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6fd3620b34
Currently memmap_init_zone_device() ends up initializing 32768 pages when it only needs to initialize 128 given tail page reuse. That number is worse with 1GB compound pages, 262144 instead of 128. Update memmap_init_zone_device() to skip redundant initialization, detailed below. When a pgmap @vmemmap_shift is set, all pages are mapped at a given huge page alignment and use compound pages to describe them as opposed to a struct per 4K. With @vmemmap_shift > 0 and when struct pages are stored in ram (!altmap) most tail pages are reused. Consequently, the amount of unique struct pages is a lot smaller than the total amount of struct pages being mapped. The altmap path is left alone since it does not support memory savings based on compound pages devmap. Link: https://lkml.kernel.org/r/20220420155310.9712-6-joao.m.martins@oracle.com Signed-off-by: Joao Martins <joao.m.martins@oracle.com> Reviewed-by: Muchun Song <songmuchun@bytedance.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Jane Chu <jane.chu@oracle.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Matthew Wilcox <willy@infradead.org> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Vishal Verma <vishal.l.verma@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.