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zswap_invalidation simply calls xa_erase, which acquires the Xarray lock first, then does a look up. This has a higher overhead even if zswap is not used or the tree is empty. So instead, do a very lightweight xa_empty check first, if there is nothing to erase, don't touch the lock or the tree. Using xa_empty rather than zswap_never_enabled is more helpful as it cover both case where zswap wes never used or the particular range doesn't have any zswap entry. And it's safe as the swap slot should be currently pinned by caller with HAS_CACHE. Sequential SWAP in/out tests with zswap disabled showed a minor performance gain, SWAP in of zero page with zswap enabled also showed a performance gain. (swapout is basically unchanged so only test one case): Swapout of 2G zero page using brd as SWAP, zswap disabled (total time, 4 testrun, +0.1%): Before: 1705013 us 1703119 us 1704335 us 1705848 us. After: 1703579 us |
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| fs | ||
| include | ||
| init | ||
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| ipc | ||
| kernel | ||
| lib | ||
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| .editorconfig | ||
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| COPYING | ||
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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 reStructuredText 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.