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3917c80280
Currently we have different copy-on-write semantics for anon- and file-THP. For anon-THP we try to allocate huge page on the write fault, but on file-THP we split PMD and allocate 4k page. Arguably, file-THP semantics is more desirable: we don't necessary want to unshare full PMD range from the parent on the first access. This is the primary reason THP is unusable for some workloads, like Redis. The original THP refcounting didn't allow to have PTE-mapped compound pages, so we had no options, but to allocate huge page on CoW (with fallback to 512 4k pages). The current refcounting doesn't have such limitations and we can cut a lot of complex code out of fault path. khugepaged is now able to recover THP from such ranges if the configuration allows. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Tested-by: Zi Yan <ziy@nvidia.com> Reviewed-by: William Kucharski <william.kucharski@oracle.com> Reviewed-by: Zi Yan <ziy@nvidia.com> Acked-by: Yang Shi <yang.shi@linux.alibaba.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Ralph Campbell <rcampbell@nvidia.com> Link: http://lkml.kernel.org/r/20200416160026.16538-8-kirill.shutemov@linux.intel.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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| fs | ||
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| init | ||
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| kernel | ||
| lib | ||
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| README | ||
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.