Linux mainline fork with MSM8998 patches | https://mainline.space | Currently supported devices:
OnePlus 5/5T, Xiaomi Mi 6, F(x)tec Pro¹ (2019 QX1000 model) & Sony Xperia XZ Premium (UNTESTED!)
16b0c2581e
Currently we use a spin lock to protect the red black tree that we use to track block groups. Most accesses to that tree are actually read only and for large filesystems, with thousands of block groups, it actually has a bad impact on performance, as concurrent read only searches on the tree are serialized. Read only searches on the tree are very frequent and done when: 1) Pinning and unpinning extents, as we need to lookup the respective block group from the tree; 2) Freeing the last reference of a tree block, regardless if we pin the underlying extent or add it back to free space cache/tree; 3) During NOCOW writes, both buffered IO and direct IO, we need to check if the block group that contains an extent is read only or not and to increment the number of NOCOW writers in the block group. For those operations we need to search for the block group in the tree. Similarly, after creating the ordered extent for the NOCOW write, we need to decrement the number of NOCOW writers from the same block group, which requires searching for it in the tree; 4) Decreasing the number of extent reservations in a block group; 5) When allocating extents and freeing reserved extents; 6) Adding and removing free space to the free space tree; 7) When releasing delalloc bytes during ordered extent completion; 8) When relocating a block group; 9) During fitrim, to iterate over the block groups; 10) etc; Write accesses to the tree, to add or remove block groups, are much less frequent as they happen only when allocating a new block group or when deleting a block group. We also use the same spin lock to protect the list of currently caching block groups. Additions to this list are made when we need to cache a block group, because we don't have a free space cache for it (or we have but it's invalid), and removals from this list are done when caching of the block group's free space finishes. These cases are also not very common, but when they happen, they happen only once when the filesystem is mounted. So switch the lock that protects the tree of block groups from a spinning lock to a read/write lock. Reviewed-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: Filipe Manana <fdmanana@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com> |
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| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| 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.