mirror of https://github.com/mkerrisk/man-pages
cgroups.7: Restructure list of cgroup v2 differences
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
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@ -450,10 +450,38 @@ mounted under the v1 and v2 hierarchies,
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it is not possible to mount the same controller simultaneously
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it is not possible to mount the same controller simultaneously
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under both the v1 and the v2 hierarchies.
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under both the v1 and the v2 hierarchies.
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The new behaviors in cgroups v2 are summarized below:
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The new behaviors in cgroups v2 are summarized here,
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.TP 3
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and in some cases elaborated in the following subsections.
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1. Processes only in leaf nodes
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.IP 1. 3
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With the exception of the root cgroup, processes may reside only in leaf nodes.
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"Internal" processes are not permitted.
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With the exception of the root cgroup, processes may reside
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only in leaf nodes (cgroups that do not themselves contain child cgroups).
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.IP 2.
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Active cgroups must be specified via the files
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.IR cgroup.controllers
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and
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.IR cgroup.subtree_control .
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.IP 3.
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The
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.I tasks
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file has been removed.
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In addition, the
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.I cgroup.clone_children
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file that is employed by the
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.I cpuset
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controller has been removed.
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.IP 4.
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An improved mechanism for notification of empty cgroups is provided by the
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.IR cgroup.events
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file.
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.PP
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For more changes, see the
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.I Documentation/cgroup-v2.txt
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file in the kernel source.
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.\"
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.SS Cgroups v2 "no internal processes" rule
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With the exception of the root cgroup, processes may reside
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only in leaf nodes (cgroups that do not themselves contain child cgroups).
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This avoids the need to decide how to partition resources between
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This avoids the need to decide how to partition resources between
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processes which are members of cgroup A and processes in child cgroups of A.
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processes which are members of cgroup A and processes in child cgroups of A.
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@ -480,12 +508,8 @@ the relationship between processes in
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and
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and
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.IR /cg1 's
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.IR /cg1 's
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other children.
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other children.
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.TP
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.\"
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2. Active cgroups must be specified
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.SS Cgroups v2 subtree control
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The unified hierarchy presents two new files,
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.IR cgroup.controllers
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and
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.IR cgroup.subtree_control .
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When a cgroup
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When a cgroup
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.I A/b
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.I A/b
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is created, its
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is created, its
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@ -502,20 +526,6 @@ controller is not enabled in
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.IR /A/B ,
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.IR /A/B ,
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then it cannot be enabled in
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then it cannot be enabled in
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.IR /A/B/C .
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.IR /A/B/C .
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.TP
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3. No "tasks" or "cgroup.clone_children" files
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.TP
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4. Empty cgroup notification
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A new file,
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.IR cgroup.populated ,
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under each cgroup contains '0' when the
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cgroup is empty, and 1 when it is populated.
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It therefore may be watched to detect when a cgroup becomes (non-)empty.
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This replaces the original notify-on-release mechanism.
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.PP
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For more changes, see the
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.I Documentation/cgroup-v2.txt
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file in the kernel source.
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.\"
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.\"
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.SS Cgroups v2 events file
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.SS Cgroups v2 events file
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A new feature in cgroups v2 is the
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A new feature in cgroups v2 is the
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