1LIBTRACECMD(3) libtracefs Manual LIBTRACECMD(3)
2
6 tracecmd_get_traceid, tracecmd_get_guest_cpumap - Manage trace session
7 with multiple trace peers, recorded in multiple trace files.
8
10 #include <trace-cmd.h>
11 unsigned long long tracecmd_get_traceid(struct tracecmd_input *handle);
13 int tracecmd_get_guest_cpumap(struct tracecmd_input *handle, unsigned long long trace_id, const char **name, int *vcpu_count, const int **cpu_pid);
14
16 This set of APIs can be used to manage a trace session with multiple
17 trace peers, for example, tracing both a host and one or more guest
18 virtual machines. The trace data of each peer from the session is
19 recorded in separate trace files. Information about peers from the
20 session is stored in the metadata of each trace file. These APIs use
21 that information to extract and synchronize the trace data.
22 The tracecmd_get_traceid() function returns the trace ID stored in the
24 trace file metadata associated with handle. Each peer from a trace
25 session has an ID unique for that peer and that trace session only.
26 This ID is used to match multiple trace files recorded in a same trace
27 session.
28 The tracecmd_get_guest_cpumap() function gets the mapping of guest
30 virtual CPUs (VCPU) to the host process that represents those VCPUs and
31 is stored in the metadata of the trace file associated with handle.
32 This information is gathered during a host-guest trace session and is
33 stored in the host trace file. The trace_id parameter is the trace ID
34 of the guest in this particular trace session. If a guest with that ID
35 was part of that session, its VCPU to host process mapping is in the
36 host trace file and the information is returned in name, vcpu_count and
37 cpu_pid parameters. The name parameter contains the name of the guest,
38 the vcpu_count contains the count of VCPUs of that guest and the
39 cpu_pid array contains the VCPU to host process mapping. The array is
40 of size vcpu_count where the index is VCPU and the value is the process
41 ID (PID) of the host process, running that VCPU. The name, vcpu_count
42 and cpu_pid values must not be freed.
43
45 The tracecmd_get_traceid() function returns a 64 bit trace ID.
46 The tracecmd_get_guest_cpumap() function returns -1 in case of an error
48 or 0 otherwise. If 0 is returned, then the name, vcpu_count and cpu_pid
49 parameters contain the requested information.
50
52 #include <trace-cmd.h>
53 ...
54 struct tracecmd_input *host = tracecmd_open("trace.dat");
55 if (!host) {
56 /* Failed to open host trace file */
57 }
58 struct tracecmd_input *guest1 = tracecmd_open_head("trace-Guest1.dat");
60 if (!guest1) {
61 /* Failed to open guest1 trace file */
62 }
63 struct tracecmd_input *guest2 = tracecmd_open_head("trace-Guest2.dat");
64 if (!guest2) {
65 /* Failed to open guest2 trace file */
66 }
67 unsigned long long guest_id_1 = tracecmd_get_traceid(guest1);
69 unsigned long long guest_id_2 = tracecmd_get_traceid(guest2);
70 int *cpu_pid_1, *cpu_pid_2;
71 int vcount_1, vcount_2;
72 char *name_1, *name_2;
73 if (!tracecmd_get_guest_cpumap(host, guest_id_1, &name_1, &vcount_1, &cpu_pid_1)) {
75 /* The Host and a guest1 with name_1 are part of the same trace session.
76 * Got guest1 VCPU to host PID mapping.
77 */
78 }
79 if (!tracecmd_get_guest_cpumap(host, guest_id_2, &name_2, &vcount_2, &cpu_pid_2)) {
80 /* The Host and a guest2 with name_2 are part of the same trace session.
81 * Got guest2 VCPU to host PID mapping.
82 */
83 }
84 ...
85 tracecmd_close(guest1);
86 tracecmd_close(guest2);
87 tracecmd_close(handle);
88
90 trace-cmd.h
91 Header file to include in order to have access to the library APIs.
92 -ltracecmd
93 Linker switch to add when building a program that uses the library.
94
96 libtracefs(3), libtraceevent(3), trace-cmd(1) trace-cmd.dat(5)
97
99 Steven Rostedt <rostedt@goodmis.org[1]>
100 Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>
101
103 Report bugs to <linux-trace-devel@vger.kernel.org[3]>
104
106 libtracecmd is Free Software licensed under the GNU LGPL 2.1
107
109 https://git.kernel.org/pub/scm/utils/trace-cmd/trace-cmd.git/
110
112 Copyright (C) 2020 VMware, Inc. Free use of this software is granted
113 under the terms of the GNU Public License (GPL).
114
116 1. rostedt@goodmis.org
117 mailto:rostedt@goodmis.org
118 2. tz.stoyanov@gmail.com
120 mailto:tz.stoyanov@gmail.com
121 3. linux-trace-devel@vger.kernel.org
123 mailto:linux-trace-devel@vger.kernel.org
124libtracefs 03/29/2021 LIBTRACECMD(3)