NAME

       tracecmd_get_traceid, tracecmd_get_guest_cpumap - Manage trace session with multiple trace
       peers, recorded in multiple trace files.

SYNOPSIS

       #include <trace-cmd.h>

       unsigned long long tracecmd_get_traceid(struct tracecmd_input *handle);
       int tracecmd_get_guest_cpumap(struct tracecmd_input *handle, unsigned long long trace_id, const char **name, int *vcpu_count, const int **cpu_pid);

DESCRIPTION

       This set of APIs can be used to manage a trace session with multiple trace peers, for
       example, tracing both a host and one or more guest virtual machines. The trace data of
       each peer from the session is recorded in separate trace files. Information about peers
       from the session is stored in the metadata of each trace file. These APIs use that
       information to extract and synchronize the trace data.

       The tracecmd_get_traceid() function returns the trace ID stored in the trace file metadata
       associated with handle. Each peer from a trace session has an ID unique for that peer and
       that trace session only. This ID is used to match multiple trace files recorded in a same
       trace session.

       The tracecmd_get_guest_cpumap() function gets the mapping of guest virtual CPUs (VCPU) to
       the host process that represents those VCPUs and is stored in the metadata of the trace
       file associated with handle. This information is gathered during a host-guest trace
       session and is stored in the host trace file. The trace_id parameter is the trace ID of
       the guest in this particular trace session. If a guest with that ID was part of that
       session, its VCPU to host process mapping is in the host trace file and the information is
       returned in name, vcpu_count and cpu_pid parameters. The name parameter contains the name
       of the guest, the vcpu_count contains the count of VCPUs of that guest and the cpu_pid
       array contains the VCPU to host process mapping. The array is of size vcpu_count where the
       index is VCPU and the value is the process ID (PID) of the host process, running that
       VCPU. The name, vcpu_count and cpu_pid values must not be freed.

RETURN VALUE

       The tracecmd_get_traceid() function returns a 64 bit trace ID.

       The tracecmd_get_guest_cpumap() function returns -1 in case of an error or 0 otherwise. If
       0 is returned, then the name, vcpu_count and cpu_pid parameters contain the requested
       information.

EXAMPLE

           #include <trace-cmd.h>
           ...
           struct tracecmd_input *host = tracecmd_open("trace.dat");
                   if (!host) {
                           /* Failed to open host trace file */
                   }

           struct tracecmd_input *guest1 = tracecmd_open_head("trace-Guest1.dat");
                   if (!guest1) {
                           /* Failed to open guest1 trace file */
                   }
           struct tracecmd_input *guest2 = tracecmd_open_head("trace-Guest2.dat");
                   if (!guest2) {
                           /* Failed to open guest2 trace file */
                   }

           unsigned long long guest_id_1 = tracecmd_get_traceid(guest1);
           unsigned long long guest_id_2 = tracecmd_get_traceid(guest2);
           int *cpu_pid_1, *cpu_pid_2;
           int vcount_1, vcount_2;
           char *name_1, *name_2;

                   if (!tracecmd_get_guest_cpumap(host, guest_id_1, &name_1, &vcount_1, &cpu_pid_1)) {
                           /* The Host and a guest1 with name_1 are part of the same trace session.
                            * Got guest1 VCPU to host PID mapping.
                            */
                   }
                   if (!tracecmd_get_guest_cpumap(host, guest_id_2, &name_2, &vcount_2, &cpu_pid_2)) {
                           /* The Host and a guest2 with name_2 are part of the same trace session.
                            * Got guest2 VCPU to host PID mapping.
                            */
                   }
           ...
                   tracecmd_close(guest1);
                   tracecmd_close(guest2);
                   tracecmd_close(handle);

FILES

           trace-cmd.h
                   Header file to include in order to have access to the library APIs.
           -ltracecmd
                   Linker switch to add when building a program that uses the library.

SEE ALSO

       libtracefs(3), libtraceevent(3), trace-cmd(1) trace-cmd.dat(5)

AUTHOR

           Steven Rostedt <rostedt@goodmis.org[1]>
           Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>

REPORTING BUGS

       Report bugs to <linux-trace-devel@vger.kernel.org[3]>

LICENSE

       libtracecmd is Free Software licensed under the GNU LGPL 2.1

RESOURCES

       https://git.kernel.org/pub/scm/utils/trace-cmd/trace-cmd.git/

COPYING

       Copyright (C) 2020 VMware, Inc. Free use of this software is granted under the terms of
       the GNU Public License (GPL).

NOTES

        1. rostedt@goodmis.org
           mailto:rostedt@goodmis.org

        2. tz.stoyanov@gmail.com
           mailto:tz.stoyanov@gmail.com

        3. linux-trace-devel@vger.kernel.org
           mailto:linux-trace-devel@vger.kernel.org