Messages in this thread | | | Subject | Re: [PATCH v9 08/12] mm: zero reserved and unavailable struct pages | From | Pasha Tatashin <> | Date | Tue, 3 Oct 2017 11:29:16 -0400 |
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On 10/03/2017 09:18 AM, Michal Hocko wrote: > On Wed 20-09-17 16:17:10, Pavel Tatashin wrote: >> Some memory is reserved but unavailable: not present in memblock.memory >> (because not backed by physical pages), but present in memblock.reserved. >> Such memory has backing struct pages, but they are not initialized by going >> through __init_single_page(). > > Could you be more specific where is such a memory reserved? >
I know of one example: trim_low_memory_range() unconditionally reserves from pfn 0, but e820__memblock_setup() might provide the exiting memory from pfn 1 (i.e. KVM).
But, there could be more based on this comment from linux/page-flags.h:
19 * PG_reserved is set for special pages, which can never be swapped out. Some 20 * of them might not even exist (eg empty_bad_page)...
Pasha
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