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There are some issues about current io_sq_thread() implementation: 1. The prepare_to_wait() usage in __io_sq_thread() is weird. If multiple ctxs share one same poll thread, one ctx will put poll thread in TASK_INTERRUPTIBLE, but if other ctxs have work to do, we don't need to change task's stat at all. I think only if all ctxs don't have work to do, we can do it. 2. We use round-robin strategy to make multiple ctxs share one same poll thread, but there are various condition in __io_sq_thread(), which seems complicated and may affect round-robin strategy. To improve above issues, I take below actions: 1. If multiple ctxs share one same poll thread, only if all all ctxs don't have work to do, we can call prepare_to_wait() and schedule() to make poll thread enter sleep state. 2. To make round-robin strategy more straight, I simplify __io_sq_thread() a bit, it just does io poll and sqes submit work once, does not check various condition. 3. For multiple ctxs share one same poll thread, we choose the biggest sq_thread_idle among these ctxs as timeout condition, and will update it when ctx is in or out. 4. Not need to check EBUSY especially, if io_submit_sqes() returns EBUSY, IORING_SQ_CQ_OVERFLOW should be set, helper in liburing should be aware of cq overflow and enters kernel to flush work. Signed-off-by: Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com> Signed-off-by: Jens Axboe <axboe@kernel.dk> |
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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.