Messages in this thread | | | Subject | Re: [PATCH v2 0/4] arm64: drop pfn_valid_within() and simplify pfn_valid() | From | Kefeng Wang <> | Date | Thu, 22 Apr 2021 15:00:20 +0800 |
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On 2021/4/21 14:51, Mike Rapoport wrote: > From: Mike Rapoport <rppt@linux.ibm.com> > > Hi, > > These patches aim to remove CONFIG_HOLES_IN_ZONE and essentially hardwire > pfn_valid_within() to 1. > > The idea is to mark NOMAP pages as reserved in the memory map and restore > the intended semantics of pfn_valid() to designate availability of struct > page for a pfn. > > With this the core mm will be able to cope with the fact that it cannot use > NOMAP pages and the holes created by NOMAP ranges within MAX_ORDER blocks > will be treated correctly even without the need for pfn_valid_within. > > The patches are only boot tested on qemu-system-aarch64 so I'd really > appreciate memory stress tests on real hardware. > > If this actually works we'll be one step closer to drop custom pfn_valid() > on arm64 altogether.
Hi Mike,I have a question, without HOLES_IN_ZONE, the pfn_valid_within() in move_freepages_block()->move_freepages() will be optimized, if there are holes in zone, the 'struce page'(memory map) for pfn range of hole will be free by free_memmap(), and then the page traverse in the zone(with holes) from move_freepages() will meet the wrong page, then it could panic at PageLRU(page) test, check link[1],
"The idea is to mark NOMAP pages as reserved in the memory map", I see the patch2 check memblock_is_nomap() in memory region of memblock, but it seems that memblock_mark_nomap() is not called(maybe I missed), then memmap_init_reserved_pages() won't work, so should the HOLES_IN_ZONE still be needed for generic mm code?
[1] https://lore.kernel.org/linux-arm-kernel/541193a6-2bce-f042-5bb2-88913d5f1047@arm.com/
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