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From Artur: The wait_for_overlap wait queue is currently used in two cases, which are not really related: - waiting for actual overlapping bios, which uses R5_Overlap bit, - waiting for events related to reshape. Handling every write request in raid5_make_request() involves adding to and removing from this wait queue, which uses a spinlock. With fast storage and multiple submitting threads the contention on this lock is noticeable. This patch series aims to resolve this by separating the two cases mentioned above and using this wait queue only when reshape is in progress. The results when testing 4k random writes on raid5 with null_blk (8 jobs, qd=64, group_thread_cnt=8): before: 463k IOPS after: 523k IOPS The improvement is not huge with this series alone but it is just one of the bottlenecks. When applied onto some other changes I'm working on, it allowed to go from 845k IOPS to 975k IOPS on the same test. * md-6.12-raid5-opt: md/raid5: rename wait_for_overlap to wait_for_reshape md/raid5: only add to wq if reshape is in progress md/raid5: use wait_on_bit() for R5_Overlap Signed-off-by: Song Liu <song@kernel.org>
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.