# tracefs_instance_set_affinity

## NAME



           tracefs_instance_set_affinity, tracefs_instance_set_affinity_set,
           tracefs_instance_set_affinity_raw, tracefs_instance_get_affinity,
           tracefs_instance_get_affinity_set,
           tracefs_instance_get_affinity_raw - Sets or retrieves the affinity
           for an instance or top level for what CPUs enable tracing.
    


## SYNOPSIS



           **#include <tracefs.h>**
    
           int **tracefs_instance_set_affinity**(struct tracefs_instance *_instance_ , const char *_cpu_str_);
           int **tracefs_instance_set_affinity_set**(struct tracefs_instance *_instance_ , cpu_set_t *_set_ , size_t _set_size_);
           int **tracefs_instance_set_affinity_raw**(struct tracefs_instance *_instance_ , const char *_mask_);
    
           char * **tracefs_instance_get_affinity**(struct tracefs_instance *_instance_);
           int **tracefs_instance_get_affinity_set**(struct tracefs_instance *_instance_ , cpu_set_t *_set_ , size_t _set_size_);
           char * **tracefs_instance_get_affinity_raw**(struct tracefs_instance *_instance_);
    


## DESCRIPTION



           These functions set or retrieve the CPU affinity that limits what
           CPUs will have tracing enabled for a given instance defined by the
           _instance_ parameter. If _instance_ is NULL, then the top level
           instance is affected.
    
           The **tracefs_instance_set_affinity()** function takes a string
           _cpu_str_ that is a list of CPUs to set the affinity for. If _cpu_str_
           is NULL, then all the CPUs in the system will be set. The format
           of _cpu_str_ is a comma delimited string of decimal numbers with no
           spaces. A range may be specified by a hyphen.
    
           For example: "1,4,6-8"
    
           The numbers do not need to be in order except for ranges, where
           the second number must be equal to or greater than the first.
    
           The **tracefs_instance_set_affinity_set()** function takes a CPU set
           defined by CPU_SET(3). The size of the set defined by _set_size_ is
           the size in bytes of _set_. If _set_ is NULL then all the CPUs on the
           system will be set, and _set_size_ is ignored.
    
           The **tracefs_instance_set_affinity_raw()** function takes a string
           that holds a hexidecimal bitmask, where each 32 bits is separated
           by a comma. For a machine with more that 32 CPUs, to set CPUS 1-10
           and CPU 40:
    
               "100,000007fe"
    
           Where the above is a hex representation of bits 1-10 and bit 40
           being set.
    
           The **tracefs_instance_get_affinity()** will retrieve the affinity in
           a human readable form.
    
           For example: "1,4,6-8"
    
           The string returned must be freed with free(3).
    
           The **tracefs_instance_get_affinity_set()** will set all the bits in
           the passed in cpu set (from CPU_SET(3)). Note it will not clear
           any bits that are already set in the set but the CPUs are not. If
           only the bits for the CPUs that are enabled should be set, a
           CPU_ZERO_S() should be performed on the set before calling this
           function.
    
           The **tracefs_instance_get_affinity_raw()** will simply read the
           instance tracing_cpumask and return that string. The returned
           string must be freed with free(3).
    


## RETURN VALUE



           All the set functions return 0 on success and -1 on error.
    
           The functions **tracefs_instance_get_affinity()** and
           **tracefs_instance_get_affinity_raw()** returns an allocated string
           that must be freed with free(3), or NULL on error.
    
           The function **tracefs_instance_get_affinity_set()** returns the
           number of CPUs that were found set, or -1 on error.
    


## ERRORS



           The following errors are for all the above calls:
    
           **EFBIG** if a CPU is set that is greater than what is in the system.
    
           **EINVAL** One of the parameters was invalid.
    
           The following errors are for **tracefs_instance_set_affinity**() and
           **tracefs_instance_set_affinity_set**():
    
           **ENOMEM** Memory allocation error.
    
           **ENODEV** dynamic events of requested type are not configured for the
           running kernel.
    
           The following errors are just for **tracefs_instance_set_affinity**()
    
           **EACCES** The _cpu_str_ was modified by another thread when processing
           it.
    


## EXAMPLE



               #include <sched.h>
               #include <stdio.h>
               #include <stdlib.h>
               #include <tracefs.h>
    
               int main (int argc, char **argv)
               {
                       struct trace_seq seq;
                       cpu_set_t *set;
                       size_t set_size;
                       char *c;
                       int cpu1;
                       int cpu2;
                       int i;
    
                       c = tracefs_instance_get_affinity(NULL);
                       printf("The affinity was %s\n", c);
                       free(c);
    
                       if (argc < 2) {
                               tracefs_instance_set_affinity(NULL, NULL);
                               exit(0);
                       }
                       /* Show example using a set */
                       if (argc == 2 && !strchr(argv[1],',')) {
                               cpu1 = atoi(argv[1]);
                               c = strchr(argv[1], '-');
                               if (c++)
                                       cpu2 = atoi(c);
                               else
                                       cpu2 = cpu1;
                               if (cpu2 < cpu1) {
                                       fprintf(stderr, "Invalid CPU range\n");
                                       exit(-1);
                               }
                               set = CPU_ALLOC(cpu2 + 1);
                               set_size = CPU_ALLOC_SIZE(cpu2 + 1);
                               CPU_ZERO_S(set_size, set);
                               for ( ; cpu1 <= cpu2; cpu1++)
                                       CPU_SET(cpu1, set);
                               tracefs_instance_set_affinity_set(NULL, set, set_size);
                               CPU_FREE(set);
                               exit(0);
                       }
    
                       trace_seq_init(&seq);
                       for (i = 1; i < argc; i++) {
                               if (i > 1)
                                       trace_seq_putc(&seq, ',');
                               trace_seq_puts(&seq, argv[i]);
                       }
                       trace_seq_terminate(&seq);
                       tracefs_instance_set_affinity(NULL, seq.buffer);
                       trace_seq_destroy(&seq);
                       exit(0);
    
                       return 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.
    


## LICENSE



           libtracefs is Free Software licensed under the GNU LGPL 2.1
    


## RESOURCES



           **https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.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
    


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