diff options
Diffstat (limited to 'Documentation')
-rw-r--r-- | Documentation/scheduler/sched-design-CFS.txt | 54 | ||||
-rw-r--r-- | Documentation/scheduler/sched-rt-group.txt | 20 |
2 files changed, 7 insertions, 67 deletions
diff --git a/Documentation/scheduler/sched-design-CFS.txt b/Documentation/scheduler/sched-design-CFS.txt index 6f33593e59e2..8239ebbcddce 100644 --- a/Documentation/scheduler/sched-design-CFS.txt +++ b/Documentation/scheduler/sched-design-CFS.txt | |||
@@ -211,7 +211,7 @@ provide fair CPU time to each such task group. For example, it may be | |||
211 | desirable to first provide fair CPU time to each user on the system and then to | 211 | desirable to first provide fair CPU time to each user on the system and then to |
212 | each task belonging to a user. | 212 | each task belonging to a user. |
213 | 213 | ||
214 | CONFIG_GROUP_SCHED strives to achieve exactly that. It lets tasks to be | 214 | CONFIG_CGROUP_SCHED strives to achieve exactly that. It lets tasks to be |
215 | grouped and divides CPU time fairly among such groups. | 215 | grouped and divides CPU time fairly among such groups. |
216 | 216 | ||
217 | CONFIG_RT_GROUP_SCHED permits to group real-time (i.e., SCHED_FIFO and | 217 | CONFIG_RT_GROUP_SCHED permits to group real-time (i.e., SCHED_FIFO and |
@@ -220,38 +220,11 @@ SCHED_RR) tasks. | |||
220 | CONFIG_FAIR_GROUP_SCHED permits to group CFS (i.e., SCHED_NORMAL and | 220 | CONFIG_FAIR_GROUP_SCHED permits to group CFS (i.e., SCHED_NORMAL and |
221 | SCHED_BATCH) tasks. | 221 | SCHED_BATCH) tasks. |
222 | 222 | ||
223 | At present, there are two (mutually exclusive) mechanisms to group tasks for | 223 | These options need CONFIG_CGROUPS to be defined, and let the administrator |
224 | CPU bandwidth control purposes: | ||
225 | |||
226 | - Based on user id (CONFIG_USER_SCHED) | ||
227 | |||
228 | With this option, tasks are grouped according to their user id. | ||
229 | |||
230 | - Based on "cgroup" pseudo filesystem (CONFIG_CGROUP_SCHED) | ||
231 | |||
232 | This options needs CONFIG_CGROUPS to be defined, and lets the administrator | ||
233 | create arbitrary groups of tasks, using the "cgroup" pseudo filesystem. See | 224 | create arbitrary groups of tasks, using the "cgroup" pseudo filesystem. See |
234 | Documentation/cgroups/cgroups.txt for more information about this filesystem. | 225 | Documentation/cgroups/cgroups.txt for more information about this filesystem. |
235 | 226 | ||
236 | Only one of these options to group tasks can be chosen and not both. | 227 | When CONFIG_FAIR_GROUP_SCHED is defined, a "cpu.shares" file is created for each |
237 | |||
238 | When CONFIG_USER_SCHED is defined, a directory is created in sysfs for each new | ||
239 | user and a "cpu_share" file is added in that directory. | ||
240 | |||
241 | # cd /sys/kernel/uids | ||
242 | # cat 512/cpu_share # Display user 512's CPU share | ||
243 | 1024 | ||
244 | # echo 2048 > 512/cpu_share # Modify user 512's CPU share | ||
245 | # cat 512/cpu_share # Display user 512's CPU share | ||
246 | 2048 | ||
247 | # | ||
248 | |||
249 | CPU bandwidth between two users is divided in the ratio of their CPU shares. | ||
250 | For example: if you would like user "root" to get twice the bandwidth of user | ||
251 | "guest," then set the cpu_share for both the users such that "root"'s cpu_share | ||
252 | is twice "guest"'s cpu_share. | ||
253 | |||
254 | When CONFIG_CGROUP_SCHED is defined, a "cpu.shares" file is created for each | ||
255 | group created using the pseudo filesystem. See example steps below to create | 228 | group created using the pseudo filesystem. See example steps below to create |
256 | task groups and modify their CPU share using the "cgroups" pseudo filesystem. | 229 | task groups and modify their CPU share using the "cgroups" pseudo filesystem. |
257 | 230 | ||
@@ -273,24 +246,3 @@ task groups and modify their CPU share using the "cgroups" pseudo filesystem. | |||
273 | 246 | ||
274 | # #Launch gmplayer (or your favourite movie player) | 247 | # #Launch gmplayer (or your favourite movie player) |
275 | # echo <movie_player_pid> > multimedia/tasks | 248 | # echo <movie_player_pid> > multimedia/tasks |
276 | |||
277 | 8. Implementation note: user namespaces | ||
278 | |||
279 | User namespaces are intended to be hierarchical. But they are currently | ||
280 | only partially implemented. Each of those has ramifications for CFS. | ||
281 | |||
282 | First, since user namespaces are hierarchical, the /sys/kernel/uids | ||
283 | presentation is inadequate. Eventually we will likely want to use sysfs | ||
284 | tagging to provide private views of /sys/kernel/uids within each user | ||
285 | namespace. | ||
286 | |||
287 | Second, the hierarchical nature is intended to support completely | ||
288 | unprivileged use of user namespaces. So if using user groups, then | ||
289 | we want the users in a user namespace to be children of the user | ||
290 | who created it. | ||
291 | |||
292 | That is currently unimplemented. So instead, every user in a new | ||
293 | user namespace will receive 1024 shares just like any user in the | ||
294 | initial user namespace. Note that at the moment creation of a new | ||
295 | user namespace requires each of CAP_SYS_ADMIN, CAP_SETUID, and | ||
296 | CAP_SETGID. | ||
diff --git a/Documentation/scheduler/sched-rt-group.txt b/Documentation/scheduler/sched-rt-group.txt index 86eabe6c3419..605b0d40329d 100644 --- a/Documentation/scheduler/sched-rt-group.txt +++ b/Documentation/scheduler/sched-rt-group.txt | |||
@@ -126,23 +126,12 @@ priority! | |||
126 | 2.3 Basis for grouping tasks | 126 | 2.3 Basis for grouping tasks |
127 | ---------------------------- | 127 | ---------------------------- |
128 | 128 | ||
129 | There are two compile-time settings for allocating CPU bandwidth. These are | 129 | Enabling CONFIG_RT_GROUP_SCHED lets you explicitly allocate real |
130 | configured using the "Basis for grouping tasks" multiple choice menu under | 130 | CPU bandwidth to task groups. |
131 | General setup > Group CPU Scheduler: | ||
132 | |||
133 | a. CONFIG_USER_SCHED (aka "Basis for grouping tasks" = "user id") | ||
134 | |||
135 | This lets you use the virtual files under | ||
136 | "/sys/kernel/uids/<uid>/cpu_rt_runtime_us" to control he CPU time reserved for | ||
137 | each user . | ||
138 | |||
139 | The other option is: | ||
140 | |||
141 | .o CONFIG_CGROUP_SCHED (aka "Basis for grouping tasks" = "Control groups") | ||
142 | 131 | ||
143 | This uses the /cgroup virtual file system and | 132 | This uses the /cgroup virtual file system and |
144 | "/cgroup/<cgroup>/cpu.rt_runtime_us" to control the CPU time reserved for each | 133 | "/cgroup/<cgroup>/cpu.rt_runtime_us" to control the CPU time reserved for each |
145 | control group instead. | 134 | control group. |
146 | 135 | ||
147 | For more information on working with control groups, you should read | 136 | For more information on working with control groups, you should read |
148 | Documentation/cgroups/cgroups.txt as well. | 137 | Documentation/cgroups/cgroups.txt as well. |
@@ -161,8 +150,7 @@ For now, this can be simplified to just the following (but see Future plans): | |||
161 | =============== | 150 | =============== |
162 | 151 | ||
163 | There is work in progress to make the scheduling period for each group | 152 | There is work in progress to make the scheduling period for each group |
164 | ("/sys/kernel/uids/<uid>/cpu_rt_period_us" or | 153 | ("/cgroup/<cgroup>/cpu.rt_period_us") configurable as well. |
165 | "/cgroup/<cgroup>/cpu.rt_period_us" respectively) configurable as well. | ||
166 | 154 | ||
167 | The constraint on the period is that a subgroup must have a smaller or | 155 | The constraint on the period is that a subgroup must have a smaller or |
168 | equal period to its parent. But realistically its not very useful _yet_ | 156 | equal period to its parent. But realistically its not very useful _yet_ |