SYNOPSIS
#include <tracefs.h> char *tracefs_find_cid_pid(int cid); char *tracefs_instance_find_cid_pid(struct tracefs_instance *instance, int cid); int tracefs_time_conversion(int cpu, int *shift, int *multi, long long *offset);
DESCRIPTION
The tracefs_find_cid_pid() will use tracing to follow the wakeups of connecting to the given cid in order to find the pid of the guest thread that belongs to the vsocket cid. It will then read the proc file system to find the thread leader, and it will return the pid of the thread leader.
The tracefs_instance_find_cid_pid() is the same as tracefs_find_cid_pid() but defines the instance to use to perform the tracing in. If NULL it will use the top level buffer to perform the tracing.
The tracefs_time_conversion() will return the values used by the kernel to convert the raw time stamp counter into nanoseconds for the given cpu. Pointers for shift, multi and offset can be NULL to be ignored, otherwise they are set with the shift, multiplier and offset repectively.
RETURN VALUE
Both tracefs_find_cid_pid() and tracefs_instance_find_cid_pid() will return the pid of the guest main thread that belongs to the cid, or -1 on error (or not found).
EXAMPLE
#include <stdlib.h> #include <unistd.h> #include <tracefs.h> #define MAX_CID 256 static void find_cid(struct tracefs_instance *instance, int cid) { int pid; pid = tracefs_instance_find_cid_pid(instance, cid); if (pid >= 0) printf("%d\t%d\n", cid, pid); } static int find_cids(void) { struct tracefs_instance *instance; char *name; int cid; int ret; ret = asprintf(&name, "vsock_find-%d\n", getpid()); if (ret < 0) return ret; instance = tracefs_instance_create(name); free(name); if (!instance) return -1; for (cid = 0; cid < MAX_CID; cid++) find_cid(instance, cid); tracefs_event_disable(instance, NULL, NULL); tracefs_instance_destroy(instance); tracefs_instance_free(instance); return 0; } struct time_info { int shift; int multi; }; static void show_time_conversion(void) { struct time_info *tinfo; int cpus; int cpu; int ret; cpus = sysconf(_SC_NPROCESSORS_CONF); tinfo = calloc(cpus, sizeof(*tinfo)); if (!tinfo) exit(-1); for (cpu = 0; cpu < cpus; cpu++) { ret = tracefs_time_conversion(cpu, &tinfo[cpu].shift, &tinfo[cpu].multi, NULL); if (ret) break; } if (cpu != cpus) { if (!cpu) { perror("tracefs_time_conversion"); exit(-1); } printf("Only read %d of %d CPUs", cpu, cpus); cpus = cpu + 1; } /* Check if all the shift and mult values are the same */ for (cpu = 1; cpu < cpus; cpu++) { if (tinfo[cpu - 1].shift != tinfo[cpu].shift) break; if (tinfo[cpu - 1].multi != tinfo[cpu].multi) break; } if (cpu == cpus) { printf("All cpus have:\n"); printf(" shift: %d\n", tinfo[0].shift); printf(" multi: %d\n", tinfo[0].multi); printf("\n"); return; } for (cpu = 0; cpu < cpus; cpu++) { printf("CPU: %d\n", cpu); printf(" shift: %d\n", tinfo[cpu].shift); printf(" multi: %d\n", tinfo[cpu].multi); printf("\n"); } } int main(int argc, char *argv[]) { show_time_conversion(); find_cids(); exit(0); }
FILES
tracefs.h
Header file to include in order to have access to the library APIs.
-ltracefs
Linker switch to add when building a program that uses the library.
SEE ALSO
libtracefs(3), libtraceevent(3), trace-cmd(1)
AUTHOR
Steven Rostedt <rostedt@goodmis.org> Tzvetomir Stoyanov <tz.stoyanov@gmail.com>
REPORTING BUGS
Report bugs to <linux-trace-devel@vger.kernel.org>
LICENSE
libtracefs is Free Software licensed under the GNU LGPL 2.1
COPYING
Copyright (C) 2020 VMware, Inc. Free use of this software is granted under the terms of the GNU Public License (GPL).