +++ b/include/trace-cmd/trace-cmd.h > > @@ -143,6 +143,7 @@ typedef void (*tracecmd_handle_init_func)(struct tracecmd_input *handle, > > struct tracecmd_input *tracecmd_alloc(const char *file); > > struct tracecmd_input *tracecmd_alloc_fd(int fd); > > struct tracecmd_input *tracecmd_open(const char *file); > > +struct tracecmd_input *tracecmd_open_head(const char *file); > > struct tracecmd_input *tracecmd_open_fd(int fd); > > void tracecmd_ref(struct tracecmd_input *handle); > > void tracecmd_close(struct tracecmd_input *handle); > > Hi Tzvetomir, > > I was thinking, before we release libtracecmd, we should add > tracecmd_open() and tracecmd_open_fd() to the library. Just because I find > that tracecmd_open_head() is a awkward name to have alone and only makes > sense if there's already a tracecmd_open(). It will also help with > differentiating the different functions. I'll add tracecmd_open() and tracecmd_open_fd() as APIs. The reason why tracecmd_open_head() is used by KernelShark is that tracecmd_open() reads headers + tracing data and calculates the timestamps. Thus makes it hard to open multiple tracing files from a single trace session and adjust timestamps to be in a same time space. The current KernelShark open flow is: - Open a trace file and parse only the headers with tracecmd_open_head() - Based on the metadata information from the headers, check if there is already an opened file from the same tracing session. If such is found, pair both files with tracecmd_pair_peer(), before reading the tracing data. - Read the tracing data from the file with tracecmd_init_data(). This will adjust timestamps accordingly, if there is a paired peer to the file. We can rename tracecmd_open_head() to something else, or redesign the whole flow of opening trace files > > I know we were going to only have functions that kernelshark uses, but that > may be a little too limiting. > > Thanks! > > -- Steve -- Tzvetomir (Ceco) Stoyanov VMware Open Source Technology Center
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