mainlining shenanigans
be4c2d4723
When listing very large directories via NFS, clients may take a long time to complete. There are about three factors involved: First of all, ls and practically every other method of listing a directory including python os.listdir and find rely on libc readdir(). However readdir() only reads 32K of directory entries at a time, which means that if you have a lot of files in the same directory, it is going to take an insanely long time to read all the directory entries. Secondly, libc readdir() reads 32K of directory entries at a time, in kernel space 32K buffer split into 8 pages. One NFS readdirplus rpc will be called for one page, which introduces many readdirplus rpc calls. Lastly, one NFS readdirplus rpc asks for 32K data (filled by nfs_dentry) to fill one page (filled by dentry), we found that nearly one third of data was wasted. To solve above problems, pagecache mechanism was introduced. One NFS readdirplus rpc will ask for a large data (more than 32k), the data can fill more than one page, the cached pages can be used for next readdir call. This can reduce many readdirplus rpc calls and improve readdirplus performance. TESTING: When listing very large directories(include 300 thousand files) via NFS time ls -l /nfs_mount | wc -l without the patch: 300001 real 1m53.524s user 0m2.314s sys 0m2.599s with the patch: 300001 real 0m23.487s user 0m2.305s sys 0m2.558s Improved performance: 79.6% readdirplus rpc calls decrease: 85% Signed-off-by: Liguang Zhang <zhangliguang@linux.alibaba.com> Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com> |
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| Documentation | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| 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.