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.
Huang Ying
authored
With commit 09854ba9 ("mm: do_wp_page() simplification"), after COW, the idle swap cache page (neither the page nor the corresponding swap entry is mapped by any process) will be left in the LRU list, even if it's in the active list or the head of the inactive list. So, the page reclaimer may take quite some overhead to reclaim these actually unused pages. To help the page reclaiming, in this patch, after COW, the idle swap cache page will be tried to be freed. To avoid to introduce much overhead to the hot COW code path, a) there's almost zero overhead for non-swap case via checking PageSwapCache() firstly. b) the page lock is acquired via trylock only. To test the patch, we used pmbench memory accessing benchmark with working-set larger than available memory on a 2-socket Intel server with a NVMe SSD as swap device. Test results shows that the pmbench score increases up to 23.8% with the decreased size of swap cache and swapin throughput. Link: https://lkml.kernel.org/r/20210601053143.1380078-1-ying.huang@intel.com Signed-off-by:"Huang, Ying" <ying.huang@intel.com> Suggested-by: Johannes Weiner <hannes@cmpxchg.org> [use free_swap_cache()] Acked-by:
Johannes Weiner <hannes@cmpxchg.org> Cc: Hugh Dickins <hughd@google.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Peter Xu <peterx@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Rik van Riel <riel@surriel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Tim Chen <tim.c.chen@intel.com> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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