'\" t
.\"     Title: coresched
.\"    Author: [see the "AUTHOR(S)" section]
.\" Generator: Asciidoctor 2.0.23
.\"      Date: 2025-03-29
.\"    Manual: User Commands
.\"    Source: util-linux 2.41
.\"  Language: English
.\"
.TH "CORESCHED" "1" "2025-03-29" "util\-linux 2.41" "User Commands"
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.SH "NAME"
coresched \- manage core scheduling cookies for tasks
.SH "SYNOPSIS"
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\fBcoresched\fP [\fBget\fP] [\fB\-s\fP \fIpid\fP]
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\fBcoresched\fP \fBnew\fP [\fB\-t\fP \fItype\fP] \fB\-d\fP \fIpid\fP
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\fBcoresched\fP \fBnew\fP [\fB\-t\fP \fItype\fP] \-\- \fIcommand\fP [\fIargument\fP...]
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\fBcoresched\fP \fBcopy\fP [\fB\-s\fP \fIpid\fP] [\fB\-t\fP \fItype\fP] \fB\-d\fP \fIpid\fP
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\fBcoresched\fP \fBcopy\fP [\fB\-s\fP \fIpid\fP] [\fB\-t\fP \fItype\fP] \-\- \fIcommand\fP [\fIargument\fP...]
.SH "DESCRIPTION"
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The \fBcoresched\fP command is used to retrieve or modify the core scheduling cookies of a running process given its \fIpid\fP, or to spawn a new \fIcommand\fP with core scheduling cookies.
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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.
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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.
.SH "FUNCTIONS"
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\fBget\fP
.RS 4
Retrieve the core scheduling cookie of the PID specified in \fB\-s\fP.
If \fB\-s\fP is omitted, it will get the cookie of the current \fBcoresched\fP process.
.RE
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\fBnew\fP
.RS 4
Assign a new cookie to an existing PID specified in \fB\-d\fP, or execute \fIcommand\fP with a new cookie.
.RE
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\fBcopy\fP
.RS 4
Copy the cookie from an existing PID (\fB\-s\fP) to another PID (\fB\-d\fP), or execute \fIcommand\fP with that cookie.
If \fB\-s\fP is omitted, it will get the cookie of the current \fBcoresched\fP process.
.RE
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If no function is specified, it will run the \fBget\fP function.
.SH "OPTIONS"
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\fB\-s\fP, \fB\-\-source\fP \fIPID\fP
.RS 4
Which \fIPID\fP to get the cookie from.
If this option is omitted, it will get the cookie from the current \fBcoresched\fP process.
.RE
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\fB\-d\fP, \fB\-\-dest\fP \fIPID\fP
.RS 4
Which \fIPID\fP to modify the cookie of.
.RE
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\fB\-t\fP, \fB\-\-dest\-type\fP \fITYPE\fP
.RS 4
The type of the PID whose cookie will be modified. This can be one of three values:
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.RS 4
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\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.  sp -1
.  IP \(bu 2.3
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\fBpid\fP, or process ID
.RE
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.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
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.el \{\
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.  IP \(bu 2.3
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\fBtgid\fP, or thread group ID (default value)
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.  sp -1
.  IP \(bu 2.3
.\}
\fBpgid\fP, or process group ID
.RE
.RE
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\fB\-v\fP, \fB\-\-verbose\fP
.RS 4
Show extra information when modifying cookies of tasks.
.RE
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\fB\-h\fP, \fB\-\-help\fP
.RS 4
Display help text and exit.
.RE
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\fB\-V\fP, \fB\-\-version\fP
.RS 4
Display version and exit.
.RE
.SH "EXAMPLES"
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Get the core scheduling cookie of the coresched task itself, usually inherited from its parent:
.RS 4
\fBcoresched get\fP
.RE
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Get the core scheduling cookie of a task with PID \fI123\fP:
.RS 4
\fBcoresched get \-s\fP \fI123\fP
.RE
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Give a task with PID \fI123\fP a new core scheduling cookie:
.RS 4
\fBcoresched new \-d\fP \fI123\fP
.RE
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Spawn a new task with a new core scheduling cookie:
.RS 4
\fBcoresched new\fP \-\- \fIcommand\fP [\fIargument\fP...]
.RE
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Copy the cookie from the current coresched process another task with pid \fI456\fP:
.RS 4
\fBcoresched copy \-d\fP \fI456\fP
.RE
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Copy the cookie from a task with pid \fI123\fP to another task with pid \fI456\fP:
.RS 4
\fBcoresched copy \-s\fP \fI123\fP \fB\-d\fP \fI456\fP
.RE
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Copy the cookie from a task with pid \fI123\fP to a new task \fIcommand\fP:
.RS 4
\fBcoresched copy \-s\fP \fI123\fP \-\- \fIcommand\fP [\fIargument\fP...]
.RE
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Copy the cookie from a task with pid \fI123\fP to the process group ID \fI456\fP:
.RS 4
\fBcoresched copy \-s\fP \fI123\fP \fB\-t\fP \fIpgid\fP \fB\-d\fP \fI456\fP
.RE
.SH "PERMISSIONS"
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Retrieving or modifying the core scheduling cookie of a process requires \fBPTRACE_MODE_READ_REALCREDS\fP ptrace access to that process.
See the section "Ptrace access mode checking" in \fBptrace\fP(2) for more information.
.SH "RETURN VALUE"
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On success, \fBcoresched\fP returns 0.
If \fBcoresched\fP fails, it will print an error and return 1.
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If a \fIcommand\fP is being executed, the return value of \fBcoresched\fP will be the return value of \fIcommand\fP.
.SH "NOTES"
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\fBcoresched\fP requires core scheduling support in the kernel.
This can be enabled via the \fBCONFIG_SCHED_CORE\fP kernel config option.
.SH "AUTHORS"
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.MTO "thijs\(atraymakers.nl" "Thijs Raymakers" ","
.MTO "pauld\(atredhat.com" "Phil Auld" ""
.SH "COPYRIGHT"
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Copyright © 2024 Thijs Raymakers and Phil Auld. This is free software licensed under the EUPL.
.SH "SEE ALSO"
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\fBchrt\fP(1),
\fBnice\fP(1),
\fBrenice\fP(1),
\fBtaskset\fP(1),
\fBptrace\fP(2),
\fBsched\fP(7)
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The Linux kernel source files \fIDocumentation/admin\-guide/hw\-vuln/core\-scheduling.rst\fP
.SH "REPORTING BUGS"
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For bug reports, use the \c
.URL "https://github.com/util\-linux/util\-linux/issues" "issue tracker" "."
.SH "AVAILABILITY"
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The \fBcoresched\fP command is part of the util\-linux package which can be downloaded from \c
.URL "https://www.kernel.org/pub/linux/utils/util\-linux/" "Linux Kernel Archive" "."