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Message-ID: <51EC9D6F.9010807@cn.fujitsu.com>
Date: Mon, 22 Jul 2013 10:48:15 +0800
From: Tang Chen <tangchen@...fujitsu.com>
To: tglx@...utronix.de, mingo@...e.hu, hpa@...or.com,
akpm@...ux-foundation.org, tj@...nel.org, trenn@...e.de,
yinghai@...nel.org, jiang.liu@...wei.com, wency@...fujitsu.com,
laijs@...fujitsu.com, isimatu.yasuaki@...fujitsu.com,
izumi.taku@...fujitsu.com, mgorman@...e.de, minchan@...nel.org,
mina86@...a86.com, gong.chen@...ux.intel.com,
vasilis.liaskovitis@...fitbricks.com, lwoodman@...hat.com,
riel@...hat.com, jweiner@...hat.com, prarit@...hat.com,
zhangyanfei@...fujitsu.com, yanghy@...fujitsu.com
CC: x86@...nel.org, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
linux-acpi@...r.kernel.org
Subject: Re: [PATCH 00/21] Arrange hotpluggable memory as ZONE_MOVABLE.
Hi,
Forgot to mention, this patch-set is based on linux-3.10 release.
Thanks. :)
On 07/19/2013 03:59 PM, Tang Chen wrote:
> This patch-set aims to solve some problems at system boot time
> to enhance memory hotplug functionality.
>
> [Background]
>
> The Linux kernel cannot migrate pages used by the kernel because
> of the kernel direct mapping. Since va = pa + PAGE_OFFSET, if the
> physical address is changed, we cannot simply update the kernel
> pagetable. On the contrary, we have to update all the pointers
> pointing to the virtual address, which is very difficult to do.
>
> In order to do memory hotplug, we should prevent the kernel to use
> hotpluggable memory.
>
> In ACPI, there is a table named SRAT(System Resource Affinity Table).
> It contains system NUMA info (CPUs, memory ranges, PXM), and also a
> flag field indicating which memory ranges are hotpluggable.
>
>
> [Problem to be solved]
>
> At the very early time when the system is booting, we use a bootmem
> allocator, named memblock, to allocate memory for the kernel.
> memblock will start to work before the kernel parse SRAT, which
> means memblock won't know which memory is hotpluggable before SRAT
> is parsed.
>
> So at this time, memblock could allocate hotpluggable memory for
> the kernel to use permanently. For example, the kernel may allocate
> pagetables in hotpluggable memory, which cannot be freed when the
> system is up.
>
> So we have to prevent memblock allocating hotpluggable memory for
> the kernel at the early boot time.
>
>
> [Earlier solutions]>
> We have tried to parse SRAT earlier, before memblock is ready. To
> do this, we also have to do ACPI_INITRD_TABLE_OVERRIDE earlier.
> Otherwise the override tables won't be able to effect.
>
> This is not that easy to do because memblock is ready before direct
> mapping is setup. So Yinghai split the ACPI_INITRD_TABLE_OVERRIDE
> procedure into two steps: find and copy. Please refer to the
> following patch-set:
> https://lkml.org/lkml/2013/6/13/587
>
> To this solution, tj gave a lot of comments and the following
> suggestions.
>
>
> [Suggestion from tj]
>
> tj mainly gave the following suggestions:
>
> 1. Necessary reordering is OK, but we should not rely on
> reordering to achieve the goal because it makes the kernel
> too fragile.
>
> 2. Memory allocated to kernel for temporary usage is OK because
> it will be freed when the system is up. Doing relocation
> for permanent allocated hotpluggable memory will make the
> the kernel more robust.
>
> 3. Need to enhance memblock to discover and complain if any
> hotpluggable memory is allocated to kernel.
>
> After a long thinking, we choose not to do the relocation for
> the following reasons:
>
> 1. It's easy to find out the allocated hotpluggable memory. But
> memblock will merge the adjoined ranges owned by different users
> and used for different purposes. It's hard to find the owners.
>
> 2. Different memory has different way to be relocated. I think one
> function for each kind of memory will make the code too messy.
>
> 3. Pagetable could be in hotpluggable memory. Relocating pagetable
> is too difficult and risky. We have to update all PUD, PMD pages.
> And also, ACPI_INITRD_TABLE_OVERRIDE and parsing SRAT procedures
> are not long after pagetable is initialized. If we relocate the
> pagetable not long after it was initialized, the code will be
> very ugly.
>
>
> [Solution in this patch-set]
>
> In this patch-set, we still do the reordering, but in a new way.
>
> 1. Improve memblock with flags, so that it is able to differentiate
> memory regions for different usage. And also a MEMBLOCK_HOTPLUGGABLE
> flag to mark hotpluggable memory.
> (patch 1 ~ 3)
>
> 2. When memblock is ready (memblock_x86_fill() is called), initialize
> acpi_gbl_root_table_list, fulfill all the ACPI tables' phys addrs.
> Now, we have all the ACPI tables' phys addrs provided by firmware.
> (patch 4 ~ 8)
>
> 3. Check if there is a SRAT in initrd file used to override the one
> provided by firmware. If so, get its phys addr.
> (patch 12)
>
> 4. If no override SRAT in initrd, get the phys addr of the SRAT
> provided by firmware.
> (patch 13)
>
> Now, we have the phys addr of the to be used SRAT, the one in
> initrd or the one in firmware.
>
> 5. Parse only the memory affinities in SRAT, find out all the
> hotpluggable memory regions and reserve them in memblock with
> MEMBLK_HOTPLUGGABLE flag.
> (patch 14 ~ 15)
>
> 6. The kernel goes through the current path. Any other related parts,
> such as ACPI_INITRD_TABLE_OVERRIDE path, the current parsing ACPI
> tables pathes, global variable numa_meminfo, and so on, are not
> modified. They work as before.
>
> 7. Free memory with MEMBLK_HOTPLUGGABLE flag when memory initialization
> is finished.
> (patch 16)
>
> 8. Introduce movablecore=acpi boot option to allow users to enable
> and disable this functionality.
> (patch 17 ~ 21)
>
> And patch 9 ~ 11 fix some small problems.
>
>
> In summary, in order to get hotpluggable memory info as early as possible,
> this patch-set only parse memory affinities in SRAT one more time right
> after memblock is ready, and leave all the other pathes untouched. With
> the hotpluggable memory info, we can arrange hotpluggable memory in
> ZONE_MOVABLE to prevent the kernel to use it.
>
> Thanks. :)
>
>
> Tang Chen (20):
> acpi: Print Hot-Pluggable Field in SRAT.
> memblock, numa: Introduce flag into memblock.
> x86, acpi, numa, mem-hotplug: Introduce MEMBLK_HOTPLUGGABLE to
> reserve hotpluggable memory.
> acpi: Remove "continue" in macro INVALID_TABLE().
> acpi: Introduce acpi_invalid_table() to check if a table is invalid.
> x86, acpi: Split acpi_boot_table_init() into two parts.
> x86, acpi: Initialize ACPI root table list earlier.
> x86, acpi: Also initialize signature and length when parsing root
> table.
> x86: Make get_ramdisk_{image|size}() global.
> earlycpio.c: Fix the confusing comment of find_cpio_data().
> x86, acpi: Try to find if SRAT is overrided earlier.
> x86, acpi: Try to find SRAT in firmware earlier.
> x86, acpi, numa: Reserve hotpluggable memory at early time.
> x86, acpi, numa: Don't reserve memory on nodes the kernel resides in.
> x86, memblock, mem-hotplug: Free hotpluggable memory reserved by
> memblock.
> page_alloc, mem-hotplug: Improve movablecore to {en|dis}able using
> SRAT.
> x86, numa: Synchronize nid info in memblock.reserve with
> numa_meminfo.
> x86, numa: Save nid when reserve memory into memblock.reserved[].
> x86, numa, acpi, memory-hotplug: Make movablecore=acpi have higher
> priority.
> doc, page_alloc, acpi, mem-hotplug: Add doc for movablecore=acpi boot
> option.
>
> Yasuaki Ishimatsu (1):
> x86: get pg_data_t's memory from other node
>
> Documentation/kernel-parameters.txt | 10 ++
> arch/x86/include/asm/setup.h | 3 +
> arch/x86/kernel/acpi/boot.c | 38 +++--
> arch/x86/kernel/setup.c | 22 +++-
> arch/x86/mm/numa.c | 55 +++++++-
> arch/x86/mm/srat.c | 11 +-
> drivers/acpi/acpica/tbutils.c | 48 ++++++-
> drivers/acpi/acpica/tbxface.c | 34 +++++
> drivers/acpi/osl.c | 262 ++++++++++++++++++++++++++++++++---
> drivers/acpi/tables.c | 7 +-
> include/acpi/acpixf.h | 6 +
> include/linux/acpi.h | 21 +++-
> include/linux/memblock.h | 9 ++
> include/linux/memory_hotplug.h | 5 +
> include/linux/mm.h | 9 ++
> lib/earlycpio.c | 7 +-
> mm/memblock.c | 90 ++++++++++--
> mm/memory_hotplug.c | 42 ++++++-
> mm/nobootmem.c | 3 +
> mm/page_alloc.c | 44 ++++++-
> 20 files changed, 656 insertions(+), 70 deletions(-)
>
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