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Subject[PATCH 4.2.y-ckt 55/59] mm: update min_free_kbytes from khugepaged after core initialization
Date
4.2.8-ckt10 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Jason Baron <jbaron@akamai.com>

commit bc22af74f271ef76b2e6f72f3941f91f0da3f5f8 upstream.

Khugepaged attempts to raise min_free_kbytes if its set too low.
However, on boot khugepaged sets min_free_kbytes first from
subsys_initcall(), and then the mm 'core' over-rides min_free_kbytes
after from init_per_zone_wmark_min(), via a module_init() call.

Khugepaged used to use a late_initcall() to set min_free_kbytes (such
that it occurred after the core initialization), however this was
removed when the initialization of min_free_kbytes was integrated into
the starting of the khugepaged thread.

The fix here is simply to invoke the core initialization using a
core_initcall() instead of module_init(), such that the previous
initialization ordering is restored. I didn't restore the
late_initcall() since start_stop_khugepaged() already sets
min_free_kbytes via set_recommended_min_free_kbytes().

This was noticed when we had a number of page allocation failures when
moving a workload to a kernel with this new initialization ordering. On
an 8GB system this restores min_free_kbytes back to 67584 from 11365
when CONFIG_TRANSPARENT_HUGEPAGE=y is set and either
CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS=y or
CONFIG_TRANSPARENT_HUGEPAGE_MADVISE=y.

Fixes: 79553da293d3 ("thp: cleanup khugepaged startup")
Signed-off-by: Jason Baron <jbaron@akamai.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
mm/page_alloc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 240c22d..6d95dea 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6319,7 +6319,7 @@ int __meminit init_per_zone_wmark_min(void)
setup_per_zone_inactive_ratio();
return 0;
}
-module_init(init_per_zone_wmark_min)
+core_initcall(init_per_zone_wmark_min)

/*
* min_free_kbytes_sysctl_handler - just a wrapper around proc_dointvec() so
--
2.7.4
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