LIBTRACECMD(3) libtracefs Manual LIBTRACECMD(3)
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
libtracefs 04/08/2024 LIBTRACECMD(3)
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