The nice(3) value of a process is one of the
factors used by the kernel to determine a process'
scheduling priority. Scheduling priorities typically range from -20
to +20. The higher (more positive) the value, the lower the
processes' scheduling priority, and the lower (more
negative) the value, the higher the command's
scheduling priority. Most processes (such as
sendmail) run with a
nice(3) value of zero.
At busy mail-handling sites, it can be desirable to process the
queues at a higher (less favorable) or lower (more favorable)
nice(3) priority than normal. If you run many
queue processors over many queues, you might wish to increase the
nice(3) value so that queue processing has less
impact on other processes. At mail-sending sites, where outbound
email has the priority, you might wish to decrease the
nice(3) value so that queue processing gets more
CPU time than other processes.
The nice(3) value for queue processors is set
with this NiceQueueRun option like this:
O NiceQueueRun=value configuration file (V8.12 and later)
-ONiceQueueRun=value command line (V8.12 and later)
define(`confNICE_QUEUE_RUN',`value') mc configuration (V8.12 and later)
Here, value is the value passed to the
nice(3) function. It is of type
numeric. A positive value will decrease the
queue runner's priorities. A negative value will be
silently accepted, then ignored at runtime. A nonnumeric or zero
value (the default) will leave the priority unchanged.
If your system lacks nice(3) support, the
following warning will be printed and logged and this
NiceQueueRun option will be ignored:
Warning: NiceQueueRun set on system that doesn't support nice( )
Note that the call to nice(3) does not check for
errors. If sendmail cannot set a new
nice(3) value, the queue processors will
silently not be given a new priority.
The NiceQueueRun option is not safe. If specified
from the command line, it can cause sendmail to
relinquish its special privileges.