# Introduce Add PR_NUMA_BALANCING in prctl. A large number of page faults will cause performance loss when numa balancing is performing. Thus those processes which care about worst-case performance need numa balancing disabled. Others, on the contrary, allow a temporary performance loss in exchange for higher average performance, so enable numa balancing is better for them. Numa balancing can only be controlled globally by /proc/sys/kernel/numa_balancing. Due to the above case, we want to disable/enable numa_balancing per-process instead. Set per-process numa balancing: prctl(PR_NUMA_BALANCING, PR_SET_NUMA_BALANCING_DISABLE); //disable prctl(PR_NUMA_BALANCING, PR_SET_NUMA_BALANCING_ENABLE); //enable prctl(PR_NUMA_BALANCING, PR_SET_NUMA_BALANCING_DEFAULT); //follow global Get numa_balancing state: prctl(PR_NUMA_BALANCING, PR_GET_NUMA_BALANCING, &ret); cat /proc/<pid>/status | grep NumaB_mode # Unixbench This is overhead of this patch, not performance improvement. +-------------------+----------+ | NAME | OVERHEAD | +-------------------+----------+ | Pipe_Throughput | 0.98% | | Context_Switching | -0.96% | | Process_Creation | 1.18% | +-------------------+----------+ # Changes Changes in v6: - rebase on top of next-20230411 - run Unixbench on physical machine - acked by John Hubbard <jhubbard@xxxxxxxxxx> Changes in v5: - replace numab_enabled with numa_balancing_mode (Peter Zijlstra) - make numa_balancing_enabled and numa_balancing_mode inline (Peter Zijlstra) - use static_branch_inc/dec instead of static_branch_enable/disable (Peter Zijlstra) - delete CONFIG_NUMA_BALANCING in task_tick_fair (Peter Zijlstra) - reword commit, use imperative mood (Bagas Sanjaya) - Unixbench overhead result Changes in v4: - code clean: add wrapper function `numa_balancing_enabled` Changes in v3: - Fix compile error. Changes in v2: - Now PR_NUMA_BALANCING support three states: enabled, disabled, default. enabled and disabled will ignore global setting, and default will follow global setting. Gang Li (2): sched/numa: use static_branch_inc/dec for sched_numa_balancing sched/numa: add per-process numa_balancing Documentation/filesystems/proc.rst | 2 ++ fs/proc/task_mmu.c | 20 ++++++++++++ include/linux/mm_types.h | 3 ++ include/linux/sched/numa_balancing.h | 45 ++++++++++++++++++++++++++ include/uapi/linux/prctl.h | 8 +++++ kernel/fork.c | 4 +++ kernel/sched/core.c | 26 +++++++-------- kernel/sched/fair.c | 9 +++--- kernel/sys.c | 47 ++++++++++++++++++++++++++++ mm/mprotect.c | 6 ++-- 10 files changed, 151 insertions(+), 19 deletions(-) -- 2.20.1
