What's the meaning of parameter Priority_boost

Question

I have searched the web for answers to this. In auditd configuration file auditd.conf there is a parameter priority_boost. The RedHat manpage says:

priority_boost
This is a non-negative number that tells the audit daemon how much of a priority boost it should take. The default is 4. No change is 0.

I have difficulty understanding what impact the value has. Can someone shed some light on it?

score 2 · Accepted Answer · answered May 10 '20 at 10:25

Through auditd's source, priority_boost is used to modify auditd process nice value. The larger this value is, the higher priority of auditd is.

Here's the snippet of auditd's source:

...

if (config.priority_boost != 0) {
errno = 0;
rc = nice((int)-config.priority_boost);
if (rc == -1 && errno) {
    audit_msg(LOG_ERR, "Cannot change priority (%s)", 
        strerror(errno));
    free_config(&config);
    return 1;
}

...

And the snippet from nice(1) man page:

nice() adds inc to the nice value for the calling process. (A higher nice value means a low priority.) Only the superuser may specify a negative increment, or priority increase.

Please note that in the auditd snippet, nice is set to (int)-config.priority_boost, so that means if you set priority_boost to 4, you effectively set its nice to -4, hence higher priority.

Thanks for clarification! – PartyParrot May 10 '20 at 19:13 — PartyParrot, May 10 '20 at 19:13

What's the meaning of parameter Priority_boost

1 Answers1