Changelog since v2 o Remove unnecessary parameters o Update nr during scan only when scanning for cpus
Changlog since v1 o Move extern declaration to header for coding style o Remove unnecessary parameter from __select_idle_cpu This series of 5 patches reposts three patches from Peter entitled "select_idle_sibling() wreckage". It only scans the runqueues in a single pass when searching for an idle sibling. Two patches from Peter were dropped. The first patch altered how scan depth was calculated. Scan depth deletion is a random number generator with two major limitations. The avg_idle time is based on the time between a CPU going idle and being woken up clamped approximately by 2*sysctl_sched_migration_cost. This is difficult to compare in a sensible fashion to avg_scan_cost. The second issue is that only the avg_scan_cost of scan failures is recorded and it does not decay. This requires deeper surgery that would justify a patch on its own although Peter notes that https://lkml.kernel.org/r/20180530143105.977759...@infradead.org is potentially useful for an alternative avg_idle metric. The second patch dropped converted the idle core scan throttling mechanism to SIS_PROP. While this would unify the throttling of core and CPU scanning, it was not free of regressions and has_idle_cores is a fairly effective throttling mechanism with the caveat that it can have a lot of false positives for workloads like hackbench. Peter's series tried to solve three problems at once, this subset addresses one problem. As with anything select_idle_sibling, it's a mix of wins and losses but won more than it lost across a range of workloads and machines. kernel/sched/core.c | 18 +++-- kernel/sched/fair.c | 161 ++++++++++++++++++++-------------------- kernel/sched/features.h | 1 - kernel/sched/sched.h | 2 + 4 files changed, 95 insertions(+), 87 deletions(-) -- 2.26.2
