On Tue, 2013-08-27 at 17:37 +0800, Tang Chen wrote:
> After memblock is ready, before SRAT is parsed, we should allocate memory
> near the kernel image. So this patch does the following:
>
> 1. After memblock is ready, make memblock allocate memory from low address
> to high, and set the lowest limit to the end of kernel image.
> 2. After SRAT is parsed, make memblock behave as default, allocate memory
> from high address to low, and reset the lowest limit to 0.
>
> This behavior is controlled by movablenode boot option.
>
> Signed-off-by: Tang Chen <tangchen@xxxxxxxxxxxxxx>
> Reviewed-by: Zhang Yanfei <zhangyanfei@xxxxxxxxxxxxxx>
> ---
> arch/x86/kernel/setup.c | 37 +++++++++++++++++++++++++++++++++++++
> 1 files changed, 37 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index fa7b5f0..0b35bbd 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -1087,6 +1087,31 @@ void __init setup_arch(char **cmdline_p)
> trim_platform_memory_ranges();
> trim_low_memory_range();
>
> +#ifdef CONFIG_MOVABLE_NODE
> + if (movablenode_enable_srat) {
> + /*
> + * Memory used by the kernel cannot be hot-removed because Linux cannot
> + * migrate the kernel pages. When memory hotplug is enabled, we should
> + * prevent memblock from allocating memory for the kernel.
> + *
> + * ACPI SRAT records all hotpluggable memory ranges. But before SRAT is
> + * parsed, we don't know about it.
> + *
> + * The kernel image is loaded into memory at very early time. We cannot
> + * prevent this anyway. So on NUMA system, we set any node the kernel
> + * resides in as un-hotpluggable.
> + *
> + * Since on modern servers, one node could have double-digit gigabytes
> + * memory, we can assume the memory around the kernel image is also
Memory hotplug can be supported on virtualized environments, and we
should allow using SRAT on them as a next step. In such environments,
memory hotplug will be performed on per memory device object basis for
workload balancing, and double-digit gigabytes is unlikely the case for
now. So, I'd suggest it should instead state that all allocations are
kept small until SRAT is pursed.
> + * un-hotpluggable. So before SRAT is parsed, just allocate memory near
> + * the kernel image to try the best to keep the kernel away from
> + * hotpluggable memory.
> + */
> + memblock_set_current_order(MEMBLOCK_ORDER_LOW_TO_HIGH);
> + memblock_set_current_limit_low(__pa_symbol(_end));
> + }
> +#endif /* CONFIG_MOVABLE_NODE */
Should the above block be put into init_mem_mapping() since it is
memblock initialization? It is good to have some concise comments here,
though.
> +
> init_mem_mapping();
>
> early_trap_pf_init();
> @@ -1127,6 +1152,18 @@ void __init setup_arch(char **cmdline_p)
> early_acpi_boot_init();
>
> initmem_init();
> +
> +#ifdef CONFIG_MOVABLE_NODE
> + if (movablenode_enable_srat) {
> + /*
> + * When ACPI SRAT is parsed, which is done in initmem_init(), set
> + * memblock back to the default behavior.
> + */
> + memblock_set_current_order(MEMBLOCK_ORDER_DEFAULT);
> + memblock_set_current_limit_low(0);
> + }
> +#endif /* CONFIG_MOVABLE_NODE */
Similarly, should this block be put into initmem_init() with some
comment here?
Thanks,
-Toshi
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