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Date: Wed, 7 Dec 2016 00:43:01 -0800 From: Scott Branden <scott.branden@...adcom.com> To: Xishi Qiu <qiuxishi@...wei.com> Cc: Arnd Bergmann <arnd@...db.de>, Russell King <linux@...linux.org.uk>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <will.deacon@....com>, Ard Biesheuvel <ard.biesheuvel@...aro.org>, Mark Rutland <mark.rutland@....com>, bielski@...tmail.net, BCM Kernel Feedback <bcm-kernel-feedback-list@...adcom.com>, Tang Chen <tangchen@...fujitsu.com>, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org Subject: Re: [RFC PATCH 0/2] arm64: memory-hotplug: Add Memory Hotplug support Hi Xishi, I followed you suggestions and found pfn_valid is always true. Answers to your questions inline. I could keep debugging this but hope Marcin sends out some code - I'm quite willing to test and help clean up the patchset. On 16-12-01 07:11 PM, Xishi Qiu wrote: > On 2016/12/2 10:38, Scott Branden wrote: > >> Hi Xishi, >> >> Thanks for the reply - please see comments below. >> >> On 16-12-01 05:49 PM, Xishi Qiu wrote: >>> On 2016/12/2 8:19, Scott Branden wrote: >>> >>>> This patchset is sent for comment to add memory hotplug support for ARM64 >>>> based platforms. It follows hotplug code added for other architectures >>>> in the linux kernel. >>>> >>>> I tried testing the memory hotplug feature following documentation from >>>> Documentation/memory-hotplug.txt. I don't think it is working as expected >>>> - see below: >>>> >>>> To add memory to the system I did the following: >>>> echo 0x400000000 > /sys/devices/system/memory/probe >>>> >>>> The memory is displayed as system ram: >>>> cat /proc/iomem: >>>> 74000000-77ffffff : System RAM >>>> 74080000-748dffff : Kernel code >>>> 74950000-749d2fff : Kernel data >>>> 400000000-43fffffff : System RAM >>>> >>>> But does not seem to be added to the kernel memory. >>>> /proc/meminfo did not change. >>>> >>>> What else needs to be done so the memory is added to the kernel memory >>>> pool for normal allocation? >>>> >>> >>> Hi Scott, >>> >>> Do you mean it still don't support hod-add after apply this patchset? >> >> After applying the patch it appears to partially support hot-add. Please let me know if you think it is working as expected? >> >> The memory probe functions in that the memory is registered with the system and shows up in /proc/iomem. But, the memory is not available in /proc/meminfo. Do you think something else needs to be adjusted for ARM64 to hotadd the memory >> >> I just found another clue: >> under /sys/devices/system/memory I only see one memory entry (before or after I try to hotadd additional memory). >> >> /sys/devices/system/memory # ls >> auto_online_blocks memory0 uevent >> block_size_bytes probe >> >> In arch/arm64/include/asm/sparsemem.h if I change SECTION_SIZE_BITS from 30 to 28 and recompile I get the following: >> /sys/devices/system/memory # ls >> auto_online_blocks memory7 uevent >> block_size_bytes probe >> >> >> In arch/arm64/include/asm/sparsemem.h if I change SECTION_SIZE_BITS from 30 to 27 and recompile I get the following: >> /sys/devices/system/memory # ls >> auto_online_blocks memory14 uevent >> block_size_bytes probe >> >> If looks to me like something is not working properly in the ARM64 implementation. I should expect to see multiple memoryX entries under /sys/devices/system/memory? >> > > Hi Scott, > > 1. Do you enable the following configs? > CONFIG_SPARSEMEM > MEMORY_HOTPLUG > CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE Yes, these configs are enabled > > 2. I find you missed create mapping in arch_add_memory(), and x86 has it. Could you please explain this further? The patch I submitted hass arch_add_memory identical to the ia64 implementation. > > 3. We will add memblock first, so pfn_valid() maybe always return true(in the > following function), and this will lead __add_section() failed. Please check > it. You are correct - pfn_valid always returns true. The function is in arch/arm64/mm/init.c and different than the one you indicated below: #ifdef CONFIG_HAVE_ARCH_PFN_VALID int pfn_valid(unsigned long pfn) { return memblock_is_map_memory(pfn << PAGE_SHIFT); } EXPORT_SYMBOL(pfn_valid); #endif > > int pfn_valid(unsigned long pfn) > { > return (pfn & PFN_MASK) == pfn && memblock_is_memory(pfn << PAGE_SHIFT); > } > > add_memory > add_memory_resource > memblock_add_node > arch_add_memory > __add_pages > __add_section > pfn_valid > > Thanks, > Xishi Qiu > >> >> >>> >>> Thanks, >>> Xishi Qiu >>> >>>> Scott Branden (2): >>>> arm64: memory-hotplug: Add MEMORY_HOTPLUG, MEMORY_HOTREMOVE, >>>> MEMORY_PROBE >>>> arm64: defconfig: enable MEMORY_HOTPLUG config options >>>> >>>> arch/arm64/Kconfig | 10 ++++++++++ >>>> arch/arm64/configs/defconfig | 3 +++ >>>> arch/arm64/mm/init.c | 42 ++++++++++++++++++++++++++++++++++++++++++ >>>> 3 files changed, 55 insertions(+) >>>> >>> >>> >>> >> >> . >> > > >
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