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Subject[PATCH 2/9] mm, page_alloc: remove boot pageset initialization from memory hotplug
Date
From: Michal Hocko <mhocko@suse.com>

boot_pageset is a boot time hack which gets superseded by normal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.

Changes since v1
- use __maybe_unused for cpu to silence annoying warning for
CONFIG_HAVE_MEMORYLESS_NODES=y

Acked-by: Mel Gorman <mgorman@suse.de>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Michal Hocko <mhocko@suse.com>
---
mm/page_alloc.c | 40 ++++++++++++++++++++++------------------
1 file changed, 22 insertions(+), 18 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index b839a90e24c8..ff53f709c44c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5077,7 +5077,7 @@ DEFINE_MUTEX(zonelists_mutex);
static int __build_all_zonelists(void *data)
{
int nid;
- int cpu;
+ int __maybe_unused cpu;
pg_data_t *self = data;

#ifdef CONFIG_NUMA
@@ -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();
}
--
2.11.0
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