Re: [RFC PATCH 00/12] mm: mirrored memory support for page buddy allocations

[Xishi Qiu]

On 2015/6/16 15:53, Vlastimil Babka wrote:

> On 06/04/2015 02:54 PM, Xishi Qiu wrote:
>> Intel Xeon processor E7 v3 product family-based platforms introduces support
>> for partial memory mirroring called as 'Address Range Mirroring'. This feature
>> allows BIOS to specify a subset of total available memory to be mirrored (and
>> optionally also specify whether to mirror the range 0-4 GB). This capability
>> allows user to make an appropriate tradeoff between non-mirrored memory range
>> and mirrored memory range thus optimizing total available memory and still
>> achieving highly reliable memory range for mission critical workloads and/or
>> kernel space.
>>
>> Tony has already send a patchset to supprot this feature at boot time.
>> https://lkml.org/lkml/2015/5/8/521
>>
>> This patchset can support the feature after boot time. It introduces mirror_info
>> to save the mirrored memory range. Then use __GFP_MIRROR to allocate mirrored 
>> pages. 
>>
>> I think add a new migratetype is btter and easier than a new zone, so I use
> 
> If the mirrored memory is in a single reasonably compact (no large holes) range
> (per NUMA node) and won't dynamically change its size, then zone might be a
> better option. For one thing, it will still allow distinguishing movable and
> unmovable allocations within the mirrored memory.
> 
> We had enough fun with MIGRATE_CMA and all kinds of checks it added to allocator
> hot paths, and even CMA is now considering moving to a separate zone.
> 

Hi, how about the problem of this case:
e.g. node 0: 0-4G(dma and dma32)
     node 1: 4G-8G(normal), 8-12G(mirror), 12-16G(normal),
so more than one normal zone in a node? or normal zone just span the mirror zone?

Thanks,
Xishi Qiu

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