Subject: + x86-mem-hotplug-support-initialize-page-tables-in-bottom-up.patch added to -mm tree
To: tangchen@xxxxxxxxxxxxxx,hannes@xxxxxxxxxxx,hpa@xxxxxxxxx,isimatu.yasuaki@xxxxxxxxxxxxxx,izumi.taku@xxxxxxxxxxxxxx,jiang.liu@xxxxxxxxxx,kamezawa.hiroyu@xxxxxxxxxxxxxx,laijs@xxxxxxxxxxxxxx,lenb@xxxxxxxxxx,liwanp@xxxxxxxxxxxxxxxxxx,mgorman@xxxxxxx,mina86@xxxxxxxxxx,minchan@xxxxxxxxxx,mingo@xxxxxxx,riel@xxxxxxxxxx,rjw@xxxxxxx,tglx@xxxxxxxxxxxxx,tj@xxxxxxxxxx,toshi.kani@xxxxxx,trenn@xxxxxxx,wency@xxxxxxxxxxxxxx,yinghai@xxxxxxxxxx,zhangyanfei@xxxxxxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Wed, 25 Sep 2013 17:05:26 -0700
The patch titled
Subject: x86/mem-hotplug: support initializing page tables in bottom-up mode
has been added to the -mm tree. Its filename is
x86-mem-hotplug-support-initialize-page-tables-in-bottom-up.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/x86-mem-hotplug-support-initialize-page-tables-in-bottom-up.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/x86-mem-hotplug-support-initialize-page-tables-in-bottom-up.patch
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From: Tang Chen <tangchen@xxxxxxxxxxxxxx>
Subject: x86/mem-hotplug: support initializing page tables in bottom-up mode
The Linux kernel cannot migrate pages used by the kernel. As a result,
kernel pages cannot be hot-removed. So we cannot allocate hotpluggable
memory for the kernel.
In a memory hotplug system, any numa node the kernel resides in should be
unhotpluggable. And for a modern server, each node could have at least
16GB memory. So memory around the kernel image is highly likely
unhotpluggable.
ACPI SRAT (System Resource Affinity Table) contains the memory hotplug
info. But before SRAT is parsed, memblock has already started to allocate
memory for the kernel. So we need to prevent memblock from doing this.
So direct memory mapping page tables setup is the case.
init_mem_mapping() is called before SRAT is parsed. To prevent page
tables being allocated within hotpluggable memory, we will use bottom-up
direction to allocate page tables from the end of kernel image to the
higher memory.
Signed-off-by: Tang Chen <tangchen@xxxxxxxxxxxxxx>
Signed-off-by: Zhang Yanfei <zhangyanfei@xxxxxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: "Rafael J . Wysocki" <rjw@xxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Jiang Liu <jiang.liu@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
Cc: Len Brown <lenb@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Michal Nazarewicz <mina86@xxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Taku Izumi <izumi.taku@xxxxxxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Thomas Renninger <trenn@xxxxxxx>
Cc: Toshi Kani <toshi.kani@xxxxxx>
Cc: Wanpeng Li <liwanp@xxxxxxxxxxxxxxxxxx>
Cc: Wen Congyang <wency@xxxxxxxxxxxxxx>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
Cc: Yinghai Lu <yinghai@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/x86/mm/init.c | 64 +++++++++++++++++++++++++++++++++++++++++--
1 file changed, 62 insertions(+), 2 deletions(-)
diff -puN arch/x86/mm/init.c~x86-mem-hotplug-support-initialize-page-tables-in-bottom-up arch/x86/mm/init.c
--- a/arch/x86/mm/init.c~x86-mem-hotplug-support-initialize-page-tables-in-bottom-up
+++ a/arch/x86/mm/init.c
@@ -456,6 +456,48 @@ static void __init memory_map_top_down(u
init_range_memory_mapping(real_end, map_end);
}
+/**
+ * memory_map_bottom_up - Map [map_start, map_end) bottom up
+ * @map_start: start address of the target memory range
+ * @map_end: end address of the target memory range
+ *
+ * This function will setup direct mapping for memory range
+ * [map_start, map_end) in bottom-up.
+ */
+static void __init memory_map_bottom_up(unsigned long map_start,
+ unsigned long map_end)
+{
+ unsigned long next, new_mapped_ram_size, start;
+ unsigned long mapped_ram_size = 0;
+ /* step_size need to be small so pgt_buf from BRK could cover it */
+ unsigned long step_size = PMD_SIZE;
+
+ start = map_start;
+ min_pfn_mapped = start >> PAGE_SHIFT;
+
+ /*
+ * We start from the bottom (@map_start) and go to the top (@map_end).
+ * The memblock_find_in_range() gets us a block of RAM from the
+ * end of RAM in [min_pfn_mapped, max_pfn_mapped) used as new pages
+ * for page table.
+ */
+ while (start < map_end) {
+ if (map_end - start > step_size) {
+ next = round_up(start + 1, step_size);
+ if (next > map_end)
+ next = map_end;
+ } else
+ next = map_end;
+
+ new_mapped_ram_size = init_range_memory_mapping(start, next);
+ start = next;
+
+ if (new_mapped_ram_size > mapped_ram_size)
+ step_size <<= STEP_SIZE_SHIFT;
+ mapped_ram_size += new_mapped_ram_size;
+ }
+}
+
void __init init_mem_mapping(void)
{
unsigned long end;
@@ -471,8 +513,26 @@ void __init init_mem_mapping(void)
/* the ISA range is always mapped regardless of memory holes */
init_memory_mapping(0, ISA_END_ADDRESS);
- /* setup direct mapping for range [ISA_END_ADDRESS, end) in top-down*/
- memory_map_top_down(ISA_END_ADDRESS, end);
+ /*
+ * If the allocation is in bottom-up direction, we setup direct mapping
+ * in bottom-up, otherwise we setup direct mapping in top-down.
+ */
+ if (memblock_bottom_up()) {
+ unsigned long kernel_end;
+
+ kernel_end = __pa_symbol(_end);
+ /*
+ * we need two separate calls here. This is because we want to
+ * allocate page tables above the kernel. So we first map
+ * [kernel_end, end) to make memory above the kernel be mapped
+ * as soon as possible. And then use page tables allocated above
+ * the kernel to map [ISA_END_ADDRESS, kernel_end).
+ */
+ memory_map_bottom_up(kernel_end, end);
+ memory_map_bottom_up(ISA_END_ADDRESS, kernel_end);
+ } else {
+ memory_map_top_down(ISA_END_ADDRESS, end);
+ }
#ifdef CONFIG_X86_64
if (max_pfn > max_low_pfn) {
_
Patches currently in -mm which might be from tangchen@xxxxxxxxxxxxxx are
memblock-factor-out-of-top-down-allocation.patch
memblock-introduce-bottom-up-allocation-mode.patch
x86-mm-factor-out-of-top-down-direct-mapping-setup.patch
x86-mem-hotplug-support-initialize-page-tables-in-bottom-up.patch
x86-acpi-crash-kdump-do-reserve_crashkernel-after-srat-is-parsed.patch
mem-hotplug-introduce-movablenode-boot-option.patch
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