core: make settings for unified cgroup hierarchy supersede the ones for legacy hierarchy (#4269)

There are overlapping control group resource settings for the unified and
legacy hierarchies.  To help transition, the settings are translated back and
forth.  When both versions of a given setting are present, the one matching the
cgroup hierarchy type in use is used.  Unfortunately, this is more confusing to
use and document than necessary because there is no clear static precedence.

Update the translation logic so that the settings for the unified hierarchy are
always preferred.  systemd.resource-control man page is updated to reflect the
change and reorganized so that the deprecated settings are at the end in its
own section.

1 files changed, 166 insertions, 159 deletions

diff --git a/man/systemd.resource-control.xml b/man/systemd.resource-control.xml
index c11f420fe5..10aefbe0c5 100644
--- a/man/systemd.resource-control.xml
+++ b/man/systemd.resource-control.xml
@@ -140,10 +140,10 @@
       </variablelist>
     </para>
 
-    <para>To ease the transition, there is best-effort translation between the two versions of settings. If all
-    settings of a unit for a given resource type are for the other hierarchy type, the settings are translated and
-    applied. If there are any valid settings for the hierarchy in use, all translations are disabled for the resource
-    type. Mixing the two types of settings on a unit can lead to confusing results.</para>
+    <para>To ease the transition, there is best-effort translation between the two versions of settings. For each
+    controller, if any of the settings for the unified hierarchy are present, all settings for the legacy hierarchy are
+    ignored. If the resulting settings are for the other type of hierarchy, the configurations are translated before
+    application.</para>
 
     <para>Legacy control group hierarchy (see <ulink
     url="https://www.kernel.org/doc/Documentation/cgroup-v1/cgroups.txt">cgroups.txt</ulink>), also called cgroup-v1,
@@ -196,30 +196,7 @@
 
           <para>Implies <literal>CPUAccounting=true</literal>.</para>
 
-          <para>These settings are supported only if the unified control group hierarchy is used.</para>
-        </listitem>
-      </varlistentry>
-
-      <varlistentry>
-        <term><varname>CPUShares=<replaceable>weight</replaceable></varname></term>
-        <term><varname>StartupCPUShares=<replaceable>weight</replaceable></varname></term>
-
-        <listitem>
-          <para>Assign the specified CPU time share weight to the processes executed. These options take an integer
-          value and control the <literal>cpu.shares</literal> control group attribute. The allowed range is 2 to
-          262144. Defaults to 1024. For details about this control group attribute, see <ulink
-          url="https://www.kernel.org/doc/Documentation/scheduler/sched-design-CFS.txt">sched-design-CFS.txt</ulink>.
-          The available CPU time is split up among all units within one slice relative to their CPU time share
-          weight.</para>
-
-          <para>While <varname>StartupCPUShares=</varname> only applies to the startup phase of the system,
-          <varname>CPUShares=</varname> applies to normal runtime of the system, and if the former is not set also to
-          the startup phase. Using <varname>StartupCPUShares=</varname> allows prioritizing specific services at
-          boot-up differently than during normal runtime.</para>
-
-          <para>Implies <literal>CPUAccounting=true</literal>.</para>
-
-          <para>These settings are supported only if the legacy control group hierarchy is used.</para>
+          <para>These settings replace <varname>CPUShares=</varname> and <varname>StartupCPUShares=</varname>.</para>
         </listitem>
       </varlistentry>
 
@@ -239,8 +216,6 @@
           20% CPU time on one CPU.</para>
 
           <para>Implies <literal>CPUAccounting=true</literal>.</para>
-
-          <para>This setting is supported on both unified and legacy control group hierarchies.</para>
         </listitem>
       </varlistentry>
 
@@ -276,7 +251,8 @@
 
           <para>Implies <literal>MemoryAccounting=true</literal>.</para>
 
-          <para>This setting is supported only if the unified control group hierarchy is used.</para>
+          <para>This setting is supported only if the unified control group hierarchy is used and disables
+          <varname>MemoryLimit=</varname>.</para>
         </listitem>
       </varlistentry>
 
@@ -298,7 +274,8 @@
 
           <para>Implies <literal>MemoryAccounting=true</literal>.</para>
 
-          <para>This setting is supported only if the unified control group hierarchy is used.</para>
+          <para>This setting is supported only if the unified control group hierarchy is used and disables
+          <varname>MemoryLimit=</varname>.</para>
         </listitem>
       </varlistentry>
 
@@ -320,8 +297,7 @@
 
           <para>Implies <literal>MemoryAccounting=true</literal>.</para>
 
-          <para>This setting is supported only if the unified control group hierarchy is used. Use
-          <varname>MemoryLimit=</varname> on systems using the legacy control group hierarchy.</para>
+          <para>This setting replaces <varname>MemoryLimit=</varname>.</para>
         </listitem>
       </varlistentry>
 
@@ -339,28 +315,8 @@
 
           <para>Implies <literal>MemoryAccounting=true</literal>.</para>
 
-          <para>This setting is supported only if the unified control group hierarchy is used.</para>
-        </listitem>
-      </varlistentry>
-
-      <varlistentry>
-        <term><varname>MemoryLimit=<replaceable>bytes</replaceable></varname></term>
-
-        <listitem>
-          <para>Specify the limit on maximum memory usage of the executed processes. The limit specifies how much
-          process and kernel memory can be used by tasks in this unit. Takes a memory size in bytes. If the value is
-          suffixed with K, M, G or T, the specified memory size is parsed as Kilobytes, Megabytes, Gigabytes, or
-          Terabytes (with the base 1024), respectively. Alternatively, a percentage value may be specified, which is
-          taken relative to the installed physical memory on the system. If assigned the special value
-          <literal>infinity</literal>, no memory limit is applied. This controls the
-          <literal>memory.limit_in_bytes</literal> control group attribute. For details about this control group
-          attribute, see <ulink
-          url="https://www.kernel.org/doc/Documentation/cgroup-v1/memory.txt">memory.txt</ulink>.</para>
-
-          <para>Implies <literal>MemoryAccounting=true</literal>.</para>
-
-          <para>This setting is supported only if the legacy control group hierarchy is used. Use
-          <varname>MemoryMax=</varname> on systems using the unified control group hierarchy.</para>
+          <para>This setting is supported only if the unified control group hierarchy is used and disables
+          <varname>MemoryLimit=</varname>.</para>
         </listitem>
       </varlistentry>
 
@@ -412,8 +368,8 @@
           in
           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 
-          <para>This setting is supported only if the unified control group hierarchy is used. Use
-          <varname>BlockIOAccounting=</varname> on systems using the legacy control group hierarchy.</para>
+          <para>This setting replaces <varname>BlockIOAccounting=</varname> and disables settings prefixed with
+          <varname>BlockIO</varname> or <varname>StartupBlockIO</varname>.</para>
         </listitem>
       </varlistentry>
 
@@ -438,9 +394,8 @@
 
           <para>Implies <literal>IOAccounting=true</literal>.</para>
 
-          <para>This setting is supported only if the unified control group hierarchy is used. Use
-          <varname>BlockIOWeight=</varname> and <varname>StartupBlockIOWeight=</varname> on systems using the legacy
-          control group hierarchy.</para>
+          <para>These settings replace <varname>BlockIOWeight=</varname> and <varname>StartupBlockIOWeight=</varname>
+          and disable settings prefixed with <varname>BlockIO</varname> or <varname>StartupBlockIO</varname>.</para>
         </listitem>
       </varlistentry>
 
@@ -459,8 +414,8 @@
 
           <para>Implies <literal>IOAccounting=true</literal>.</para>
 
-          <para>This setting is supported only if the unified control group hierarchy is used. Use
-          <varname>BlockIODeviceWeight=</varname> on systems using the legacy control group hierarchy.</para>
+          <para>This setting replaces <varname>BlockIODeviceWeight=</varname> and disables settings prefixed with
+          <varname>BlockIO</varname> or <varname>StartupBlockIO</varname>.</para>
         </listitem>
       </varlistentry>
 
@@ -484,8 +439,9 @@
 
           <para>Implies <literal>IOAccounting=true</literal>.</para>
 
-          <para>This setting is supported only if the unified control group hierarchy is used. Use
-          <varname>BlockIOAccounting=</varname> on systems using the legacy control group hierarchy.</para>
+          <para>These settings replace <varname>BlockIOReadBandwidth=</varname> and
+          <varname>BlockIOWriteBandwidth=</varname> and disable settings prefixed with <varname>BlockIO</varname> or
+          <varname>StartupBlockIO</varname>.</para>
         </listitem>
       </varlistentry>
 
@@ -509,100 +465,8 @@
 
           <para>Implies <literal>IOAccounting=true</literal>.</para>
 
-          <para>This setting is supported only if the unified control group hierarchy is used.</para>
-        </listitem>
-      </varlistentry>
-
-      <varlistentry>
-        <term><varname>BlockIOAccounting=</varname></term>
-
-        <listitem>
-          <para>Turn on Block I/O accounting for this unit, if the legacy control group hierarchy is used on the
-          system. Takes a boolean argument. Note that turning on block I/O accounting for one unit will also implicitly
-          turn it on for all units contained in the same slice and all for its parent slices and the units contained
-          therein. The system default for this setting may be controlled with
-          <varname>DefaultBlockIOAccounting=</varname> in
-          <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
-
-          <para>This setting is supported only if the legacy control group hierarchy is used. Use
-          <varname>IOAccounting=</varname> on systems using the unified control group hierarchy.</para>
-        </listitem>
-      </varlistentry>
-
-      <varlistentry>
-        <term><varname>BlockIOWeight=<replaceable>weight</replaceable></varname></term>
-        <term><varname>StartupBlockIOWeight=<replaceable>weight</replaceable></varname></term>
-
-        <listitem><para>Set the default overall block I/O weight for the executed processes, if the legacy control
-        group hierarchy is used on the system. Takes a single weight value (between 10 and 1000) to set the default
-        block I/O weight. This controls the <literal>blkio.weight</literal> control group attribute, which defaults to
-        500. For details about this control group attribute, see <ulink
-        url="https://www.kernel.org/doc/Documentation/cgroup-v1/blkio-controller.txt">blkio-controller.txt</ulink>.
-        The available I/O bandwidth is split up among all units within one slice relative to their block I/O
-        weight.</para>
-
-        <para>While <varname>StartupBlockIOWeight=</varname> only
-        applies to the startup phase of the system,
-        <varname>BlockIOWeight=</varname> applies to the later runtime
-        of the system, and if the former is not set also to the
-        startup phase. This allows prioritizing specific services at
-        boot-up differently than during runtime.</para>
-
-        <para>Implies
-        <literal>BlockIOAccounting=true</literal>.</para>
-
-        <para>This setting is supported only if the legacy control group hierarchy is used. Use
-        <varname>IOWeight=</varname> and <varname>StartupIOWeight=</varname> on systems using the unified control group
-        hierarchy.</para>
-
-      </listitem>
-      </varlistentry>
-
-      <varlistentry>
-        <term><varname>BlockIODeviceWeight=<replaceable>device</replaceable> <replaceable>weight</replaceable></varname></term>
-
-        <listitem>
-          <para>Set the per-device overall block I/O weight for the executed processes, if the legacy control group
-          hierarchy is used on the system. Takes a space-separated pair of a file path and a weight value to specify
-          the device specific weight value, between 10 and 1000. (Example: "/dev/sda 500"). The file path may be
-          specified as path to a block device node or as any other file, in which case the backing block device of the
-          file system of the file is determined. This controls the <literal>blkio.weight_device</literal> control group
-          attribute, which defaults to 1000. Use this option multiple times to set weights for multiple devices. For
-          details about this control group attribute, see <ulink
-          url="https://www.kernel.org/doc/Documentation/cgroup-v1/blkio-controller.txt">blkio-controller.txt</ulink>.</para>
-
-          <para>Implies
-          <literal>BlockIOAccounting=true</literal>.</para>
-
-          <para>This setting is supported only if the legacy control group hierarchy is used. Use
-          <varname>IODeviceWeight=</varname> on systems using the unified control group hierarchy.</para>
-        </listitem>
-      </varlistentry>
-
-      <varlistentry>
-        <term><varname>BlockIOReadBandwidth=<replaceable>device</replaceable> <replaceable>bytes</replaceable></varname></term>
-        <term><varname>BlockIOWriteBandwidth=<replaceable>device</replaceable> <replaceable>bytes</replaceable></varname></term>
-
-        <listitem>
-          <para>Set the per-device overall block I/O bandwidth limit for the executed processes, if the legacy control
-          group hierarchy is used on the system. Takes a space-separated pair of a file path and a bandwidth value (in
-          bytes per second) to specify the device specific bandwidth. The file path may be a path to a block device
-          node, or as any other file in which case the backing block device of the file system of the file is used. If
-          the bandwidth is suffixed with K, M, G, or T, the specified bandwidth is parsed as Kilobytes, Megabytes,
-          Gigabytes, or Terabytes, respectively, to the base of 1000. (Example:
-          "/dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0 5M"). This controls the
-          <literal>blkio.throttle.read_bps_device</literal> and <literal>blkio.throttle.write_bps_device</literal>
-          control group attributes. Use this option multiple times to set bandwidth limits for multiple devices. For
-          details about these control group attributes, see <ulink
-          url="https://www.kernel.org/doc/Documentation/cgroup-v1/blkio-controller.txt">blkio-controller.txt</ulink>.
-          </para>
-
-          <para>Implies
-          <literal>BlockIOAccounting=true</literal>.</para>
-
-          <para>This setting is supported only if the legacy control group hierarchy is used. Use
-          <varname>IOReadBandwidthMax=</varname> and <varname>IOWriteBandwidthMax=</varname> on systems using the
-          unified control group hierarchy.</para>
+          <para>These settings are supported only if the unified control group hierarchy is used and disable settings
+          prefixed with <varname>BlockIO</varname> or <varname>StartupBlockIO</varname>.</para>
         </listitem>
       </varlistentry>
 
@@ -734,6 +598,149 @@
   </refsect1>
 
   <refsect1>
+    <title>Deprecated Options</title>
+
+    <para>The following options are deprecated. Use the indicated superseding options instead:</para>
+
+    <variablelist class='unit-directives'>
+
+      <varlistentry>
+        <term><varname>CPUShares=<replaceable>weight</replaceable></varname></term>
+        <term><varname>StartupCPUShares=<replaceable>weight</replaceable></varname></term>
+
+        <listitem>
+          <para>Assign the specified CPU time share weight to the processes executed. These options take an integer
+          value and control the <literal>cpu.shares</literal> control group attribute. The allowed range is 2 to
+          262144. Defaults to 1024. For details about this control group attribute, see <ulink
+          url="https://www.kernel.org/doc/Documentation/scheduler/sched-design-CFS.txt">sched-design-CFS.txt</ulink>.
+          The available CPU time is split up among all units within one slice relative to their CPU time share
+          weight.</para>
+
+          <para>While <varname>StartupCPUShares=</varname> only applies to the startup phase of the system,
+          <varname>CPUShares=</varname> applies to normal runtime of the system, and if the former is not set also to
+          the startup phase. Using <varname>StartupCPUShares=</varname> allows prioritizing specific services at
+          boot-up differently than during normal runtime.</para>
+
+          <para>Implies <literal>CPUAccounting=true</literal>.</para>
+
+          <para>These settings are deprecated. Use <varname>CPUWeight=</varname> and
+          <varname>StartupCPUWeight=</varname> instead.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>MemoryLimit=<replaceable>bytes</replaceable></varname></term>
+
+        <listitem>
+          <para>Specify the limit on maximum memory usage of the executed processes. The limit specifies how much
+          process and kernel memory can be used by tasks in this unit. Takes a memory size in bytes. If the value is
+          suffixed with K, M, G or T, the specified memory size is parsed as Kilobytes, Megabytes, Gigabytes, or
+          Terabytes (with the base 1024), respectively. Alternatively, a percentage value may be specified, which is
+          taken relative to the installed physical memory on the system. If assigned the special value
+          <literal>infinity</literal>, no memory limit is applied. This controls the
+          <literal>memory.limit_in_bytes</literal> control group attribute. For details about this control group
+          attribute, see <ulink
+          url="https://www.kernel.org/doc/Documentation/cgroup-v1/memory.txt">memory.txt</ulink>.</para>
+
+          <para>Implies <literal>MemoryAccounting=true</literal>.</para>
+
+          <para>This setting is deprecated. Use <varname>MemoryMax=</varname> instead.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>BlockIOAccounting=</varname></term>
+
+        <listitem>
+          <para>Turn on Block I/O accounting for this unit, if the legacy control group hierarchy is used on the
+          system. Takes a boolean argument. Note that turning on block I/O accounting for one unit will also implicitly
+          turn it on for all units contained in the same slice and all for its parent slices and the units contained
+          therein. The system default for this setting may be controlled with
+          <varname>DefaultBlockIOAccounting=</varname> in
+          <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
+
+          <para>This setting is deprecated. Use <varname>IOAccounting=</varname> instead.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>BlockIOWeight=<replaceable>weight</replaceable></varname></term>
+        <term><varname>StartupBlockIOWeight=<replaceable>weight</replaceable></varname></term>
+
+        <listitem><para>Set the default overall block I/O weight for the executed processes, if the legacy control
+        group hierarchy is used on the system. Takes a single weight value (between 10 and 1000) to set the default
+        block I/O weight. This controls the <literal>blkio.weight</literal> control group attribute, which defaults to
+        500. For details about this control group attribute, see <ulink
+        url="https://www.kernel.org/doc/Documentation/cgroup-v1/blkio-controller.txt">blkio-controller.txt</ulink>.
+        The available I/O bandwidth is split up among all units within one slice relative to their block I/O
+        weight.</para>
+
+        <para>While <varname>StartupBlockIOWeight=</varname> only
+        applies to the startup phase of the system,
+        <varname>BlockIOWeight=</varname> applies to the later runtime
+        of the system, and if the former is not set also to the
+        startup phase. This allows prioritizing specific services at
+        boot-up differently than during runtime.</para>
+
+        <para>Implies
+        <literal>BlockIOAccounting=true</literal>.</para>
+
+        <para>These settings are deprecated. Use <varname>IOWeight=</varname> and <varname>StartupIOWeight=</varname>
+        instead.</para>
+
+      </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>BlockIODeviceWeight=<replaceable>device</replaceable> <replaceable>weight</replaceable></varname></term>
+
+        <listitem>
+          <para>Set the per-device overall block I/O weight for the executed processes, if the legacy control group
+          hierarchy is used on the system. Takes a space-separated pair of a file path and a weight value to specify
+          the device specific weight value, between 10 and 1000. (Example: "/dev/sda 500"). The file path may be
+          specified as path to a block device node or as any other file, in which case the backing block device of the
+          file system of the file is determined. This controls the <literal>blkio.weight_device</literal> control group
+          attribute, which defaults to 1000. Use this option multiple times to set weights for multiple devices. For
+          details about this control group attribute, see <ulink
+          url="https://www.kernel.org/doc/Documentation/cgroup-v1/blkio-controller.txt">blkio-controller.txt</ulink>.</para>
+
+          <para>Implies
+          <literal>BlockIOAccounting=true</literal>.</para>
+
+          <para>This setting is deprecated. Use <varname>IODeviceWeight=</varname> instead.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>BlockIOReadBandwidth=<replaceable>device</replaceable> <replaceable>bytes</replaceable></varname></term>
+        <term><varname>BlockIOWriteBandwidth=<replaceable>device</replaceable> <replaceable>bytes</replaceable></varname></term>
+
+        <listitem>
+          <para>Set the per-device overall block I/O bandwidth limit for the executed processes, if the legacy control
+          group hierarchy is used on the system. Takes a space-separated pair of a file path and a bandwidth value (in
+          bytes per second) to specify the device specific bandwidth. The file path may be a path to a block device
+          node, or as any other file in which case the backing block device of the file system of the file is used. If
+          the bandwidth is suffixed with K, M, G, or T, the specified bandwidth is parsed as Kilobytes, Megabytes,
+          Gigabytes, or Terabytes, respectively, to the base of 1000. (Example:
+          "/dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0 5M"). This controls the
+          <literal>blkio.throttle.read_bps_device</literal> and <literal>blkio.throttle.write_bps_device</literal>
+          control group attributes. Use this option multiple times to set bandwidth limits for multiple devices. For
+          details about these control group attributes, see <ulink
+          url="https://www.kernel.org/doc/Documentation/cgroup-v1/blkio-controller.txt">blkio-controller.txt</ulink>.
+          </para>
+
+          <para>Implies
+          <literal>BlockIOAccounting=true</literal>.</para>
+
+          <para>These settings are deprecated. Use <varname>IOReadBandwidthMax=</varname> and
+          <varname>IOWriteBandwidthMax=</varname> instead.</para>
+        </listitem>
+      </varlistentry>
+
+    </variablelist>
+  </refsect1>
+
+  <refsect1>
     <title>See Also</title>
     <para>
       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,