1.4 What are exclusive cpusets ?
1.5 What does notify_on_release do ?
1.6 What is memory_pressure ?
- 1.7 What is memory spread ?
- 1.8 How do I use cpusets ?
+ 1.7 How do I use cpusets ?
2. Usage Examples and Syntax
2.1 Basic Usage
2.2 Adding/removing cpus
to represent the cpuset hierarchy provides for a familiar permission
and name space for cpusets, with a minimum of additional kernel code.
-The cpus file in the root (top_cpuset) cpuset is read-only.
-It automatically tracks the value of cpu_online_map, using a CPU
-hotplug notifier. If and when memory nodes can be hotplugged,
-we expect to make the mems file in the root cpuset read-only
-as well, and have it track the value of node_online_map.
-
1.4 What are exclusive cpusets ?
--------------------------------
times 1000.
-1.7 What is memory spread ?
----------------------------
-There are two boolean flag files per cpuset that control where the
-kernel allocates pages for the file system buffers and related in
-kernel data structures. They are called 'memory_spread_page' and
-'memory_spread_slab'.
-
-If the per-cpuset boolean flag file 'memory_spread_page' is set, then
-the kernel will spread the file system buffers (page cache) evenly
-over all the nodes that the faulting task is allowed to use, instead
-of preferring to put those pages on the node where the task is running.
-
-If the per-cpuset boolean flag file 'memory_spread_slab' is set,
-then the kernel will spread some file system related slab caches,
-such as for inodes and dentries evenly over all the nodes that the
-faulting task is allowed to use, instead of preferring to put those
-pages on the node where the task is running.
-
-The setting of these flags does not affect anonymous data segment or
-stack segment pages of a task.
-
-By default, both kinds of memory spreading are off, and memory
-pages are allocated on the node local to where the task is running,
-except perhaps as modified by the tasks NUMA mempolicy or cpuset
-configuration, so long as sufficient free memory pages are available.
-
-When new cpusets are created, they inherit the memory spread settings
-of their parent.
-
-Setting memory spreading causes allocations for the affected page
-or slab caches to ignore the tasks NUMA mempolicy and be spread
-instead. Tasks using mbind() or set_mempolicy() calls to set NUMA
-mempolicies will not notice any change in these calls as a result of
-their containing tasks memory spread settings. If memory spreading
-is turned off, then the currently specified NUMA mempolicy once again
-applies to memory page allocations.
-
-Both 'memory_spread_page' and 'memory_spread_slab' are boolean flag
-files. By default they contain "0", meaning that the feature is off
-for that cpuset. If a "1" is written to that file, then that turns
-the named feature on.
-
-The implementation is simple.
-
-Setting the flag 'memory_spread_page' turns on a per-process flag
-PF_SPREAD_PAGE for each task that is in that cpuset or subsequently
-joins that cpuset. The page allocation calls for the page cache
-is modified to perform an inline check for this PF_SPREAD_PAGE task
-flag, and if set, a call to a new routine cpuset_mem_spread_node()
-returns the node to prefer for the allocation.
-
-Similarly, setting 'memory_spread_cache' turns on the flag
-PF_SPREAD_SLAB, and appropriately marked slab caches will allocate
-pages from the node returned by cpuset_mem_spread_node().
-
-The cpuset_mem_spread_node() routine is also simple. It uses the
-value of a per-task rotor cpuset_mem_spread_rotor to select the next
-node in the current tasks mems_allowed to prefer for the allocation.
-
-This memory placement policy is also known (in other contexts) as
-round-robin or interleave.
-
-This policy can provide substantial improvements for jobs that need
-to place thread local data on the corresponding node, but that need
-to access large file system data sets that need to be spread across
-the several nodes in the jobs cpuset in order to fit. Without this
-policy, especially for jobs that might have one thread reading in the
-data set, the memory allocation across the nodes in the jobs cpuset
-can become very uneven.
-
-
-1.8 How do I use cpusets ?
+1.7 How do I use cpusets ?
--------------------------
In order to minimize the impact of cpusets on critical kernel
git://git.onelab.eu / linux-2.6.git / blobdiff