On 07/14/2017 09:59 AM, Michal Hocko wrote:
> From: Michal Hocko <mhocko@xxxxxxxx>
>
> boot_pageset is a boot time hack which gets superseded by normal
> pagesets later in the boot process. It makes zero sense to reinitialize
> it again and again during memory hotplug.
>
> Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
> ---
> mm/page_alloc.c | 38 +++++++++++++++++++++-----------------
> 1 file changed, 21 insertions(+), 17 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index d9f4ea057e74..7746824a425d 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -5098,23 +5098,8 @@ static int __build_all_zonelists(void *data)
> }
> }
>
> - /*
> - * Initialize the boot_pagesets that are going to be used
> - * for bootstrapping processors. The real pagesets for
> - * each zone will be allocated later when the per cpu
> - * allocator is available.
> - *
> - * boot_pagesets are used also for bootstrapping offline
> - * cpus if the system is already booted because the pagesets
> - * are needed to initialize allocators on a specific cpu too.
> - * F.e. the percpu allocator needs the page allocator which
> - * needs the percpu allocator in order to allocate its pagesets
> - * (a chicken-egg dilemma).
> - */
> - for_each_possible_cpu(cpu) {
> - setup_pageset(&per_cpu(boot_pageset, cpu), 0);
> -
> #ifdef CONFIG_HAVE_MEMORYLESS_NODES
> + for_each_possible_cpu(cpu) {
> /*
> * We now know the "local memory node" for each node--
> * i.e., the node of the first zone in the generic zonelist.
> @@ -5125,8 +5110,8 @@ static int __build_all_zonelists(void *data)
> */
> if (cpu_online(cpu))
> set_cpu_numa_mem(cpu, local_memory_node(cpu_to_node(cpu)));
> -#endif
> }
> +#endif
>
> return 0;
> }
> @@ -5134,7 +5119,26 @@ static int __build_all_zonelists(void *data)
> static noinline void __init
> build_all_zonelists_init(void)
> {
> + int cpu;
> +
> __build_all_zonelists(NULL);
> +
> + /*
> + * Initialize the boot_pagesets that are going to be used
> + * for bootstrapping processors. The real pagesets for
> + * each zone will be allocated later when the per cpu
> + * allocator is available.
> + *
> + * boot_pagesets are used also for bootstrapping offline
> + * cpus if the system is already booted because the pagesets
> + * are needed to initialize allocators on a specific cpu too.
> + * F.e. the percpu allocator needs the page allocator which
> + * needs the percpu allocator in order to allocate its pagesets
> + * (a chicken-egg dilemma).
> + */
> + for_each_possible_cpu(cpu)
> + setup_pageset(&per_cpu(boot_pageset, cpu), 0);
> +
> mminit_verify_zonelist();
> cpuset_init_current_mems_allowed();
> }
>
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