GitHub-Mirror/Star64_linux
2
0
Fork 0
mirror of https://github.com/Fishwaldo/Star64_linux.git synced 2025-06-23 07:01:23 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions

sched/core: Distribute tasks within affinity masks

Browse source 
Currently, when updating the affinity of tasks via either cpusets.cpus,
or, sched_setaffinity(); tasks not currently running within the newly
specified mask will be arbitrarily assigned to the first CPU within the
mask.

This (particularly in the case that we are restricting masks) can
result in many tasks being assigned to the first CPUs of their new
masks.

This:
 1) Can induce scheduling delays while the load-balancer has a chance to
    spread them between their new CPUs.
 2) Can antogonize a poor load-balancer behavior where it has a
    difficult time recognizing that a cross-socket imbalance has been
    forced by an affinity mask.

This change adds a new cpumask interface to allow iterated calls to
distribute within the intersection of the provided masks.

The cases that this mainly affects are:
 - modifying cpuset.cpus
 - when tasks join a cpuset
 - when modifying a task's affinity via sched_setaffinity(2)

Signed-off-by: Paul Turner <pjt@google.com>
Signed-off-by: Josh Don <joshdon@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Qais Yousef <qais.yousef@arm.com>
Tested-by: Qais Yousef <qais.yousef@arm.com>
Link: https://lkml.kernel.org/r/20200311010113.136465-1-joshdon@google.com
This commit is contained in:
Paul Turner 2020-03-10 18:01:13 -07:00 • committed by Peter Zijlstra
parent fe61468b2c
commit 46a87b3851
3 changed files with 42 additions and 1 deletions
Download patch file Download diff file Expand all files Collapse all files

7
include/linux/cpumask.h
View file

@ -194,6 +194,11 @@ static inline unsigned int cpumask_local_spread(unsigned int i, int node)
return 0;
}
static inline int cpumask_any_and_distribute(const struct cpumask *src1p,
const struct cpumask *src2p) {
return cpumask_next_and(-1, src1p, src2p);
}
#define for_each_cpu(cpu, mask) \
for ((cpu) = 0; (cpu) < 1; (cpu)++, (void)mask)
#define for_each_cpu_not(cpu, mask) \
@ -245,6 +250,8 @@ static inline unsigned int cpumask_next_zero(int n, const struct cpumask *srcp)
int cpumask_next_and(int n, const struct cpumask *, const struct cpumask *);
int cpumask_any_but(const struct cpumask *mask, unsigned int cpu);
unsigned int cpumask_local_spread(unsigned int i, int node);
int cpumask_any_and_distribute(const struct cpumask *src1p,
const struct cpumask *src2p);
/**
* for_each_cpu - iterate over every cpu in a mask