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Worst case scenario of plist_add() happens when the priority of the inserted plist_node is going to be the largest after the insertion is done. The cost is going to be more significant when the original plist is longer, because the iterator is going to traverse the whole plist to find the correct position to insert the new node. The situation can be avoided by using a reverse iterator at the same time, doing so the maximum possible number of iteration is going to shrink from N to N/2. The proposed change of plist_add pasts the test in lib/plist.c to validate its correctness, also add the worst case scenario test for plist_add() in plist_test(). The worst case test are tested with the size of test_data and test_node growing from 200 to 1000. The result are showned in the following table, in which we can observed that the proposed change of plist_add performs better than the original version, and the difference between these two implementations are more significant with the size of N growing. The random case test [1], and best case test [2] are also provided, with result showing the proposed change performs slightly better in random case test while the original implementation performs slightly better in best case test, while the difference in both test are minor, we can see them as even in those two situations. ----------------------------------------------------------- | Test size | 200 | 400 | 600 | 800 | 1000 | ----------------------------------------------------------- | new_plist_add | 140911| 548681| 1220512| 2048493| 3763755| ----------------------------------------------------------- | old_plist_add | 188198| 774222| 1643547| 3008929| 4947435| ----------------------------------------------------------- Link: https://lkml.kernel.org/r/20240614154603.65203-1-richard120310@gmail.com Signed-off-by: I Hsin Cheng <richard120310@gmail.com> Signed-off-by: Ching-Chun (Jim) Huang <jserv@ccns.ncku.edu.tw> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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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.