__ROUND_JIFFIES_RELA(9) Driver Basics __ROUND_JIFFIES_RELA(9)NAME
__round_jiffies_relative - function to round jiffies to a full second
SYNOPSIS
unsigned long __round_jiffies_relative(unsigned long j, int cpu);
ARGUMENTS
j
the time in (relative) jiffies that should be rounded
cpu
the processor number on which the timeout will happen
DESCRIPTION
__round_jiffies_relative rounds a time delta in the future (in jiffies) up or down to (approximately) full seconds. This is useful for
timers for which the exact time they fire does not matter too much, as long as they fire approximately every X seconds.
By rounding these timers to whole seconds, all such timers will fire at the same time, rather than at various times spread out. The goal of
this is to have the CPU wake up less, which saves power.
The exact rounding is skewed for each processor to avoid all processors firing at the exact same time, which could lead to lock contention
or spurious cache line bouncing.
The return value is the rounded version of the j parameter.
COPYRIGHT Kernel Hackers Manual 3.10 June 2014 __ROUND_JIFFIES_RELA(9)
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assign_cpu_to_pset(3) Library Functions Manual assign_cpu_to_pset(3)NAME
assign_cpu_to_pset - Assigns a processor to a processor set
LIBRARY
Pset Library (libpset.a)
Mach Library (libmach.a)
SYNOPSIS
#include <sys/types.h> #include <sys/processor.h>
int assign_cpu_to_pset(
unsigned long cpu,
long pset_id ,
long option );
PARAMETERS
Processor or processors to assign to the specified processor set. Processor set identifier, which is returned by the create_pset function.
Specifies a bit mask. Currently, only the ANY_CPU bit is supported. If this bit is set, the value specified by the cpu variable is the
number of processors to be assigned to the specified processor set from the default processor set. If the ANY_CPU bit is not set, the
value specified by the cpu variable is the mask of processors to be assigned to the processor set.
DESCRIPTION
The assign_cpu_to_pset function removes processors from their current processor set and assigns them to the processor set specified by the
pset_id variable. This function requires root privileges.
If the ANY_CPU option is specified, the number of processors specified by the cpu variable are assigned from the default processor set to
the processor set that is specified with the pset_id variable. If the specified number of processors are not available in the default pro-
cessor set, an error is returned and no processors are assigned.
If the ANY_CPU option is not set, the value specified by the cpu variable is a mask of processors to be assigned to the specified processor
set. For example, if you specify a cpu value of 6, then processors 2 and 3 are assigned to the processor set.
Note that processors are not required to start in slot 0 on some platforms. For example, you may see a three-processor system with proces-
sors in slots 6, 7, and 8. The console assigns the master processor at power up, which is usually the processor in slot 0 if it is occu-
pied. However, there is no requirement that slot 0 must be populated or that the master is the first processor on the bus. In the example
of the three-processor (slots 6, 7, and 8) system, the master processor will be the one in slot 6.
Processor assignments are logged in the /var/adm/wtmp file.
RETURN VALUES
If the processor assignment is successful, the assign_cpu_to_pset function returns zero (0). If the assignment is unsuccessful, the func-
tion returns a negative number. Use the print_pset_error function to print a message that describes the error.
FILES
/var/adm/wtmp
RELATED INFORMATION bind_to_cpu(3), create_pset(3), destroy_pset(3), assign_pid_to_pset(3), print_pset_error(3), processor_sets(4), pset_create(1) delim off
assign_cpu_to_pset(3)