On Tue, 12 Apr 2016, Jason Baron wrote: > 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 <jba...@akamai.com>
Acked-by: David Rientjes <rient...@google.com> I assume it could also be fixed by not setting min_free_kbytes lower in init_per_zone_wmark_min(), but if the ordering is correct this is less code.