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Date: Sun, 4 Sep 2022 10:26:41 +0800
From: kernel test robot <lkp@...el.com>
To: Waiman Long <longman@...hat.com>, Tejun Heo <tj@...nel.org>,
Zefan Li <lizefan.x@...edance.com>,
Johannes Weiner <hannes@...xchg.org>,
Jonathan Corbet <corbet@....net>,
Shuah Khan <skhan@...uxfoundation.org>
Cc: kbuild-all@...ts.01.org, cgroups@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
linux-kselftest@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>,
Linux Memory Management List <linux-mm@...ck.org>,
Roman Gushchin <guro@...com>, Phil Auld <pauld@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Juri Lelli <juri.lelli@...hat.com>,
Frederic Weisbecker <frederic@...nel.org>,
Marcelo Tosatti <mtosatti@...hat.com>,
Michal Koutný <mkoutny@...e.com>,
Waiman Long <longman@...hat.com>
Subject: Re: [PATCH v12 09/10] cgroup/cpuset: Update description of
cpuset.cpus.partition in cgroup-v2.rst
Hi Waiman,
I love your patch! Perhaps something to improve:
[auto build test WARNING on linus/master]
[also build test WARNING on v6.0-rc3 next-20220901]
[cannot apply to tj-cgroup/for-next]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Waiman-Long/cgroup-cpuset-cpu-partition-code-fixes-enhancements/20220902-050019
base: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 42e66b1cc3a070671001f8a1e933a80818a192bf
reproduce:
# https://github.com/intel-lab-lkp/linux/commit/dce03e1a3eb6fce8d7c849c8daeff91ec9a47fc8
git remote add linux-review https://github.com/intel-lab-lkp/linux
git fetch --no-tags linux-review Waiman-Long/cgroup-cpuset-cpu-partition-code-fixes-enhancements/20220902-050019
git checkout dce03e1a3eb6fce8d7c849c8daeff91ec9a47fc8
make menuconfig
# enable CONFIG_COMPILE_TEST, CONFIG_WARN_MISSING_DOCUMENTS, CONFIG_WARN_ABI_ERRORS
make htmldocs
If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@...el.com>
All warnings (new ones prefixed by >>):
>> Documentation/admin-guide/cgroup-v2.rst:2191: WARNING: Malformed table.
vim +2191 Documentation/admin-guide/cgroup-v2.rst
2091
2092 cpuset.cpus
2093 A read-write multiple values file which exists on non-root
2094 cpuset-enabled cgroups.
2095
2096 It lists the requested CPUs to be used by tasks within this
2097 cgroup. The actual list of CPUs to be granted, however, is
2098 subjected to constraints imposed by its parent and can differ
2099 from the requested CPUs.
2100
2101 The CPU numbers are comma-separated numbers or ranges.
2102 For example::
2103
2104 # cat cpuset.cpus
2105 0-4,6,8-10
2106
2107 An empty value indicates that the cgroup is using the same
2108 setting as the nearest cgroup ancestor with a non-empty
2109 "cpuset.cpus" or all the available CPUs if none is found.
2110
2111 The value of "cpuset.cpus" stays constant until the next update
2112 and won't be affected by any CPU hotplug events.
2113
2114 cpuset.cpus.effective
2115 A read-only multiple values file which exists on all
2116 cpuset-enabled cgroups.
2117
2118 It lists the onlined CPUs that are actually granted to this
2119 cgroup by its parent. These CPUs are allowed to be used by
2120 tasks within the current cgroup.
2121
2122 If "cpuset.cpus" is empty, the "cpuset.cpus.effective" file shows
2123 all the CPUs from the parent cgroup that can be available to
2124 be used by this cgroup. Otherwise, it should be a subset of
2125 "cpuset.cpus" unless none of the CPUs listed in "cpuset.cpus"
2126 can be granted. In this case, it will be treated just like an
2127 empty "cpuset.cpus".
2128
2129 Its value will be affected by CPU hotplug events.
2130
2131 cpuset.mems
2132 A read-write multiple values file which exists on non-root
2133 cpuset-enabled cgroups.
2134
2135 It lists the requested memory nodes to be used by tasks within
2136 this cgroup. The actual list of memory nodes granted, however,
2137 is subjected to constraints imposed by its parent and can differ
2138 from the requested memory nodes.
2139
2140 The memory node numbers are comma-separated numbers or ranges.
2141 For example::
2142
2143 # cat cpuset.mems
2144 0-1,3
2145
2146 An empty value indicates that the cgroup is using the same
2147 setting as the nearest cgroup ancestor with a non-empty
2148 "cpuset.mems" or all the available memory nodes if none
2149 is found.
2150
2151 The value of "cpuset.mems" stays constant until the next update
2152 and won't be affected by any memory nodes hotplug events.
2153
2154 Setting a non-empty value to "cpuset.mems" causes memory of
2155 tasks within the cgroup to be migrated to the designated nodes if
2156 they are currently using memory outside of the designated nodes.
2157
2158 There is a cost for this memory migration. The migration
2159 may not be complete and some memory pages may be left behind.
2160 So it is recommended that "cpuset.mems" should be set properly
2161 before spawning new tasks into the cpuset. Even if there is
2162 a need to change "cpuset.mems" with active tasks, it shouldn't
2163 be done frequently.
2164
2165 cpuset.mems.effective
2166 A read-only multiple values file which exists on all
2167 cpuset-enabled cgroups.
2168
2169 It lists the onlined memory nodes that are actually granted to
2170 this cgroup by its parent. These memory nodes are allowed to
2171 be used by tasks within the current cgroup.
2172
2173 If "cpuset.mems" is empty, it shows all the memory nodes from the
2174 parent cgroup that will be available to be used by this cgroup.
2175 Otherwise, it should be a subset of "cpuset.mems" unless none of
2176 the memory nodes listed in "cpuset.mems" can be granted. In this
2177 case, it will be treated just like an empty "cpuset.mems".
2178
2179 Its value will be affected by memory nodes hotplug events.
2180
2181 cpuset.cpus.partition
2182 A read-write single value file which exists on non-root
2183 cpuset-enabled cgroups. This flag is owned by the parent cgroup
2184 and is not delegatable.
2185
2186 It accepts only the following input values when written to.
2187
2188 ======== ================================
2189 "member" Non-root member of a partition
2190 "root" Partition root
> 2191 "isolated" Partition root without load balancing
2192 ======== ================================
2193
2194 The root cgroup is always a partition root and its state
2195 cannot be changed. All other non-root cgroups start out as
2196 "member".
2197
2198 When set to "root", the current cgroup is the root of a new
2199 partition or scheduling domain that comprises itself and all
2200 its descendants except those that are separate partition roots
2201 themselves and their descendants.
2202
2203 When set to "isolated", the CPUs in that partition root will
2204 be in an isolated state without any load balancing from the
2205 scheduler. Tasks placed in such a partition with multiple
2206 CPUs should be carefully distributed and bound to each of the
2207 individual CPUs for optimal performance.
2208
2209 The value shown in "cpuset.cpus.effective" of a partition root
2210 is the CPUs that the partition root can dedicate to a potential
2211 new child partition root. The new child subtracts available
2212 CPUs from its parent "cpuset.cpus.effective".
2213
2214 A partition root ("root" or "isolated") can be in one of the
2215 two possible states - valid or invalid. An invalid partition
2216 root is in a degraded state where some state information may
2217 be retained, but behaves more like a "member".
2218
2219 All possible state transitions among "member", "root" and
2220 "isolated" are allowed.
2221
2222 On read, the "cpuset.cpus.partition" file can show the following
2223 values.
2224
2225 ====================== ==============================
2226 "member" Non-root member of a partition
2227 "root" Partition root
2228 "isolated" Partition root without load balancing
2229 "root invalid (<reason>)" Invalid partition root
2230 "isolated invalid (<reason>)" Invalid isolated partition root
2231 ====================== ==============================
2232
2233 In the case of an invalid partition root, a descriptive string on
2234 why the partition is invalid is included within parentheses.
2235
2236 For a partition root to become valid, the following conditions
2237 must be met.
2238
2239 1) The "cpuset.cpus" is exclusive with its siblings , i.e. they
2240 are not shared by any of its siblings (exclusivity rule).
2241 2) The parent cgroup is a valid partition root.
2242 3) The "cpuset.cpus" is not empty and must contain at least
2243 one of the CPUs from parent's "cpuset.cpus", i.e. they overlap.
2244 4) The "cpuset.cpus.effective" cannot be empty unless there is
2245 no task associated with this partition.
2246
2247 External events like hotplug or changes to "cpuset.cpus" can
2248 cause a valid partition root to become invalid and vice versa.
2249 Note that a task cannot be moved to a cgroup with empty
2250 "cpuset.cpus.effective".
2251
2252 For a valid partition root with the sibling cpu exclusivity
2253 rule enabled, changes made to "cpuset.cpus" that violate the
2254 exclusivity rule will invalidate the partition as well as its
2255 sibiling partitions with conflicting cpuset.cpus values. So
2256 care must be taking in changing "cpuset.cpus".
2257
2258 A valid non-root parent partition may distribute out all its CPUs
2259 to its child partitions when there is no task associated with it.
2260
2261 Care must be taken to change a valid partition root to
2262 "member" as all its child partitions, if present, will become
2263 invalid causing disruption to tasks running in those child
2264 partitions. These inactivated partitions could be recovered if
2265 their parent is switched back to a partition root with a proper
2266 set of "cpuset.cpus".
2267
2268 Poll and inotify events are triggered whenever the state of
2269 "cpuset.cpus.partition" changes. That includes changes caused
2270 by write to "cpuset.cpus.partition", cpu hotplug or other
2271 changes that modify the validity status of the partition.
2272 This will allow user space agents to monitor unexpected changes
2273 to "cpuset.cpus.partition" without the need to do continuous
2274 polling.
2275
2276
--
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