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doc: cpuset: Update the cpuset flag file
This patch is for modifying with correct cuset flag file. We need to update current manual for cpuset. For example, before) cpus, cpu_exclusive, mems after ) cpuset.cpus, cpuset.cpu_exclusive, cpuset.mems Signed-off-by: Geunsik Lim <geunsik.lim@samsung.com> Acked-by: Paul Menage <menage@google.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
This commit is contained in:
GeunSik Lim
Jiri Kosina
parent
586f64c749
commit
e21a05cb40
@ -168,20 +168,20 @@ Each cpuset is represented by a directory in the cgroup file system
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containing (on top of the standard cgroup files) the following
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files describing that cpuset:
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- cpus: list of CPUs in that cpuset
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- mems: list of Memory Nodes in that cpuset
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- memory_migrate flag: if set, move pages to cpusets nodes
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- cpu_exclusive flag: is cpu placement exclusive?
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- mem_exclusive flag: is memory placement exclusive?
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- mem_hardwall flag: is memory allocation hardwalled
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- memory_pressure: measure of how much paging pressure in cpuset
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- memory_spread_page flag: if set, spread page cache evenly on allowed nodes
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- memory_spread_slab flag: if set, spread slab cache evenly on allowed nodes
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- sched_load_balance flag: if set, load balance within CPUs on that cpuset
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- sched_relax_domain_level: the searching range when migrating tasks
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- cpuset.cpus: list of CPUs in that cpuset
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- cpuset.mems: list of Memory Nodes in that cpuset
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- cpuset.memory_migrate flag: if set, move pages to cpusets nodes
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- cpuset.cpu_exclusive flag: is cpu placement exclusive?
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- cpuset.mem_exclusive flag: is memory placement exclusive?
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- cpuset.mem_hardwall flag: is memory allocation hardwalled
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- cpuset.memory_pressure: measure of how much paging pressure in cpuset
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- cpuset.memory_spread_page flag: if set, spread page cache evenly on allowed nodes
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- cpuset.memory_spread_slab flag: if set, spread slab cache evenly on allowed nodes
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- cpuset.sched_load_balance flag: if set, load balance within CPUs on that cpuset
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- cpuset.sched_relax_domain_level: the searching range when migrating tasks
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In addition, the root cpuset only has the following file:
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- memory_pressure_enabled flag: compute memory_pressure?
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- cpuset.memory_pressure_enabled flag: compute memory_pressure?
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New cpusets are created using the mkdir system call or shell
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command. The properties of a cpuset, such as its flags, allowed
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@ -229,7 +229,7 @@ If a cpuset is cpu or mem exclusive, no other cpuset, other than
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a direct ancestor or descendant, may share any of the same CPUs or
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Memory Nodes.
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A cpuset that is mem_exclusive *or* mem_hardwall is "hardwalled",
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A cpuset that is cpuset.mem_exclusive *or* cpuset.mem_hardwall is "hardwalled",
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i.e. it restricts kernel allocations for page, buffer and other data
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commonly shared by the kernel across multiple users. All cpusets,
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whether hardwalled or not, restrict allocations of memory for user
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@ -304,15 +304,15 @@ times 1000.
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---------------------------
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There are two boolean flag files per cpuset that control where the
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kernel allocates pages for the file system buffers and related in
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kernel data structures. They are called 'memory_spread_page' and
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'memory_spread_slab'.
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kernel data structures. They are called 'cpuset.memory_spread_page' and
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'cpuset.memory_spread_slab'.
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If the per-cpuset boolean flag file 'memory_spread_page' is set, then
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If the per-cpuset boolean flag file 'cpuset.memory_spread_page' is set, then
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the kernel will spread the file system buffers (page cache) evenly
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over all the nodes that the faulting task is allowed to use, instead
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of preferring to put those pages on the node where the task is running.
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If the per-cpuset boolean flag file 'memory_spread_slab' is set,
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If the per-cpuset boolean flag file 'cpuset.memory_spread_slab' is set,
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then the kernel will spread some file system related slab caches,
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such as for inodes and dentries evenly over all the nodes that the
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faulting task is allowed to use, instead of preferring to put those
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@ -337,21 +337,21 @@ their containing tasks memory spread settings. If memory spreading
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is turned off, then the currently specified NUMA mempolicy once again
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applies to memory page allocations.
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Both 'memory_spread_page' and 'memory_spread_slab' are boolean flag
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Both 'cpuset.memory_spread_page' and 'cpuset.memory_spread_slab' are boolean flag
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files. By default they contain "0", meaning that the feature is off
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for that cpuset. If a "1" is written to that file, then that turns
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the named feature on.
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The implementation is simple.
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Setting the flag 'memory_spread_page' turns on a per-process flag
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Setting the flag 'cpuset.memory_spread_page' turns on a per-process flag
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PF_SPREAD_PAGE for each task that is in that cpuset or subsequently
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joins that cpuset. The page allocation calls for the page cache
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is modified to perform an inline check for this PF_SPREAD_PAGE task
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flag, and if set, a call to a new routine cpuset_mem_spread_node()
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returns the node to prefer for the allocation.
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Similarly, setting 'memory_spread_slab' turns on the flag
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Similarly, setting 'cpuset.memory_spread_slab' turns on the flag
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PF_SPREAD_SLAB, and appropriately marked slab caches will allocate
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pages from the node returned by cpuset_mem_spread_node().
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@ -404,24 +404,24 @@ the following two situations:
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system overhead on those CPUs, including avoiding task load
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balancing if that is not needed.
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When the per-cpuset flag "sched_load_balance" is enabled (the default
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setting), it requests that all the CPUs in that cpusets allowed 'cpus'
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When the per-cpuset flag "cpuset.sched_load_balance" is enabled (the default
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setting), it requests that all the CPUs in that cpusets allowed 'cpuset.cpus'
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be contained in a single sched domain, ensuring that load balancing
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can move a task (not otherwised pinned, as by sched_setaffinity)
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from any CPU in that cpuset to any other.
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When the per-cpuset flag "sched_load_balance" is disabled, then the
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When the per-cpuset flag "cpuset.sched_load_balance" is disabled, then the
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scheduler will avoid load balancing across the CPUs in that cpuset,
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--except-- in so far as is necessary because some overlapping cpuset
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has "sched_load_balance" enabled.
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So, for example, if the top cpuset has the flag "sched_load_balance"
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So, for example, if the top cpuset has the flag "cpuset.sched_load_balance"
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enabled, then the scheduler will have one sched domain covering all
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CPUs, and the setting of the "sched_load_balance" flag in any other
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CPUs, and the setting of the "cpuset.sched_load_balance" flag in any other
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cpusets won't matter, as we're already fully load balancing.
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Therefore in the above two situations, the top cpuset flag
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"sched_load_balance" should be disabled, and only some of the smaller,
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"cpuset.sched_load_balance" should be disabled, and only some of the smaller,
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child cpusets have this flag enabled.
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When doing this, you don't usually want to leave any unpinned tasks in
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@ -433,7 +433,7 @@ scheduler might not consider the possibility of load balancing that
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task to that underused CPU.
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Of course, tasks pinned to a particular CPU can be left in a cpuset
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that disables "sched_load_balance" as those tasks aren't going anywhere
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that disables "cpuset.sched_load_balance" as those tasks aren't going anywhere
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else anyway.
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There is an impedance mismatch here, between cpusets and sched domains.
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@ -443,19 +443,19 @@ overlap and each CPU is in at most one sched domain.
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It is necessary for sched domains to be flat because load balancing
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across partially overlapping sets of CPUs would risk unstable dynamics
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that would be beyond our understanding. So if each of two partially
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overlapping cpusets enables the flag 'sched_load_balance', then we
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overlapping cpusets enables the flag 'cpuset.sched_load_balance', then we
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form a single sched domain that is a superset of both. We won't move
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a task to a CPU outside it cpuset, but the scheduler load balancing
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code might waste some compute cycles considering that possibility.
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This mismatch is why there is not a simple one-to-one relation
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between which cpusets have the flag "sched_load_balance" enabled,
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between which cpusets have the flag "cpuset.sched_load_balance" enabled,
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and the sched domain configuration. If a cpuset enables the flag, it
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will get balancing across all its CPUs, but if it disables the flag,
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it will only be assured of no load balancing if no other overlapping
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cpuset enables the flag.
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If two cpusets have partially overlapping 'cpus' allowed, and only
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If two cpusets have partially overlapping 'cpuset.cpus' allowed, and only
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one of them has this flag enabled, then the other may find its
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tasks only partially load balanced, just on the overlapping CPUs.
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This is just the general case of the top_cpuset example given a few
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@ -468,23 +468,23 @@ load balancing to the other CPUs.
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1.7.1 sched_load_balance implementation details.
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------------------------------------------------
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The per-cpuset flag 'sched_load_balance' defaults to enabled (contrary
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The per-cpuset flag 'cpuset.sched_load_balance' defaults to enabled (contrary
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to most cpuset flags.) When enabled for a cpuset, the kernel will
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ensure that it can load balance across all the CPUs in that cpuset
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(makes sure that all the CPUs in the cpus_allowed of that cpuset are
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in the same sched domain.)
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If two overlapping cpusets both have 'sched_load_balance' enabled,
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If two overlapping cpusets both have 'cpuset.sched_load_balance' enabled,
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then they will be (must be) both in the same sched domain.
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If, as is the default, the top cpuset has 'sched_load_balance' enabled,
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If, as is the default, the top cpuset has 'cpuset.sched_load_balance' enabled,
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then by the above that means there is a single sched domain covering
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the whole system, regardless of any other cpuset settings.
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The kernel commits to user space that it will avoid load balancing
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where it can. It will pick as fine a granularity partition of sched
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domains as it can while still providing load balancing for any set
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of CPUs allowed to a cpuset having 'sched_load_balance' enabled.
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of CPUs allowed to a cpuset having 'cpuset.sched_load_balance' enabled.
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The internal kernel cpuset to scheduler interface passes from the
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cpuset code to the scheduler code a partition of the load balanced
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@ -495,9 +495,9 @@ all the CPUs that must be load balanced.
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The cpuset code builds a new such partition and passes it to the
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scheduler sched domain setup code, to have the sched domains rebuilt
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as necessary, whenever:
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- the 'sched_load_balance' flag of a cpuset with non-empty CPUs changes,
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- the 'cpuset.sched_load_balance' flag of a cpuset with non-empty CPUs changes,
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- or CPUs come or go from a cpuset with this flag enabled,
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- or 'sched_relax_domain_level' value of a cpuset with non-empty CPUs
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- or 'cpuset.sched_relax_domain_level' value of a cpuset with non-empty CPUs
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and with this flag enabled changes,
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- or a cpuset with non-empty CPUs and with this flag enabled is removed,
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- or a cpu is offlined/onlined.
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@ -542,7 +542,7 @@ As the result, task B on CPU X need to wait task A or wait load balance
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on the next tick. For some applications in special situation, waiting
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1 tick may be too long.
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The 'sched_relax_domain_level' file allows you to request changing
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The 'cpuset.sched_relax_domain_level' file allows you to request changing
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this searching range as you like. This file takes int value which
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indicates size of searching range in levels ideally as follows,
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otherwise initial value -1 that indicates the cpuset has no request.
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@ -559,8 +559,8 @@ The system default is architecture dependent. The system default
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can be changed using the relax_domain_level= boot parameter.
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This file is per-cpuset and affect the sched domain where the cpuset
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belongs to. Therefore if the flag 'sched_load_balance' of a cpuset
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is disabled, then 'sched_relax_domain_level' have no effect since
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belongs to. Therefore if the flag 'cpuset.sched_load_balance' of a cpuset
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is disabled, then 'cpuset.sched_relax_domain_level' have no effect since
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there is no sched domain belonging the cpuset.
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If multiple cpusets are overlapping and hence they form a single sched
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@ -607,9 +607,9 @@ from one cpuset to another, then the kernel will adjust the tasks
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memory placement, as above, the next time that the kernel attempts
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to allocate a page of memory for that task.
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If a cpuset has its 'cpus' modified, then each task in that cpuset
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If a cpuset has its 'cpuset.cpus' modified, then each task in that cpuset
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will have its allowed CPU placement changed immediately. Similarly,
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if a tasks pid is written to another cpusets 'tasks' file, then its
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if a tasks pid is written to another cpusets 'cpuset.tasks' file, then its
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allowed CPU placement is changed immediately. If such a task had been
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bound to some subset of its cpuset using the sched_setaffinity() call,
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the task will be allowed to run on any CPU allowed in its new cpuset,
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@ -622,8 +622,8 @@ and the processor placement is updated immediately.
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Normally, once a page is allocated (given a physical page
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of main memory) then that page stays on whatever node it
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was allocated, so long as it remains allocated, even if the
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cpusets memory placement policy 'mems' subsequently changes.
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If the cpuset flag file 'memory_migrate' is set true, then when
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cpusets memory placement policy 'cpuset.mems' subsequently changes.
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If the cpuset flag file 'cpuset.memory_migrate' is set true, then when
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tasks are attached to that cpuset, any pages that task had
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allocated to it on nodes in its previous cpuset are migrated
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to the tasks new cpuset. The relative placement of the page within
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@ -631,12 +631,12 @@ the cpuset is preserved during these migration operations if possible.
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For example if the page was on the second valid node of the prior cpuset
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then the page will be placed on the second valid node of the new cpuset.
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Also if 'memory_migrate' is set true, then if that cpusets
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'mems' file is modified, pages allocated to tasks in that
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cpuset, that were on nodes in the previous setting of 'mems',
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Also if 'cpuset.memory_migrate' is set true, then if that cpusets
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'cpuset.mems' file is modified, pages allocated to tasks in that
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cpuset, that were on nodes in the previous setting of 'cpuset.mems',
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will be moved to nodes in the new setting of 'mems.'
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Pages that were not in the tasks prior cpuset, or in the cpusets
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prior 'mems' setting, will not be moved.
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prior 'cpuset.mems' setting, will not be moved.
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There is an exception to the above. If hotplug functionality is used
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to remove all the CPUs that are currently assigned to a cpuset,
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@ -678,8 +678,8 @@ and then start a subshell 'sh' in that cpuset:
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cd /dev/cpuset
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mkdir Charlie
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cd Charlie
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/bin/echo 2-3 > cpus
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/bin/echo 1 > mems
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/bin/echo 2-3 > cpuset.cpus
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/bin/echo 1 > cpuset.mems
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/bin/echo $$ > tasks
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sh
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# The subshell 'sh' is now running in cpuset Charlie
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@ -725,10 +725,13 @@ Now you want to do something with this cpuset.
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In this directory you can find several files:
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# ls
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cpu_exclusive memory_migrate mems tasks
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cpus memory_pressure notify_on_release
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mem_exclusive memory_spread_page sched_load_balance
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mem_hardwall memory_spread_slab sched_relax_domain_level
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cpuset.cpu_exclusive cpuset.memory_spread_slab
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cpuset.cpus cpuset.mems
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cpuset.mem_exclusive cpuset.sched_load_balance
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cpuset.mem_hardwall cpuset.sched_relax_domain_level
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cpuset.memory_migrate notify_on_release
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cpuset.memory_pressure tasks
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cpuset.memory_spread_page
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Reading them will give you information about the state of this cpuset:
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the CPUs and Memory Nodes it can use, the processes that are using
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@ -736,13 +739,13 @@ it, its properties. By writing to these files you can manipulate
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the cpuset.
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Set some flags:
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# /bin/echo 1 > cpu_exclusive
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# /bin/echo 1 > cpuset.cpu_exclusive
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Add some cpus:
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# /bin/echo 0-7 > cpus
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# /bin/echo 0-7 > cpuset.cpus
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Add some mems:
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# /bin/echo 0-7 > mems
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# /bin/echo 0-7 > cpuset.mems
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Now attach your shell to this cpuset:
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# /bin/echo $$ > tasks
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@ -774,28 +777,28 @@ echo "/sbin/cpuset_release_agent" > /dev/cpuset/release_agent
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This is the syntax to use when writing in the cpus or mems files
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in cpuset directories:
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# /bin/echo 1-4 > cpus -> set cpus list to cpus 1,2,3,4
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# /bin/echo 1,2,3,4 > cpus -> set cpus list to cpus 1,2,3,4
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# /bin/echo 1-4 > cpuset.cpus -> set cpus list to cpus 1,2,3,4
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# /bin/echo 1,2,3,4 > cpuset.cpus -> set cpus list to cpus 1,2,3,4
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To add a CPU to a cpuset, write the new list of CPUs including the
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CPU to be added. To add 6 to the above cpuset:
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# /bin/echo 1-4,6 > cpus -> set cpus list to cpus 1,2,3,4,6
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# /bin/echo 1-4,6 > cpuset.cpus -> set cpus list to cpus 1,2,3,4,6
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Similarly to remove a CPU from a cpuset, write the new list of CPUs
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without the CPU to be removed.
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To remove all the CPUs:
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# /bin/echo "" > cpus -> clear cpus list
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# /bin/echo "" > cpuset.cpus -> clear cpus list
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2.3 Setting flags
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-----------------
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The syntax is very simple:
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# /bin/echo 1 > cpu_exclusive -> set flag 'cpu_exclusive'
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# /bin/echo 0 > cpu_exclusive -> unset flag 'cpu_exclusive'
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# /bin/echo 1 > cpuset.cpu_exclusive -> set flag 'cpuset.cpu_exclusive'
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# /bin/echo 0 > cpuset.cpu_exclusive -> unset flag 'cpuset.cpu_exclusive'
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2.4 Attaching processes
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-----------------------
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