TWx Linux Repository
f7eaacbb4e
While traversing the list, holding a spin_lock prevents load_buddy, making direct use of ext4_try_lock_group impossible. This can lead to a bouncing scenario where spin_is_locked(grp_A) succeeds, but ext4_try_lock_group() fails, forcing the list traversal to repeatedly restart from grp_A. In contrast, linear traversal directly uses ext4_try_lock_group(), avoiding this bouncing. Therefore, we need a lockless, ordered traversal to achieve linear-like efficiency. Therefore, this commit converts both average fragment size lists and largest free order lists into ordered xarrays. In an xarray, the index represents the block group number and the value holds the block group information; a non-empty value indicates the block group's presence. While insertion and deletion complexity remain O(1), lookup complexity changes from O(1) to O(nlogn), which may slightly reduce single-threaded performance. Additionally, xarray insertions might fail, potentially due to memory allocation issues. However, since we have linear traversal as a fallback, this isn't a major problem. Therefore, we've only added a warning message for insertion failures here. A helper function ext4_mb_find_good_group_xarray() is added to find good groups in the specified xarray starting at the specified position start, and when it reaches ngroups-1, it wraps around to 0 and then to start-1. This ensures an ordered traversal within the xarray. Performance test results are as follows: Single-process operations on an empty disk show negligible impact, while multi-process workloads demonstrate a noticeable performance gain. |CPU: Kunpeng 920 | P80 | P1 | |Memory: 512GB |------------------------|-------------------------| |960GB SSD (0.5GB/s)| base | patched | base | patched | |-------------------|-------|----------------|--------|----------------| |mb_optimize_scan=0 | 20097 | 19555 (-2.6%) | 316141 | 315636 (-0.2%) | |mb_optimize_scan=1 | 13318 | 15496 (+16.3%) | 325273 | 323569 (-0.5%) | |CPU: AMD 9654 * 2 | P96 | P1 | |Memory: 1536GB |------------------------|-------------------------| |960GB SSD (1GB/s) | base | patched | base | patched | |-------------------|-------|----------------|--------|----------------| |mb_optimize_scan=0 | 53603 | 53192 (-0.7%) | 214243 | 212678 (-0.7%) | |mb_optimize_scan=1 | 20887 | 37636 (+80.1%) | 213632 | 214189 (+0.2%) | [ Applied spelling fixes per discussion on the ext4-list see thread referened in the Link tag. --tytso] Signed-off-by: Baokun Li <libaokun1@huawei.com> Reviewed-by: Zhang Yi <yi.zhang@huawei.com> Link: https://patch.msgid.link/20250714130327.1830534-16-libaokun1@huawei.com Signed-off-by: Theodore Ts'o <tytso@mit.edu> |
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
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| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .pylintrc | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
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| 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 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.