| libtracecmd(3) |
| ============= |
| |
| NAME |
| ---- |
| tracecmd_get_traceid, tracecmd_get_guest_cpumap - Manage trace session with multiple trace peers, |
| recorded in multiple trace files. |
| |
| SYNOPSIS |
| -------- |
| [verse] |
| -- |
| *#include <trace-cmd.h>* |
| |
| unsigned long long *tracecmd_get_traceid*(struct tracecmd_input pass:[*]_handle_); |
| int *tracecmd_get_guest_cpumap*(struct tracecmd_input pass:[*]_handle_, unsigned long long _trace_id_, const char pass:[*]pass:[*]_name_, int pass:[*]_vcpu_count_, const int pass:[*]pass:[*]_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 |
| ------- |
| [source,c] |
| -- |
| #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 |
| ----- |
| [verse] |
| -- |
| *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 |
| ------ |
| [verse] |
| -- |
| *Steven Rostedt* <[email protected]> |
| *Tzvetomir Stoyanov* <[email protected]> |
| -- |
| REPORTING BUGS |
| -------------- |
| Report bugs to <[email protected]> |
| |
| 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). |
