Re: [PATCH v2 1/1] mm: report per-page metadata information

[Sourav Panda <souravpanda@google.com>]

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Hi Greg,

Thank you very much for reviewing my patch. I removed the other style
errors pointed by checkpatch.pl but missed this one. My bad! I will fix it
in version 3.

With regards,
Sourav Panda

On Wed, Oct 18, 2023 at 12:52 AM Greg KH <gregkh@linuxfoundation.org> wrote:

> On Tue, Oct 17, 2023 at 05:55:48PM -0700, Sourav Panda wrote:
> > Adds a new per-node PageMetadata field to
> > /sys/devices/system/node/nodeN/meminfo
> > and a global PageMetadata field to /proc/meminfo. This information can
> > be used by users to see how much memory is being used by per-page
> > metadata, which can vary depending on build configuration, machine
> > architecture, and system use.
> >
> > Per-page metadata is the amount of memory that Linux needs in order to
> > manage memory at the page granularity. The majority of such memory is
> > used by "struct page" and "page_ext" data structures. In contrast to
> > most other memory consumption statistics, per-page metadata might not
> > be included in MemTotal. For example, MemTotal does not include memblock
> > allocations but includes buddy allocations. While on the other hand,
> > per-page metadata would include both memblock and buddy allocations.
> >
> > This memory depends on build configurations, machine architectures, and
> > the way system is used:
> >
> > Build configuration may include extra fields into "struct page",
> > and enable / disable "page_ext"
> > Machine architecture defines base page sizes. For example 4K x86,
> > 8K SPARC, 64K ARM64 (optionally), etc. The per-page metadata
> > overhead is smaller on machines with larger page sizes.
> > System use can change per-page overhead by using vmemmap
> > optimizations with hugetlb pages, and emulated pmem devdax pages.
> > Also, boot parameters can determine whether page_ext is needed
> > to be allocated. This memory can be part of MemTotal or be outside
> > MemTotal depending on whether the memory was hot-plugged, booted with,
> > or hugetlb memory was returned back to the system.
> >
> > Suggested-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> > Signed-off-by: Sourav Panda <souravpanda@google.com>
> > Change-Id: I4351791c9f4c1e9759cbd8e646e808565dbb595f
>
> checkpatch.pl should have said that "Change-Id:" should be removed, why
> didn't you run this on your patch before submitting it?
>
> thanks,
>
> greg k-h
>

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