7d4a93176e
Either ublk_can_use_task_work() is true or not, io commands are forwarded to ublk server in reverse order, since llist_add() is always to add one element to the head of the list. Even though block layer doesn't guarantee request dispatch order, requests should be sent to hardware in the sequence order generated from io scheduler, which usually considers the request's LBA, and order is often important for HDD. So forward io commands in the sequence made from io scheduler by aligning task work with current io_uring command's batch handling, and it has been observed that both can get similar performance data if IORING_SETUP_COOP_TASKRUN is set from ublk server. Reported-by: Andreas Hindborg <andreas.hindborg@wdc.com> Cc: Damien Le Moal <damien.lemoal@opensource.wdc.com> Signed-off-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com> Reviewed-by: ZiyangZhang <ZiyangZhang@linux.alibaba.com> Link: https://lore.kernel.org/r/20221121155645.396272-1-ming.lei@redhat.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.