include/linux/sched/sd_flags.h

Source file repositories/reference/linux-study-clean/include/linux/sched/sd_flags.h

File Facts

System
Linux kernel
Corpus path
include/linux/sched/sd_flags.h
Extension
.h
Size
5200 bytes
Lines
163
Domain
Core OS
Bucket
Core Kernel Interface
Inferred role
Core OS: implementation source
Status
source implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

Dependency Surface

Detected Declarations

Annotated Snippet

#ifndef SD_FLAG
# error "Incorrect import of SD flags definitions"
#endif

/*
 * Hierarchical metaflags
 *
 * SHARED_CHILD: These flags are meant to be set from the base domain upwards.
 * If a domain has this flag set, all of its children should have it set. This
 * is usually because the flag describes some shared resource (all CPUs in that
 * domain share the same resource), or because they are tied to a scheduling
 * behaviour that we want to disable at some point in the hierarchy for
 * scalability reasons.
 *
 * In those cases it doesn't make sense to have the flag set for a domain but
 * not have it in (some of) its children: sched domains ALWAYS span their child
 * domains, so operations done with parent domains will cover CPUs in the lower
 * child domains.
 *
 *
 * SHARED_PARENT: These flags are meant to be set from the highest domain
 * downwards. If a domain has this flag set, all of its parents should have it
 * set. This is usually for topology properties that start to appear above a
 * certain level (e.g. domain starts spanning CPUs outside of the base CPU's
 * socket).
 */
#define SDF_SHARED_CHILD       0x1
#define SDF_SHARED_PARENT      0x2

/*
 * Behavioural metaflags
 *
 * NEEDS_GROUPS: These flags are only relevant if the domain they are set on has
 * more than one group. This is usually for balancing flags (load balancing
 * involves equalizing a metric between groups), or for flags describing some
 * shared resource (which would be shared between groups).
 */
#define SDF_NEEDS_GROUPS       0x4

/*
 * Balance when about to become idle
 *
 * SHARED_CHILD: Set from the base domain up to cpuset.sched_relax_domain_level.
 * NEEDS_GROUPS: Load balancing flag.
 */
SD_FLAG(SD_BALANCE_NEWIDLE, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS)

/*
 * Balance on exec
 *
 * SHARED_CHILD: Set from the base domain up to the NUMA reclaim level.
 * NEEDS_GROUPS: Load balancing flag.
 */
SD_FLAG(SD_BALANCE_EXEC, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS)

/*
 * Balance on fork, clone
 *
 * SHARED_CHILD: Set from the base domain up to the NUMA reclaim level.
 * NEEDS_GROUPS: Load balancing flag.
 */
SD_FLAG(SD_BALANCE_FORK, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS)

/*
 * Balance on wakeup
 *
 * SHARED_CHILD: Set from the base domain up to cpuset.sched_relax_domain_level.
 * NEEDS_GROUPS: Load balancing flag.
 */
SD_FLAG(SD_BALANCE_WAKE, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS)

/*
 * Consider waking task on waking CPU.
 *
 * SHARED_CHILD: Set from the base domain up to the NUMA reclaim level.
 */
SD_FLAG(SD_WAKE_AFFINE, SDF_SHARED_CHILD)

/*
 * Domain members have different CPU capacities
 *
 * SHARED_PARENT: Set from the topmost domain down to the first domain where
 *                asymmetry is detected.
 * NEEDS_GROUPS: Per-CPU capacity is asymmetric between groups.
 */
SD_FLAG(SD_ASYM_CPUCAPACITY, SDF_SHARED_PARENT | SDF_NEEDS_GROUPS)

/*
 * Domain members have different CPU capacities spanning all unique CPU
 * capacity values.

Annotation

Implementation Notes