Messages in this thread | | | Date | Tue, 30 Jun 2015 12:46:54 +0200 | From | Ingo Molnar <> | Subject | Re: [RFC v2 PATCH 0/8] mm: mirrored memory support for page buddy allocations |
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* Mel Gorman <mgorman@suse.de> wrote:
> [...] > > Basically, overall I feel this series is the wrong approach but not knowing who > the users are making is much harder to judge. I strongly suspect that if > mirrored memory is to be properly used then it needs to be available before the > page allocator is even active. Once active, there needs to be controlled access > for allocation requests that are really critical to mirror and not just all > kernel allocations. None of that would use a MIGRATE_TYPE approach. It would be > alterations to the bootmem allocator and access to an explicit reserve that is > not accounted for as "free memory" and accessed via an explicit GFP flag.
So I think the main goal is to avoid kernel crashes when a #MC memory fault arrives on a piece of memory that is owned by the kernel.
In that sense 'protecting' all kernel allocations is natural: we don't know how to recover from faults that affect kernel memory.
We do know how to recover from faults that affect user-space memory alone.
So if a mechanism is in place that prioritizes 3 groups of allocators:
- non-recoverable memory (kernel allocations mostly)
- high priority user memory (critical apps that must never fail)
- recoverable user memory (non-dirty caches that can simply be dropped, non-critical apps, etc.)
then we can make use of this hardware feature. I suspect this series tries to move in that direction.
Thanks,
Ingo
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