Merge branch 'fixes-2.6.24' of master.kernel.org:/pub/scm/linux/kernel/git/galak...

[karo-tx-linux.git] / Documentation / cpusets.txt

diff --git a/Documentation/cpusets.txt b/Documentation/cpusets.txt
index 842f0d1ab2165781420fdd53b3875a16ba91adb6..ec9de6917f01f34c088cd612121caaadc3edf08b 100644 (file)
--- a/Documentation/cpusets.txt
+++ b/Documentation/cpusets.txt
@@ -35,7 +35,8 @@ CONTENTS:
 ----------------------
 
 Cpusets provide a mechanism for assigning a set of CPUs and Memory
 ----------------------
 
 Cpusets provide a mechanism for assigning a set of CPUs and Memory

-Nodes to a set of tasks.
+Nodes to a set of tasks.   In this document "Memory Node" refers to
+an on-line node that contains memory.

 
 Cpusets constrain the CPU and Memory placement of tasks to only
 the resources within a tasks current cpuset.  They form a nested
 
 Cpusets constrain the CPU and Memory placement of tasks to only
 the resources within a tasks current cpuset.  They form a nested


@@ -86,9 +87,6 @@ This can be especially valuable on:
       and a database), or
     * NUMA systems running large HPC applications with demanding
       performance characteristics.
       and a database), or
     * NUMA systems running large HPC applications with demanding
       performance characteristics.

-    * Also cpu_exclusive cpusets are useful for servers running orthogonal
-      workloads such as RT applications requiring low latency and HPC
-      applications that are throughput sensitive

 
 These subsets, or "soft partitions" must be able to be dynamically
 adjusted, as the job mix changes, without impacting other concurrently
 
 These subsets, or "soft partitions" must be able to be dynamically
 adjusted, as the job mix changes, without impacting other concurrently


@@ -131,8 +129,6 @@ Cpusets extends these two mechanisms as follows:
  - A cpuset may be marked exclusive, which ensures that no other
    cpuset (except direct ancestors and descendents) may contain
    any overlapping CPUs or Memory Nodes.
  - A cpuset may be marked exclusive, which ensures that no other
    cpuset (except direct ancestors and descendents) may contain
    any overlapping CPUs or Memory Nodes.

-   Also a cpu_exclusive cpuset would be associated with a sched
-   domain.

  - You can list all the tasks (by pid) attached to any cpuset.
 
 The implementation of cpusets requires a few, simple hooks
  - You can list all the tasks (by pid) attached to any cpuset.
 
 The implementation of cpusets requires a few, simple hooks


@@ -144,9 +140,6 @@ into the rest of the kernel, none in performance critical paths:
    allowed in that tasks cpuset.
  - in sched.c migrate_all_tasks(), to keep migrating tasks within
    the CPUs allowed by their cpuset, if possible.
    allowed in that tasks cpuset.
  - in sched.c migrate_all_tasks(), to keep migrating tasks within
    the CPUs allowed by their cpuset, if possible.

- - in sched.c, a new API partition_sched_domains for handling
-   sched domain changes associated with cpu_exclusive cpusets
-   and related changes in both sched.c and arch/ia64/kernel/domain.c

  - in the mbind and set_mempolicy system calls, to mask the requested
    Memory Nodes by what's allowed in that tasks cpuset.
  - in page_alloc.c, to restrict memory to allowed nodes.
  - in the mbind and set_mempolicy system calls, to mask the requested
    Memory Nodes by what's allowed in that tasks cpuset.
  - in page_alloc.c, to restrict memory to allowed nodes.


@@ -220,8 +213,8 @@ and name space for cpusets, with a minimum of additional kernel code.
 The cpus and mems files in the root (top_cpuset) cpuset are
 read-only.  The cpus file automatically tracks the value of
 cpu_online_map using a CPU hotplug notifier, and the mems file
 The cpus and mems files in the root (top_cpuset) cpuset are
 read-only.  The cpus file automatically tracks the value of
 cpu_online_map using a CPU hotplug notifier, and the mems file

-automatically tracks the value of node_online_map using the
-cpuset_track_online_nodes() hook.
+automatically tracks the value of node_states[N_MEMORY]--i.e.,
+nodes with memory--using the cpuset_track_online_nodes() hook.

 
 
 1.4 What are exclusive cpusets ?
 
 
 1.4 What are exclusive cpusets ?


@@ -231,15 +224,6 @@ If a cpuset is cpu or mem exclusive, no other cpuset, other than
 a direct ancestor or descendent, may share any of the same CPUs or
 Memory Nodes.
 
 a direct ancestor or descendent, may share any of the same CPUs or
 Memory Nodes.
 

-A cpuset that is cpu_exclusive has a scheduler (sched) domain
-associated with it.  The sched domain consists of all CPUs in the
-current cpuset that are not part of any exclusive child cpusets.
-This ensures that the scheduler load balancing code only balances
-against the CPUs that are in the sched domain as defined above and
-not all of the CPUs in the system. This removes any overhead due to
-load balancing code trying to pull tasks outside of the cpu_exclusive
-cpuset only to be prevented by the tasks' cpus_allowed mask.
-

 A cpuset that is mem_exclusive restricts kernel allocations for
 page, buffer and other data commonly shared by the kernel across
 multiple users.  All cpusets, whether mem_exclusive or not, restrict
 A cpuset that is mem_exclusive restricts kernel allocations for
 page, buffer and other data commonly shared by the kernel across
 multiple users.  All cpusets, whether mem_exclusive or not, restrict


@@ -557,6 +541,9 @@ Set some flags:
 Add some cpus:
 # /bin/echo 0-7 > cpus
 
 Add some cpus:
 # /bin/echo 0-7 > cpus
 

+Add some mems:
+# /bin/echo 0-7 > mems
+

 Now attach your shell to this cpuset:
 # /bin/echo $$ > tasks
 
 Now attach your shell to this cpuset:
 # /bin/echo $$ > tasks