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When checking if a ticket was served, we take the space_info's spinlock. If the ticket was served (its ->bytes is 0) or had an error (its ->error it not 0) then we just unlock the space_info and return. This however causes contention on the space_info's spinlock, which is heavily used (space reservation, space flushing, allocating and deallocating an extent from a block group (btrfs_update_block_group()), etc). Instead of using the space_info's spinlock to check if a ticket was served, use a per ticket spinlock which isn't used by anyone other than the task that created the ticket (stack allocated) and the task that serves the ticket (a reclaim task or any task deallocating space that ends up at btrfs_try_granting_tickets()). After applying this patch and all previous patches from the same patchset (many attempt to reduce space_info critical sections), lockstat showed some improvements for a fs_mark test regarding the space_info's spinlock 'lock'. The lockstat results: Before patchset: con-bounces: 13733858 contentions: 15902322 waittime-total: 264902529.72 acq-bounces: 28161791 acquisitions: 38679282 After patchset: con-bounces: 12032220 contentions: 13598034 waittime-total: 221806127.28 acq-bounces: 24717947 acquisitions: 34103281 Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: David Sterba <dsterba@suse.com> |
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| .clang-format | ||
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| .editorconfig | ||
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| .pylintrc | ||
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| 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.