* Mel Gorman <[email protected]> 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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