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| author | Dinakar Guniguntala <dino@in.ibm.com> | 2005-06-25 14:57:34 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-06-25 16:24:45 -0700 |
| commit | 85d7b94981e2e919697bc235aad7367b33c3864b (patch) | |
| tree | 79d7705a897abde11b5f2f967bf24487aaeea354 /Documentation/cpusets.txt | |
| parent | 1a20ff27ef75d866730ee796acd811a925af762f (diff) | |
| download | lwn-85d7b94981e2e919697bc235aad7367b33c3864b.tar.gz lwn-85d7b94981e2e919697bc235aad7367b33c3864b.zip | |
[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/cpusets.txt')
| -rw-r--r-- | Documentation/cpusets.txt | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/Documentation/cpusets.txt b/Documentation/cpusets.txt index 2f8f24eaefd9..ad944c060312 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. |