'\" t
.\" Title: libtracecmd
.\" Author: [see the "AUTHOR" section]
.\" Generator: DocBook XSL Stylesheets vsnapshot
.\" Date: 04/07/2024
.\" Manual: libtracefs Manual
.\" Source: libtracefs
.\" Language: English
.\"
.TH "LIBTRACECMD" "3" "04/07/2024" "libtracefs" "libtracefs Manual"
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.SH "NAME"
tracecmd_get_traceid, tracecmd_get_guest_cpumap \- Manage trace session with multiple trace peers, recorded in multiple trace files\&.
.SH "SYNOPSIS"
.sp
.nf
\fB#include \fR
unsigned long long \fBtracecmd_get_traceid\fR(struct tracecmd_input *\fIhandle\fR);
int \fBtracecmd_get_guest_cpumap\fR(struct tracecmd_input *\fIhandle\fR, unsigned long long \fItrace_id\fR, const char **\fIname\fR, int *\fIvcpu_count\fR, const int **\fIcpu_pid\fR);
.fi
.SH "DESCRIPTION"
.sp
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\&.
.sp
The \fBtracecmd_get_traceid()\fR function returns the trace ID stored in the trace file metadata associated with \fIhandle\fR\&. 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\&.
.sp
The \fBtracecmd_get_guest_cpumap()\fR 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 \fIhandle\fR\&. This information is gathered during a host\-guest trace session and is stored in the host trace file\&. The \fItrace_id\fR 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 \fIname\fR, \fIvcpu_count\fR and \fIcpu_pid\fR parameters\&. The \fIname\fR parameter contains the name of the guest, the \fIvcpu_count\fR contains the count of VCPUs of that guest and the \fIcpu_pid\fR array contains the VCPU to host process mapping\&. The array is of size \fIvcpu_count\fR where the index is VCPU and the value is the process ID (PID) of the host process, running that VCPU\&. The \fIname\fR, \fIvcpu_count\fR and \fIcpu_pid\fR values must \fBnot\fR be freed\&.
.SH "RETURN VALUE"
.sp
The \fBtracecmd_get_traceid()\fR function returns a 64 bit trace ID\&.
.sp
The \fBtracecmd_get_guest_cpumap()\fR function returns \-1 in case of an error or 0 otherwise\&. If 0 is returned, then the \fIname\fR, \fIvcpu_count\fR and \fIcpu_pid\fR parameters contain the requested information\&.
.SH "EXAMPLE"
.sp
.if n \{\
.RS 4
.\}
.nf
#include
\&.\&.\&.
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);
.fi
.if n \{\
.RE
.\}
.SH "FILES"
.sp
.if n \{\
.RS 4
.\}
.nf
\fBtrace\-cmd\&.h\fR
Header file to include in order to have access to the library APIs\&.
\fB\-ltracecmd\fR
Linker switch to add when building a program that uses the library\&.
.fi
.if n \{\
.RE
.\}
.SH "SEE ALSO"
.sp
\fBlibtracefs(3)\fR, \fBlibtraceevent(3)\fR, \fBtrace\-cmd(1)\fR \fBtrace\-cmd\&.dat(5)\fR
.SH "AUTHOR"
.sp
.if n \{\
.RS 4
.\}
.nf
\fBSteven Rostedt\fR <\m[blue]\fBrostedt@goodmis\&.org\fR\m[]\&\s-2\u[1]\d\s+2>
\fBTzvetomir Stoyanov\fR <\m[blue]\fBtz\&.stoyanov@gmail\&.com\fR\m[]\&\s-2\u[2]\d\s+2>
.fi
.if n \{\
.RE
.\}
.SH "REPORTING BUGS"
.sp
Report bugs to <\m[blue]\fBlinux\-trace\-devel@vger\&.kernel\&.org\fR\m[]\&\s-2\u[3]\d\s+2>
.SH "LICENSE"
.sp
libtracecmd is Free Software licensed under the GNU LGPL 2\&.1
.SH "RESOURCES"
.sp
\m[blue]\fBhttps://git\&.kernel\&.org/pub/scm/utils/trace\-cmd/trace\-cmd\&.git/\fR\m[]
.SH "COPYING"
.sp
Copyright (C) 2020 VMware, Inc\&. Free use of this software is granted under the terms of the GNU Public License (GPL)\&.
.SH "NOTES"
.IP " 1." 4
rostedt@goodmis.org
.RS 4
\%mailto:rostedt@goodmis.org
.RE
.IP " 2." 4
tz.stoyanov@gmail.com
.RS 4
\%mailto:tz.stoyanov@gmail.com
.RE
.IP " 3." 4
linux-trace-devel@vger.kernel.org
.RS 4
\%mailto:linux-trace-devel@vger.kernel.org
.RE