ограничить процессы подмножествами процессоров и узлов памяти (confine processes to processor and memory node subsets)
Имя (Name)
cpuset - confine processes to processor and memory node subsets
Описание (Description)
The cpuset filesystem is a pseudo-filesystem interface to the
kernel cpuset mechanism, which is used to control the processor
placement and memory placement of processes. It is commonly
mounted at /dev/cpuset.
On systems with kernels compiled with built in support for
cpusets, all processes are attached to a cpuset, and cpusets are
always present. If a system supports cpusets, then it will have
the entry nodev cpuset in the file /proc/filesystems. By
mounting the cpuset filesystem (see the EXAMPLES section below),
the administrator can configure the cpusets on a system to
control the processor and memory placement of processes on that
system. By default, if the cpuset configuration on a system is
not modified or if the cpuset filesystem is not even mounted,
then the cpuset mechanism, though present, has no effect on the
system's behavior.
A cpuset defines a list of CPUs and memory nodes.
The CPUs of a system include all the logical processing units on
which a process can execute, including, if present, multiple
processor cores within a package and Hyper-Threads within a
processor core. Memory nodes include all distinct banks of main
memory; small and SMP systems typically have just one memory node
that contains all the system's main memory, while NUMA (non-
uniform memory access) systems have multiple memory nodes.
Cpusets are represented as directories in a hierarchical pseudo-
filesystem, where the top directory in the hierarchy
(/dev/cpuset) represents the entire system (all online CPUs and
memory nodes) and any cpuset that is the child (descendant) of
another parent cpuset contains a subset of that parent's CPUs and
memory nodes. The directories and files representing cpusets
have normal filesystem permissions.
Every process in the system belongs to exactly one cpuset. A
process is confined to run only on the CPUs in the cpuset it
belongs to, and to allocate memory only on the memory nodes in
that cpuset. When a process fork(2)s, the child process is
placed in the same cpuset as its parent. With sufficient
privilege, a process may be moved from one cpuset to another and
the allowed CPUs and memory nodes of an existing cpuset may be
changed.
When the system begins booting, a single cpuset is defined that
includes all CPUs and memory nodes on the system, and all
processes are in that cpuset. During the boot process, or later
during normal system operation, other cpusets may be created, as
subdirectories of this top cpuset, under the control of the
system administrator, and processes may be placed in these other
cpusets.
Cpusets are integrated with the sched_setaffinity(2) scheduling
affinity mechanism and the mbind(2) and set_mempolicy(2) memory-
placement mechanisms in the kernel. Neither of these mechanisms
let a process make use of a CPU or memory node that is not
allowed by that process's cpuset. If changes to a process's
cpuset placement conflict with these other mechanisms, then
cpuset placement is enforced even if it means overriding these
other mechanisms. The kernel accomplishes this overriding by
silently restricting the CPUs and memory nodes requested by these
other mechanisms to those allowed by the invoking process's
cpuset. This can result in these other calls returning an error,
if for example, such a call ends up requesting an empty set of
CPUs or memory nodes, after that request is restricted to the
invoking process's cpuset.
Typically, a cpuset is used to manage the CPU and memory-node
confinement for a set of cooperating processes such as a batch
scheduler job, and these other mechanisms are used to manage the
placement of individual processes or memory regions within that
set or job.
