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When we check if we have work to run, we grab the acct lock, check, drop it, and then return the result. If we do have work to run, then running the work will again grab acct->lock and get the work item. This causes us to grab acct->lock more frequently than we need to. If we have work to do, have io_acct_run_queue() return with the acct lock still acquired. io_worker_handle_work() is then always invoked with the acct lock already held. In a simple test cases that stats files (IORING_OP_STATX always hits io-wq), we see a nice reduction in locking overhead with this change: 19.32% -12.55% [kernel.kallsyms] [k] __cmpwait_case_32 20.90% -12.07% [kernel.kallsyms] [k] queued_spin_lock_slowpath Reviewed-by: Hao Xu <howeyxu@tencent.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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.