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SubjectRe: [PATCH v3] mm: hugetlb: optionally allocate gigantic hugepages using cma 65;5803;1c Commit 944d9fec8d7a ("hugetlb: add support for gigantic page allocation at runtime") has added the run-time allocation of gigantic pages. However it actually works on
On Wed, 11 Mar 2020 15:09:20 -0700 Roman Gushchin <guro@fb.com> wrote:

> At large scale rebooting servers in order to allocate gigantic hugepages
> is quite expensive and complex. At the same time keeping some constant
> percentage of memory in reserved hugepages even if the workload isn't
> using it is a big waste: not all workloads can benefit from using 1 GB
> pages.
>
> The following solution can solve the problem:
> 1) On boot time a dedicated cma area* is reserved. The size is passed
> as a kernel argument.
> 2) Run-time allocations of gigantic hugepages are performed using the
> cma allocator and the dedicated cma area
>
> In this case gigantic hugepages can be allocated successfully with a
> high probability, however the memory isn't completely wasted if nobody
> is using 1GB hugepages: it can be used for pagecache, anon memory,
> THPs, etc.
>
> * On a multi-node machine a per-node cma area is allocated on each node.
> Following gigantic hugetlb allocation are using the first available
> numa node if the mask isn't specified by a user.
>
> Usage:
> 1) configure the kernel to allocate a cma area for hugetlb allocations:
> pass hugetlb_cma=10G as a kernel argument
>
> 2) allocate hugetlb pages as usual, e.g.
> echo 10 > /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages
>
> If the option isn't enabled or the allocation of the cma area failed,
> the current behavior of the system is preserved.
>
> x86 and arm-64 are covered by this patch, other architectures can be
> trivially added later.

Lots of review input on v2, but then everyone went quiet ;)

Has everything been addressed?

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