Re: [PATCH v5] mm: Proactive compaction

[Nitin Gupta <ngupta@nitingupta.dev>]

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On Mon, May 18, 2020 at 11:14 AM Nitin Gupta <nigupta@nvidia.com> wrote:

> For some applications, we need to allocate almost all memory as
> hugepages. However, on a running system, higher-order allocations can
> fail if the memory is fragmented. Linux kernel currently does on-demand
> compaction as we request more hugepages, but this style of compaction
> incurs very high latency. Experiments with one-time full memory
> compaction (followed by hugepage allocations) show that kernel is able
> to restore a highly fragmented memory state to a fairly compacted memory
> state within <1 sec for a 32G system. Such data suggests that a more
> proactive compaction can help us allocate a large fraction of memory as
> hugepages keeping allocation latencies low.
>
> For a more proactive compaction, the approach taken here is to define
> a new tunable called 'proactiveness' which dictates bounds for external
> fragmentation wrt HUGETLB_PAGE_ORDER order which kcompactd tries to
> maintain.
>
> The tunable is exposed through sysctl:
>   /proc/sys/vm/compaction_proactiveness
>
> It takes value in range [0, 100], with a default of 20.
>
>

Ping.

Any comments/feedback for this v5 patch?


Thanks,
Nitin

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