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authorDinakar Guniguntala <dino@in.ibm.com>2005-06-25 14:57:34 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-06-25 16:24:45 -0700
commit85d7b94981e2e919697bc235aad7367b33c3864b (patch)
tree79d7705a897abde11b5f2f967bf24487aaeea354 /Documentation
parent1a20ff27ef75d866730ee796acd811a925af762f (diff)
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[PATCH] Dynamic sched domains: cpuset changes
Adds the core update_cpu_domains code and updated cpusets documentation Signed-off-by: Dinakar Guniguntala <dino@in.ibm.com> Acked-by: Paul Jackson <pj@sgi.com> Acked-by: Nick Piggin <nickpiggin@yahoo.com.au> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/cpusets.txt16
1 files changed, 16 insertions, 0 deletions
diff --git a/Documentation/cpusets.txt b/Documentation/cpusets.txt
index 2f8f24eaefd..ad944c06031 100644
--- a/Documentation/cpusets.txt
+++ b/Documentation/cpusets.txt
@@ -51,6 +51,14 @@ mems_allowed vector.
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 cpuset that is cpu exclusive has a 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 balacing 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.
User level code may create and destroy cpusets by name in the cpuset
virtual file system, manage the attributes and permissions of these
@@ -84,6 +92,9 @@ This can be especially valuable on:
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
@@ -125,6 +136,8 @@ 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.
+ 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
@@ -136,6 +149,9 @@ 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.
+ - 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, to restrict memory to allowed nodes.