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SubjectRe: [patch 1/2] mm, page_alloc: extend kernelcore and movablecore for percent
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On 02/12/2018 04:24 PM, David Rientjes wrote:
> Both kernelcore= and movablecore= can be used to define the amount of
> ZONE_NORMAL and ZONE_MOVABLE on a system, respectively. This requires
> the system memory capacity to be known when specifying the command line,
> however.
>
> This introduces the ability to define both kernelcore= and movablecore=
> as a percentage of total system memory. This is convenient for systems
> software that wants to define the amount of ZONE_MOVABLE, for example, as
> a proportion of a system's memory rather than a hardcoded byte value.
>
> To define the percentage, the final character of the parameter should be
> a '%'.
>
> Signed-off-by: David Rientjes <rientjes@google.com>
> ---
> Documentation/admin-guide/kernel-parameters.txt | 44 ++++++++++++-------------
> mm/page_alloc.c | 43 +++++++++++++++++++-----
> 2 files changed, 57 insertions(+), 30 deletions(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1825,30 +1825,30 @@
> keepinitrd [HW,ARM]
>
> kernelcore= [KNL,X86,IA-64,PPC]
> - Format: nn[KMGTPE] | "mirror"
> - This parameter
> - specifies the amount of memory usable by the kernel
> - for non-movable allocations. The requested amount is
> - spread evenly throughout all nodes in the system. The
> - remaining memory in each node is used for Movable
> - pages. In the event, a node is too small to have both
> - kernelcore and Movable pages, kernelcore pages will
> - take priority and other nodes will have a larger number
> - of Movable pages. The Movable zone is used for the
> - allocation of pages that may be reclaimed or moved
> - by the page migration subsystem. This means that
> - HugeTLB pages may not be allocated from this zone.
> - Note that allocations like PTEs-from-HighMem still
> - use the HighMem zone if it exists, and the Normal
> - zone if it does not.
> -
> - Instead of specifying the amount of memory (nn[KMGTPE]),
> - you can specify "mirror" option. In case "mirror"
> + Format: nn[KMGTPE] | nn% | "mirror"
> + This parameter specifies the amount of memory usable by
> + the kernel for non-movable allocations. The requested
> + amount is spread evenly throughout all nodes in the
> + system as ZONE_NORMAL. The remaining memory is used for
> + movable memory in its own zone, ZONE_MOVABLE. In the
> + event, a node is too small to have both ZONE_NORMAL and
> + ZONE_MOVABLE, kernelcore memory will take priority and
> + other nodes will have a larger ZONE_MOVABLE.
> +
> + ZONE_MOVABLE is used for the allocation of pages that
> + may be reclaimed or moved by the page migration
> + subsystem. This means that HugeTLB pages may not be
> + allocated from this zone. Note that allocations like
> + PTEs-from-HighMem still use the HighMem zone if it
> + exists, and the Normal zone if it does not.

I know you are just updating the documentation for the new ability to
specify a percentage. However, while looking at this I noticed that
the existing description is out of date. HugeTLB pages CAN be treated
as movable and allocated from ZONE_MOVABLE.

If you have to respin, could you drop that line while making this change?

> +
> + It is possible to specify the exact amount of memory in
> + the form of "nn[KMGTPE]", a percentage of total system
> + memory in the form of "nn%", or "mirror". If "mirror"
> option is specified, mirrored (reliable) memory is used
> for non-movable allocations and remaining memory is used
> - for Movable pages. nn[KMGTPE] and "mirror" are exclusive,
> - so you can NOT specify nn[KMGTPE] and "mirror" at the same
> - time.
> + for Movable pages. "nn[KMGTPE]", "nn%", and "mirror"
> + are exclusive, so you cannot specify multiple forms.
>
> kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
> Format: <Controller#>[,poll interval]

Don't you need to make the same type percentage changes for 'movablecore='?

--
Mike Kravetz

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