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924a11bd16
Since merged pages are copied every time they need to be modified, the write access time is different between shared and non-shared pages. Add ksm_cow_time() function which evaluates latency of these COW breaks. First, 4000 pages are allocated and the time, required to modify 1 byte in every other page, is measured. After this, the pages are merged into 2000 pairs and in each pair, 1 page is modified (i.e. they are decoupled) to detect COW breaks. The time needed to break COW of merged pages is then compared with performance of non-shared pages. The test is run as follows: ./ksm_tests -C The output: Total size: 15 MiB Not merged pages: Total time: 0.002185489 s Average speed: 3202.945 MiB/s Merged pages: Total time: 0.004386872 s Average speed: 1595.670 MiB/s Link: https://lkml.kernel.org/r/1d03ee0d1b341959d4b61672c6401d498bff5652.1629386192.git.zhansayabagdaulet@gmail.com Signed-off-by: Zhansaya Bagdauletkyzy <zhansayabagdaulet@gmail.com> Reviewed-by: Tyler Hicks <tyhicks@linux.microsoft.com> Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@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.