NAME

       coresched - manage core scheduling cookies for tasks

SYNOPSIS

       coresched [get] [-s pid]

       coresched new [-t type] -d pid

       coresched new [-t type] -- command [argument...]

       coresched copy [-s pid] [-t type] -d pid

       coresched copy [-s pid] [-t type] -- command [argument...]

DESCRIPTION

       The coresched command is used to retrieve or modify the core scheduling cookies of a running process
       given its pid, or to spawn a new command with core scheduling cookies.

       Core scheduling permits the definition of groups of tasks that are allowed to share a physical core. This
       is done by assigning a cookie to each task. Only tasks have the same cookie are allowed to be scheduled
       on the same physical core.

       It is possible to either assign a new random cookie to a task, or copy a cookie from another task. It is
       not possible to choose the value of the cookie.

FUNCTIONS

       get
           Retrieve the core scheduling cookie of the PID specified in -s. If -s is omitted, it will get the
           cookie of the current coresched process.

       new
           Assign a new cookie to an existing PID specified in -d, or execute command with a new cookie.

       copy
           Copy the cookie from an existing PID (-s) to another PID (-d), or execute command with that cookie.
           If -s is omitted, it will get the cookie of the current coresched process.

       If no function is specified, it will run the get function.

OPTIONS

       -s, --source PID
           Which PID to get the cookie from. If this option is omitted, it will get the cookie from the current
           coresched process.

       -d, --dest PID
           Which PID to modify the cookie of.

       -t, --dest-type TYPE
           The type of the PID whose cookie will be modified. This can be one of three values:

           •   pid, or process ID

           •   tgid, or thread group ID (default value)

           •   pgid, or process group ID

       -v, --verbose
           Show extra information when modifying cookies of tasks.

       -h, --help
           Display help text and exit.

       -V, --version
           Display version and exit.

EXAMPLES

       Get the core scheduling cookie of the coresched task itself, usually inherited from its parent:
           coresched get

       Get the core scheduling cookie of a task with PID 123:
           coresched get -s 123

       Give a task with PID 123 a new core scheduling cookie:
           coresched new -d 123

       Spawn a new task with a new core scheduling cookie:
           coresched new -- command [argument...]

       Copy the cookie from the current coresched process another task with pid 456:
           coresched copy -d 456

       Copy the cookie from a task with pid 123 to another task with pid 456:
           coresched copy -s 123 -d 456

       Copy the cookie from a task with pid 123 to a new task command:
           coresched copy -s 123 -- command [argument...]

       Copy the cookie from a task with pid 123 to the process group ID 456:
           coresched copy -s 123 -t pgid -d 456

PERMISSIONS

       Retrieving or modifying the core scheduling cookie of a process requires PTRACE_MODE_READ_REALCREDS
       ptrace access to that process. See the section "Ptrace access mode checking" in ptrace(2) for more
       information.

RETURN VALUE

       On success, coresched returns 0. If coresched fails, it will print an error and return 1.

       If a command is being executed, the return value of coresched will be the return value of command.

NOTES

       coresched requires core scheduling support in the kernel. This can be enabled via the CONFIG_SCHED_CORE
       kernel config option.

AUTHORS

       Thijs Raymakers <thijs@raymakers.nl>, Phil Auld <pauld@redhat.com>

COPYRIGHT

       Copyright © 2024 Thijs Raymakers and Phil Auld. This is free software licensed under the EUPL.

SEE ALSO

       chrt(1), nice(1), renice(1), taskset(1), ptrace(2), sched(7)

       The Linux kernel source files Documentation/admin-guide/hw-vuln/core-scheduling.rst

REPORTING BUGS

       For bug reports, use the issue tracker <https://github.com/util-linux/util-linux/issues>.

AVAILABILITY

       The coresched command is part of the util-linux package which can be downloaded from Linux Kernel Archive
       <https://www.kernel.org/pub/linux/utils/util-linux/>.

util-linux 2.41                                    2025-02-26                                       CORESCHED(1)